Northeastern University
College of Engineering Department of Mechanical and Industrial Engineering Capstone Design Course
Adhesive Temperature Data-Logger
Submitted by Chris Hardy, Nick Lauder, Dustin Weir and Timothy Williams Date Submitted December 8, 2005 Course #/ Name MIMU702 / Capstone Design 2 Project Advisor Dinos Mavroidis, Ph.D. Sponsor McClellan Automation Capstone i
Abstract
This report outlines the development of a flexible temperature data-logger for McClellan Automation by a capstone design team at Northeastern University. The capstone group began with a technology developed by McClellan Automation of Bedford, NH to print thin, flexible circuits. The decision was made to develop a small, flexible, temperature data- logger which can be used to record temperature data of products such as blood, and various other refrigerated products in storage and transport. It has been determined that there is a clear market opportunity for such a device, and that McClellan’s technology is suitable for such a product.
McClellan Automation has the ability to print flexible polymer circuits on virtually any material, with very little waste or environmental consequences. Initial brainstorming revealed four major market opportunities which were researched by the team. The markets are: human wearable-military, human wearable-medical, sterilization validation, and temperature sensitive package transport. This report discusses these possible market applications through research of current products, patents, and professional literature.
Based on the research, the team originally decided to develop a human wearable temperature device, and outlined design criteria and anticipated challenges. The team then conducted a number of surveys with potential customers and found little use for the product as initially described. The team subsequently changed their application focus to the packaging industry, and more specifically the blood packaging industry, where there is both a market niche and a demand for the proposed product.
The team continued on to present several concepts for the design of the product. Design concepts were generated from customer needs and specification matrices which were created through interviews of various professionals in the field. The selected concept consists of a single temperature sensor inside housing that protects the circuit from outside elements. The specific components used to construct the device are outlined in detail in this report and include the printed circuit, surface-mount electrical components, polymer encapsulant, and adhesive.
The capstone group successfully completed the entire design process including market analysis, concept development, analysis, and testing. The group was successful in completing a fully-functional prototype, which measured and recorded the temperature profile of a bag of blood (simulated with saline). The recommendations for the future improvements of this device are also outlined in this report. Capstone ii
TABLE OF CONTENTS
Abstract...... i Table of Contents...... ii List of Tables ...... iv List of Figures...... v List of Equations...... vii Nomenclature...... viii 1 Mission Statement...... 1 2 Significance...... 2 3 Background...... 3 3.1 McClellan’s Technology...... 3 3.2 Application Selection...... 3 3.3 Human Wearable - Military...... 4 3.4 Human Wearable - Medical...... 7 3.5 Sterilization...... 10 3.6 Packaging of Medical/Perishable Goods ...... 11 4 Customer Needs...... 15 4.1 McClellan Automation’s Needs...... 15 4.2 Problem Statement Development ...... 15 4.3 Interviews / Needs Assessment...... 16 4.4 Design Specifications...... 17 5 Concepts...... 21 5.1 Geometries ...... 21 5.1.1 Single Sensor ...... 21 5.1.2 Multiple Sensors (Embedded)...... 22 5.1.3 Multiple Sensors (Remote) ...... 23 5.2 Housing Options ...... 23 6 Concept Selection ...... 26 7 Component Descriptions...... 27 7.1 Component Scheme ...... 27 Capstone iii
7.2 Substrate...... 27 7.3 Coating...... 28 7.4 Adhesive ...... 29 7.5 Circuit ...... 30 7.5.1 Circuit Requirements ...... 30 7.5.2 Prototype Circuit...... 31 7.5.3 Component Selection...... 34 7.6 Software ...... 36 8 Circuitry Development...... 39 8.1 Overview...... 39 8.2 Prototype Development ...... 39 8.2.1 Breadboard Prototype I...... 39 8.2.2 Breadboard Prototype I...... 40 8.2.3 Through-hole Soldered Prototype...... 40 8.2.4 Home-etched Prototype ...... 41 8.2.5 Final Printed Prototype ...... 41 9 Thermal Analyses ...... 42 9.1 Thermal Model...... 42 9.2 Convective Coefficients for Air and Blood ...... 44 9.3 First Order Thermal Model Approximation ...... 45 9.4 Blood Temperature Time Response...... 46 9.5 Modeled Temperature Profile...... 47 10 Testing...... 51 10.1 Thermal Testing...... 51 10.1.1 Blood Bag Testing ...... 51 10.1.2 Temperature Calibration ...... 51 10.1.3 Time Calibration ...... 55 10.2 Data Logger Testing ...... 55 10.3 Discussion of Results...... 56 11 Cost Analysis ...... 59 12 Project Results ...... 60 Capstone iv
12.1 Goals Summary...... 60 12.2 Recommendations...... 60 13 References...... 62 Appendix A: Thermal Calculations ...... 65 Appendix B: Final Circuit Subcomponents ...... 78 Appendix C: Final Prototype Circuit ...... 79 Appendix D: Final Cable Circuit ...... 80 Appendix E: Temperature Calibration Test Results ...... 81
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List of Tables
Table 3.1: Human wearable – medical, available products summary ...... 7 Table 4.1: Customer needs list...... 17 Table 4.2: Metrics list ...... 18 Table 4.3: Needs-metrics matrix...... 20 Table 6.1: Concept selection matrix ...... 26 Table 7.1: Loctite Hysol US5502 Liquid Urethane Encapsulant specifications ...... 29 Table 7.2: 3M VHB tape properties...... 29 Table 7.3: Selected surface mount prototype subcomponents...... 34 Table 7.4: Battery options...... 35 Table 9.1: Air properties at 300K ...... 44 Table 9.2: Blood properties with 30% hematocrit levels...... 44 Table 11.1: Per-board cost analysis ...... 59 Capstone vi
List of Figures
Figure 3.1: NASA Ames Astrobionics CPOD...... 4 Figure 3.2: Example WPI sensor ...... 5 Figure 3.3: Sensors integrated into soft belt ...... 5 Figure 3.4: Patent sketch of a variation device flexible electronic unit...... 6 Figure 3.5: Ambulatory Monitoring MicroMini-Motionlogger...... 8 Figure 3.6: BodyMedia SenseWear patient monitoring armband ...... 8 Figure 3.7: Nexan Limited portable patient telemonitoring system with a memory card ...... 9 Figure 3.8: LifeMinder system ...... 9 Figure 3.9: KSW-TempSens™ and Specifications...... 12 Figure 3.10: Technopuce Actitag and Specifications ...... 12 Figure 3.11: Dallas Semiconductor-Ibutton...... 13 Figure 3.12: Example of Signatrol’s SL150 and SL151 tags and product specifications ...... 4 Figure 3.13 (above): SL51T, SL52T, SL53T Temperature Data logger ...... 14 Figure 3.14 (left): SL51T, SL52T, SL53T Temperature Data logger specifications ...... 14 Figure 4.1: Temperature Sticker Indicator...... 18 Figure 5.1: Single Sensor concept sketch ...... 21 Figure 5.2: Multiple Sensors (Embedded) concept sketch...... 22 Figure 5.3: Multiple Sensors (Remote) concept sketch...... 23 Figure 5.4: Circuit components sealed with adhesive fabric on outside...... 24 Figure 5.5: Fabric removed, showing robust polymer seal and external sensor...... 24 Figure 5.6: Circular sticker, with gasket to seal components ...... 25 Figure 5.7: Gap for placement of sensors ...... 25 Figure 7.1: Component layout ...... 27 Figure 7.2: 3M VHB Adhesive Transfer Tape F9473PC specifications ...... 30 Figure 7.3: Original Dallas Semiconductor DS1615 demonstration circuit...... 32 Figure 7.4: Subdivided circuit plan...... 33 Figure 7.5: PowerPaper Battery...... 35 Figure 7.6: DS1615/DS1616 Evaluation Software mission control screen...... 36 Figure 7.7: DS1615/DS1616 Evaluation Software line graph of data...... 37 Capstone vii
Figure 7.8: SolidWorks model of custom designed connector...... 38 Figure 7.9: Photograph of data logger and connector...... 39 Figure 8.1: Breadboard Prototype I ...... 39 Figure 8.2: Breadboard Prototype II ...... 40 Figure 8.3: Cable Circuit...... 40 Figure 8.4: Through-hole Prototype ...... 40 Figure 8.5: Circuit Tracer Pattern ...... 41 Figure 8.6: Final Printed Prototype...... 41 Figure 8.7: Six Prototypes Constructed ...... 41 Figure 9.1: Equivalent thermal circuit for composite material...... 42 Figure 9.2: Heat transfer rate model ...... 43 Figure 9.3: Plots the temperature of the blood vs. time...... 47 Figure 9.4: Theoretical blood and sensor temperature response...... 48 Figure 9.5: Blown up section of spiked temperature ...... 49 Figure 9.6: Delta temperature ...... 50 Figure 9.7: Percent error of the temperature at the sensor location...... 50 Figure 10.1: Labview interface for temperature measurements ...... 51 Figure 10.2: A syringe was used to measure out the appropriate amount of saline solution...52 Figure10.3: Blood bag clamp...... 52 Figure 10.4: Blood bag response from 0 degrees Celsius to room temperature...... 53 Figure 10.5: Temperature of hanging bag...... 53 Figure 10.6: Sample temperature calibration results ...... 54 Figure 10.7: Plot of data downloaded from data logger ...... 55 Figure 10.8: Thermal Response superimposed with the test data...... 56 Figure 10.9: Theoretical blood temperature response...... 57 Figure 10.10: Data logger temperature vs. LabView blood temperature ...... 58 Figure 12.1: Barcodes located on a blood bag label ...... 61 Capstone viii
List of Equations Equation 9.1a: Heat transfer input equation ...... 43 Equation 9.1b: Heat transfer output equation ...... 43 Equation 9.2: Steady state heat transfer balance...... 43 Equation 9.3: Rayleigh number calculation...... 44 Equation 9.4: Nusselt number calculation (1)...... 45 Equation 9.5: Average convective coefficient calculation ...... 45 Equation 9.6: Nusselt number calculation (2)...... 45 Equation 9.7: Grashof number calculation ...... 45 Equation 9.8: Prandlt number calculation...... 45 Equation 9.9: Biot number calculation ...... 46 Equation 9.10: Average blood temperature approximation...... 46 Equation 9.11: Blood temperature calculation...... 46 Capstone ix
Nomenclature
Symbol Description Units 2 hbB B Convective coefficient for blood W/mP KP 2 ha,B hB airB B Convective coefficient for air W/mP KP
qinB B Heat rate in W
qoutB B Heat rate out W
TsensB B Temperature at sensor location K
TbB B Blood Temperature K
Ts,1B B Inner Blood Bag Surface Temperature K
Ts,2B B Outer Blood Bag Surface Temperature K 3 ρ Density kg/mP P
2 µ Dynamic viscosity Nsec/mP P
cpB B Specific heat kJ/kgK 2 υ Kinematic viscosity mP /secP ω Frequency Rad/sec K Thermal conductivity W/mK W Power W m Meter m 2 g Gravity at sea level m/sP P 2 Average convective coefficient W/mP KP h Ra Rayleigh number - Gr Grashof number: ratio of buoyancy to viscous forces - Pr Prandlt number: ratio of momentum and thermal diffusivities - Nu Dimensionless temperature gradient at the surface -
TinfB B Ambient temperature K
TairB B Air temperature K
RTB B Total thermal resistance K/W
(TinfB )B ◦B B Initial ambient temperature K
TAB B Amplitude temperature K
TfilmB B Film temperature K Vbatt Battery supply voltage relative to ground V Vcc Communications voltage supply relative to ground V Vdrvin Output power supply voltage from the computer V Gnd Ground reference voltage V
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1 Mission Statement
The Capstone Design team is developing an adhesive, flexible, robust, temperature data- logger that incorporates flexible circuit technology from McClellan Automation. The focus of the design is to create the packaging that will house the circuit. Developing the final circuit to meet the needs of the customer is beyond the scope of the project, but the group will utilize a substitute circuit to prove the applicability of the packaging to the market and provide McClellan Automation with a working prototype for sales purposes.
The design team’s goals are to develop a small, lightweight, inexpensive, flexible, and durable product that may be used for numerous applications. The team made the decision to focus on utilizing this technology to monitor and verify temperature of refrigerated products, specifically blood and blood products during storage and shipment. This path was chosen in order to make the best use of the circuit technology’s potential. Capstone 2
2 Significance
Blood and blood products are shipped all over the country to blood banks at hospitals as well as to remote areas of the world designated as disaster zones. The Food and Drug Administration (FDA) requires that blood and blood products be maintained at specified temperatures during storage and shipment. This product would allow the Red Cross and other blood organizations to verify that each container of their blood products has been maintained at the FDA’s specified temperatures.
Currently, small devices exist that monitor and store temperature; however, these devices are either too large or too expensive for regular use. Instead, a few are used periodically throughout the year to verify the storage and transportation processes. McClellan Automation’s temperature data logger will be designed to be cost effective to allow users to adhere this device to almost every container.
According to the American Association of Blood Banks (AABB) approximately 15 million units of whole blood and red cells were collected in 2001, and the volume of blood transfused is growing at approximately 6% per year [1]. This provides McClellan Automation with a large market opportunity to utilize its flexible circuit technology in a product that monitors and verifies the temperature of blood and blood products during storage and shipment. Capstone 3
3 Background
3.1 McClellan’s Technology
McClellan Automation is an engineering company that specializes in large scale automation solutions for companies in various industries. The capstone design team was presented with a set of printed circuit negatives in an on-site meeting with project sponsor, Mr. James McClellan. The purpose of the circuits is to measure and record 8 different inputs. The circuit pattern, software for operating the circuit, memory for recording data, a power supply, and a temperature probe are being developed by Dr. Ed Berg, using his own patented circuit printing technology. The group was asked to research a market application for this technology (in whole or in part) and demonstrate a complete, profitable product.
The technology consists of printing conductive circuit patterns, using standard printing techniques, on almost any surface. Current standard circuit printing processes involve etching agents and solvents, which would destroy many circuit substrates including paper, cloth, cardboard, etc. Dr. Berg’s process is said to keep such substrates intact. The technology is also environmentally friendly. The chemicals used in the process are reasonably benign, and the technology allows for very little waste of these chemicals, which saves cost.
3.2 Application Selection
The design group began to refine the problem statement from ideas generated during a brainstorming meeting about potential applications. Some ideas resulting from that meeting were:
• A device to measure ambient conditions around biological samples, produce, blood, transplant organs, and other packaged materials during transit • A human-wearable device to sense temperature as a biological indicator of disease, pregnancy, or reactions to medications • A human-wearable device to record ambient and body temperature as a physiological indicator of soldier status during battle and training • Incorporating a self-destructing circuit into single-use medical devices to assure the single-use condition • Incorporating a device into a package to be sterilized to validate the sterilization process • A device to measure failure indicators of mechanical components such as helicopter rotor joints
The market research was broken down between individual team members to evaluate 4 potential markets: human wearable for medical applications, human wearable for military applications, packaging, and sterilization.
The information in this background section of the report was determined by the design team at the conclusion of Capstone I. It is an examination of the market landscape for each of the Capstone 4
initial four project description concepts. It does not include the interviews or research into the demand for a product, it only contains the results of the current state of the market.
3.3 Human Wearable – Military
A lightweight, low powered, data logging device with the ability to monitor the vital signs of a soldier, and transfer this information wirelessly to a central unit, would allow medics and squad leaders to make better decisions based on their knowledge of the health of soldiers. The Warfighter Physiological Status Monitoring (WPSM) program run by the U.S. Army funds projects to develop soldier monitoring devices. The US army has a goal to utilize these devices to reduce the morbidity of soldiers [2].
Presently, research is being conducted to integrate devices that provide a medic with the physiological status of the soldiers that he is responsible for. The existing monitoring devices being developed integrate wireless data transmission to allow real-time, continuous monitoring a soldier’s vital signs.
This goal must be achieved without limiting the performance of the soldier and adding weight to his gear. A soldier must be able to fire his weapon and maneuver quickly while on the battlefield. The current devices must be “acceptable to the soldier,” and shouldn’t “degrade the mission performance,” [2]. Researchers working for the WPSM program, feel that the most difficult challenges will be due to the fact that the sensor is being used in harsh environments [2]. For this reason, companies are utilizing the latest technology such as integrating electro-textiles into athletic shirts.
NASA Ames Astrobionics team developed the “CPOD” a wearable monitoring system that records or wirelessly transfers data via Bluetooth connection to a central PC (see Figure 3.1). The device was originally developed to monitor astronauts on extreme missions; however, the team is also pursuing this device for numerous markets including military applications [3, 4]. This technology was found on NASA’s website. No US patents were found on this product.
Figure 3.1: NASA Ames Astrobionics team’s CPOD used to The CPOD unit is considered a store and wirelessly transmit human physiological data [3, 4]. lightweight system that is worn on a belt around the waist and Capstone 5
“performs signal conditioning and data acquisition, data logging, data transmission, and status display,” for up to 9 hours of monitoring [3, 4]. The CPOD is designed to accurately monitor:
• ECG (Electrocardiogram, heart • Heart Rate
muscle activity) • Pulse Oximetry (SpO2B )B • Respiration • Diastolic and Systolic Blood • Activity (3-axis acceleration) Pressure [3, 4] • Skin/Ambient Temperature
The CPOD successfully monitors numerous vital signs of a soldier; however, the size of the unit could interfere with a soldier’s ability to perform important tasks like firing his weapon from a prone position. Another drawback of the system being used for military application is that the device has cable connections from the sensors to the CPOD. These wires can become tangled and caught during its usage impeding the soldier’s movements. [2, 3, 4]
Worcester Polytechnic Institute (WPI) is working with the Warfighter Physiological Status Monitoring (WPSM) program for the U.S. Army to develop lightweight sensors that will transmit data wirelessly to squad leaders and medics. Yitzhak Mendelson of WPI, is developing small wireless sensors “to monitor pulse rate, skin temperature, and arterial oxygen saturation,” such as the one in Figure 3.2 [5]. He states that the most difficult challenges will be designing his sensor to withstand the harsh environment a soldier will face, and attachment of Figure 3.2: Example the sensor to the skin [5]. WPI sensor [5].
A United States’ Soldier carries approximately 90 pounds of equipment. Of that weight, 30 to 50 percent is accounted for by batteries. Therefore, the crucial requirement of the monitoring device is that it must not add weight. Because of this, it should be integrated into the current soldier system, and not require much power [5].
Seeing the need for such a product, Foster-Miller has been overseeing the development of a Warfighter Physiological Status Monitoring (WPSM) system integrated into the soldier’s current outfit. This is due for completion in 2006. The system will provide vital information of the soldier’s condition, and wirelessly transmit this information to the squad’s medic. The Figure 3.3: Sensors integrated into soft sensors are sewn into a soft belt and integrated with belt [3, 4] the “army issued” undergarment (See Figure 3.3) and measure the following [3, 4]: • Skin Temperature • Breaths taken • Heart Rate • Ballistic impact Capstone 6
Foster-Miller’s goals are to produce a system that will allow the soldier to conduct his tasks and survive the harsh environment. The WPSM is designed to be flexible and out of the soldier’s way. The WPSM system must withstand the soldier’s environment such as: abrasion, sweat, blood, dirt, salt, cold, and moisture [3, 4].
The future advancements of Foster—Miller’s WPSM system will integrate sensors into a wearable garment such as an athletic shirt using technology being developed at Malden-Mills known as electro-textiles. Electro-textiles involve inter-working conductive fibers into the fabric [3, 4]. The benefit of this design is that there is negligible added weight to the system.
A flexible adhesive sensor for human-wearable applications has been patented by The Regents of the University of California. It is an “Electronic Unit Integrated into a Flexible Polymer Body” (US Patent 6,878,643). This product is not commercially available at this time. The electronic unit consists of a flexible polymer body used with a Micro-Electro- Mechanical System (MEMS) sensor that has applications including, but not limited to, military, consumer, and medical.
The MEMS sensors that can be incorporated into the device that are most relevant to a human wearable product are:
• Temperature Sensing • Weather Sensing • Vibration & Acceleration Sensing • Humidity and Moisture Sensing • Gas Sensing
The device is considered a “peel and stick” system, which can adhere to any curved surface for application, and is considered a low cost electronic system with low cost production methods. Figure 3.4 is a patent sketch of the unit. The patent describes it as a “flexible unit similar to the clear ‘peel and stick’ tags garages place on an automobile’s windshield after the car has been serviced to remind the owner of the automobile when the next servicing is due.” [6]
One of the variations of the product described by the patent states, “A MEMS sensor is integrated into the flexible polymer body. A processor chip is operatively connected and integrated into the flexible polymer body. A battery provides power to the processor chip and the MEMS sensor. The processor chip and the MEMS sensor are connected by the Figure 3.4: Patent sketch of a variation device flexible metallization system.” [6] electronic unit [6].
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The design is very versatile. The device has an integrated antenna for wireless data transmission. It can be used in many applications integrating numerous sensors, and it has the ability to adhere to most surfaces. The electronic device is a rugged system that is able to function in severe climates such as water submersion or extreme temperatures. The device can also incorporate off-the-shelf components, and can therefore integrate low cost products into its system [6]. However, this patent does not appear to utilize polymer circuit printing as an option. This may limit the surface features it can adhere to since the circuit is rigid.
The current human wearable devices being developed monitor many more vital signs than surface skin temperature. However, it is clear that there is a market opportunity for a flexible temperature-monitoring device because it adds no weight to the system, requires little power, and is very inexpensive.
3.4 Human Wearable – Medical
Another potential market for this printable circuit technology is a human wearable skin temperature data logger for the medical field. This type of device could be utilized in the following areas where skin temperature is an important health indicator:
• Research studies and drug trials • Before or after medical procedures including surgery • Detection of certain conditions such as Raynaud’s phenomenon or diabetes • Monitoring ovulation of women with pregnancy difficulties
Raynaud’s phenomenon and diabetes, both mentioned above, are conditions where a key symptom is a constriction of blood vessels in the extremities causing them to become cold. Being able to continuously monitor the temperature of a patient’s fingers or toes could allow for better detection of the condition. [7, 8] Another application is to measure a woman’s body temperature fluctuations, which can indicate ovulation and help increase the chances of pregnancy [9].
There are already a few human wearable products on the market for measuring temperature. Most measure other parameters in addition to skin temperature, which usually makes them bulky and expensive. Table 3.1 below shows a summary of companies that are currently marketing wearable products which measure skin temperature.
Table 3.1: Human wearable – medical, available products summary Company Product Description Patents Ambulatory Monitoring, Inc. (Ardsley, NY) Sleep study motion logger and sensors N/A BodyMedia (Pittsburgh, PA) Body monitoring system with armband 6,527,711 Nexan Limited (Cambridge, UK and Atlanta, GA) Portable patient monitoring system 6,416,471, 6,454,708
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Ambulatory Monitoring, Inc. specializes in devices for monitoring sleep patterns. The products that they offer are very similar to a wristwatch in size and shape, and can have many different sensors installed depending on the information being gathered. Figure 3.5 shows one of Ambulatory Monitoring’s products with three possible sensors: temperature, light and sound. Although they do offer a skin temperature measurement, the primary sensors offered are an accelerometer and a light sensor to measure sleep patterns of a person participating in a sleep study [10]. The drawback to this product is the size, Figure 3.5: Ambulatory Monitoring MicroMini- and the level of user discomfort. Motionlogger and three sensors, temperature, sound and light [10] BodyMedia, Inc. offers patient monitoring armbands. The armband contains five sensors that measure skin temperature, ambient temperature, heat flux, galvanic skin response, and acceleration. An example of one of these armbands can be seen in Figure 3.6. A software package is sold with the armband, which uses the collected data to calculate calories burned, duration of exercise, energy expenditure, and sleep duration. The armbands are marketed for both research studies, and for personal use in weight-loss and exercise programs [11, 12]. This product has the following drawbacks:
• Complication of use • Size and weight (3.4 in x 2.1 in x 0.8 in, 2.8 oz.) • Battery life (up to 14 days of measurements)
Figure 3.6: BodyMedia SenseWear patient monitoring armband [11]
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Information about the products offered by Nexan Limited could only be found in the patents themselves as the company does not have a website listing information. Therefore, it is unknown if there is a commercial product available. The patents describe a portable patient monitoring system, which has the capability to measure full waveform ECG Figure 3.7: Nexan Limited portable patient telemonitoring system (Electrocardiogram, heart with a memory card [13] muscle activity), respiration, skin temperature and motion. The two patents listed in Table 3.1 refer to the two variations of the product, which differ slightly in the type of memory used to store the recorded data. The system involves a disposable patch, which is attached to the patient’s chest. The patch is wired to a unit on the patient’s waist, which either stores the data using a memory card (Patent 6,454,708) or wirelessly transmits the data to a computer up to 60 meters away (Patent 6,416,471). The design is obtrusive, and complicated. A schematic of the device on a patient taken from the patents can be found in Figure 3.7 [13, 14].
Two other skin temperature-monitoring systems were found, although neither was related to a specific company. The first system, dubbed LifeMinder, uses a wristband about the size of a watch, which is wired to a sensor band on the index finger to make measurements. These measurements include skin temperature, movement, pulse, and galvanic skin response. The data from these measurements is sent via Bluetooth to a PDA (Personal digital assistant). The software on the PDA will use the collected data along with other pre-programmed functions to remind the user when to eat, sleep, exercise, or take medications. Figure 3.8 shows a schematic of the LifeMinder on a person [15]. LifeMinder is very complex, obstructive, and expensive. The last claim, in terms of device cost, is related to the cost of a standard PDA of at least $200 [16].
The second device found without a specific company Figure 3.8: LifeMinder system [15] was developed and patented Capstone 10
(Patent 6,847,913) by doctors and engineers at Johns Hopkins University in Baltimore, MD. The device is a flexible band that is attached to a patient’s finger, which measures and records both skin and ambient temperature. The device was developed as a research tool specifically for observing patients with Raynaud’s phenomenon. As mentioned previously, Raynaud’s phenomenon has the symptom of constricted blood vessels in the extremities, which causes them to become cold. The only drawbacks to this design are its limited use; it is designed to be attached to a finger, and it is not water resistant [17]. This product is also not offered commercially, and was developed to aid researchers at Johns Hopkins in studying Raynaud’s phenomenon.
3.5 Sterilization
The capstone design group examined the possibility of using a device to validate sterilization of packages by measuring and reporting the conditions inside a package. Some research was conducted into common methods for sterilizing medical devices. The four most popular methods are ethylene oxide gas (ETO) sterilization, moist heat (steam) sterilization, electron beam sterilization, and gamma ray sterilization [18]. Each method was found to have specific measurable qualities which could validate the process (i.e. radiation dose, temperature, gas concentration, humidity).
Sterilization of all medical devices sold in the US is governed by the Food and Drug Administration (FDA), which requires the validation of all processes used to sterilize medical devices. 21 CFR Section 211.113(b), Control of Microbiological Contamination states: "Appropriate written procedures, designed to prevent microbiological contamination of drug products purporting to be sterile, shall be established and followed. Such procedures shall include validation of any sterilization process [19]." The actual method for validating the sterilized products is not outlined directly in the FDA published documents. Although not specifically required, the published guidelines for industry and FDA staff contain references to many ISO standards.
Currently the validation for many sterilized products is guided by nine ISO standards: three general, one each specific to ETO, radiation, and liquid chemical, and three specific to moist heat. These standards require sampling of sterilized lots to confirm the sterilization level, or probability of receiving an infection from contact with the product. These standards guide the sampling of the sterilized product to ensure the effectiveness of the process [20].
Additionally, a company may choose to use chemical or biological indicators to show the proper sterilization conditions have been met. Chemical indicators contain various chemicals that typically change color when one or several environmental conditions have been met. Biological indicators contain live spores resistant to the sterilization process, and can be tested to confirm the effectiveness of the process [21].
In using either chemical or biological indicators, the company must have access to the results of the test. This may mean putting the indicator on the outside of the package, or it may mean designing a transparent package for color-changing indicators. It is not currently possible to confirm the state of an indicator inside an opaque package. Capstone 11
Currently there are no products on the market or standards referring specifically to the use of an electronic sterilization indicator. There is currently one patent, 6,485,979, which describes an electronic device that can read information relating to the effectiveness of a sterilization process, and (according to claim 6) transmit that information via RFID technology [22]. However, this patent does not exclusively limit the creation of a device which transmits the exact conditions inside the sterilized package at certain time measurements.
In summary, there is an open niche for a product which directly measures the conditions of the inside of a sterilized package and transmits the measurement data through the package using a non-optical method. There are no products that fit this market, and there is one applicable patent which doesn’t completely exclude the capstone group from the market. There is a need, as required by the FDA, to prove the validity of a sterilization process, and there are several standards, which outline the environmental conditions that a device would have to measure. There are currently indicators on the market that such a product would compete with, but the group’s initial concepts have advantages over these devices.
3.6 Packaging of Medical/Perishable Goods
A major market opportunity that exists for the use of cheap, flexible circuit technology is the time-temperature verification of transported goods. The goods could include medical products, blood, organs to be transplanted or perishable food products that require refrigeration. In either case, companies can verify the temperature history of goods shipped with an inexpensive temperature data logger.
Several competitive commercial devices have been found, which measure and store temperature data during shipping of medical and food products. Most involve RFID data transmission of stored data, and some incorporate an adhesive backing for attachment onto product packaging. Some are disposable, and others designed to be reusable.
KSW-Microtech of Germany makes the TempSens™, which is the most similar to a product that would be designed using the polymer printing technology. KSW claims that its product is thin, flexible, inexpensive, disposable, and can be used to log the temperature of transported pharmaceutical/medical and food products over time. Figure 3.9 is a marketing picture of the device.
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Figure 3.9: KSW-TempSens™ and Specifications[23]
No US patents have been found to protect the manufacture of this product, however, US patent 6,764,004 claims a “logistics chain management systems…” and specifies KSW- TempSens™ as “a preferred data logger for temperature monitoring…”. An obvious drawback is that this product can only store 64 time-temperature data points.
Technopuce, of France, manufactures a temperature logger for product transport; however, it is not a single-use device. It is more bulky and more expensive than KSW-TempSens™ (See Figure 3.10).
Figure 3.10: Technopuce Actitag and Specifications [24]
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Again, no US patents could be found protecting this temperature data logging product as a unit, however US patent 6,593,669 (in the name of Technopuce International) claims “a battery cell and a method of producing the cell” for the product.
Dallas Semiconductor manufactures a product called Ibutton, which can be purchased for $15 per unit. The device measures and records temperature over time and has an adhesive backing to stick to product packaging. The devices are not flexible or thin like KSW- TempSens™ and Technopuce-Actitag™ (See Figure 3.11 below).
Figure 3.11: Dallas Semiconductor-Ibutton [25]
Signatrol Data Logging Solutions, based in the UK, have developed small data loggers that monitor the temperature of food, pharmaceutical, blood and blood product shipments. The SL150 and the SL151, Figure 3.12 on the following page, are examples of their current product. These tags have a four year battery life, and a temperature range of -30° C to 70° C with an accuracy of +/-0.5° C. The tags have separate readers to download the information wirelessly to a database. The system can be set up to monitor “alarm conditions” where the product it is monitoring has been subjected to temperatures outside of the specified range.
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Figure 3.12: Example of Signatrol’s SL150 and SL151 temperature monitoring tags and product specifications [26]
Signatrol also released the SL51T, SL52T, and SL53T (See Figure 3.13) that can also be used to monitor the temperature profile.
Figure 3.13 (above): SL51T, SL52T, SL53T Temperature Data logger [26]
Figure 3.14 (left): SL51T, SL52T, SL53T Temperature Data logger specifications [26]
This product is a single channel temperature data logger that is only 17mm in diameter and 6mm high made from stainless steel, and only weighs 4 grams. The temperature sensor can detect from -40° C to 85° C or 0° C to 125° C depending on the model, and can record up to 8,000 points. Figure 3.14 is Signatrol’s specification for this model. Capstone 15
4 Customer Needs
4.1 McClellan Automation’s Needs
As stated, McClellan Automation would like to develop a product based on their flexible circuit technology. McClellan, a company that specializes in the design of automated medical manufacturing equipment, hopes to diversify its business with the manufacture of a stable product. The key benefits of the technology should be utilized including low-cost, high-manufacturability, flexibility, and low-profile. These aspects were considered highly in the decision making process.
4.2 Problem Statement Development
The capstone design team has decided to design a temperature data logger for monitoring the temperature of packages in transit or storage such as donated blood and food. It has been determined through the market research outlined in this report, that there are pursuable opportunities in each of the four previously described areas. Designing a human wearable device, the team will have to meet more stringent criteria. By designing to a high standard, this product will be adaptable to other markets such as sterilization or packaging. For military applications there are currently advanced products being developed, and if the companies are successful in developing these all-inclusive human wearable devices, it will be a difficult market for McClellan to compete in.
The capstone group received feedback from several professionals in the medical field who felt that human wearable skin temperature sensors could be useful in research. However, it was determined that skin temperature cannot be reliably correlated to core body temperature, and that core body temperature was generally more useful than skin temperature. Because this correlation cannot be made, skin temperature was said to provide limited information most medical applications where temperature is a factor. Furthermore, medical research that uses skin temperature was determined to be a low-volume application that is not well suited to the low-cost, high-volume capability of McClellan’s flexible circuit technology.
Dr. Paolo Bonato of Spaulding Rehabilitation Hospital in Boston, MA, stated that although skin temperature measurement was limited, other parameters such as acceleration would be useful. He described the need for such a product in work with Parkinson’s patients who need objective measurements of bodily accelerations while away from the doctor’s office. However, he also expressed that a device requiring continuous measurement, such as an accelerometer, would need a larger power source such as a battery pack that would be worn on the patient’s waist. This would be possible with the thin printed circuit technology; however it would not present any advantage over a device such as BodyMedia’s SenseWear. It also would not take advantage of the strengths of the printed circuit technology, i.e. thickness, flexibility, and price.
The capstone team also determined that there is an opportunity for developing a sterilization verification sensor due to the fact that there are not many products available for this Capstone 16
application. However, a sterilization sensor would require the development of new sensors, and would not be easily adapted to any other market because of the high temperatures the team would design to. Sterilization verification therefore does not satisfy the requirements of the capstone group.
Presently, there are several products available for monitoring the temperature profile of products in transit. A product utilizing the circuit technology from McClellan Automation would have a tremendous advantage over the competition because of the cost and environmental reasons. In addition, because there are virtually no feasible devices to monitor the temperature profile of blood during shipment and storage, there is a perfect niche in this market for a thin, flexible, inexpensive temperature data logger.
The market landscape led our capstone group to rule out the sterilization validation concept and the military wearable concept. Through the group’s additional interviews and research into the medical wearable application, the team found that although the market is open for such a device there wasn’t a demand for the application in the field. The packaging concept has both a market niche and demand in the field.
Considering the capabilities and requirements of the capstone group, the problem statement has been refined to develop packaging for a temperature data logger which houses flexible circuit technology to be used to monitor and verify temperature of products during shipment and storage.
4.3 Interviews / Needs Assessment
The first step in order for the capstone group to develop a marketable product for McClellan Automation was to become familiar with the needs of potential customers. The team contacted the American Red Cross, the American Association of Blood Banks (AABB), the FDA, Brigham and Women’s Hospital, and Children’s Hospital for information on how they control and monitor temperature of their blood products. The team also contacted Jeremiah Hoffman, senior project engineer at Gorton’s located in Gloucester, MA, as a secondary user who processes and distributes frozen fish products.
The FDA supplied the capstone team with “Title 21—Food and Drugs, sections 600 to 799,” which includes requirements for shipping, storing, handling, and processing blood and blood products. The team used this specification to learn about the types of environments the device may encounter [27].
The goal of the interviews was to learn the customers’ and users’ real needs by asking each interviewee a set list of questions, which we expanded upon during the discussion. The following is a list of general questions discussed with the interviewees:
Capstone 17
• How critical is it that blood and blood products (or other temperature sensitive products) need to be kept at a specified temperature? • Walk us through how you currently verify/monitor temperature of blood and blood products (or other temperature sensitive products)? o Frequency of measurements o Accuracy of current system o Continuous monitoring o Length of time product stored/transported o Container temperature • Do you like the current system? • Is the system robust enough? • How reliable is the monitoring system? • What do you dislike about the current monitoring system? • What improvements would you make to the current monitoring system?
4.4 Design Specifications
In order to organize and document the information found in the interviews, the capstone team generated a needs list, seen below in Table 4.1. This list continues to grow as more interviews are being held. The list, called the “customer needs list”, is a compilation of needs from all the end users that the team spoke with.
Table 4.1: Customer needs lists [28]. No. Need Imp. Small enough to not take up more space on package/Thin enough 1 to go under label 5 2 Covers all temperature ranges 3 3 Very inexpensive (less than $1) 5 4 User Friendly 4 5 Product will last life of container 3 6 Wireless Data Transmission 3 Using RFID to incorporate Bar code information. Currently 5 bar 7 code stickers are on blood & blood product bags. 3 8 Easy Data Retrieval 4 9 Measurement frequency 2 10 FDA approved materials 4
After creating the customer needs list, the team ranked the needs on a scale of one to five under the importance column, one being the least important and five being a critical aspect to the design. For example, many customers expressed that a similar device would be used if it were an inexpensive unit. As a result, the team ranked “very inexpensive” as a five, indicating a high priority.
From the customer needs list the capstone team took each “need” and linked it to a metric (unit) that addressed that need. The metrics are listed in Table 4.2. The list states what unit Capstone 18
will be used when developing that aspect of the design. For example, the need that states “minimize mass” is associated with kilograms [kg], and both are listed in the same row of the metrics list. The metrics were also ranked on a scale of one to five according to their importance.
Table 4.2: Metrics list, [28]. Metric No. Metric Imp. Units 1 Cost of production 5 $/unit 2 Chip Memory Size 3 kb 3 Temp Sensor Resolution 2 mA/Deg C 4 High Stress Polymer Substrate 3 N/m^2 5 Maximize Lifting Force / Adhesive Capability 3 N 6 Minimum Bend Radius 3 m 7 Quick attachment 3 XX 8 Minimize Mass 4 kg 9 Simple Data Retrieval 4 ** 10 Minimize Battery Power Decay during Container life 3 Watts 11 60 Day Life 3 s 12 External Application 5 ** 13 No Jagged Edges 4 ** 14 Circuit Functions @ -25C to 37C 5 deg C 15 Battery Power functions at cold temperatures 3 Watts 16 Frequency 1cycle/10 min 2 cycles/min 17 Minimize Sufrace Area 2 m^2
As shown in Table 4.2, one of the most important findings is that the overall cost of the unit will be a deciding factor whether the product will be widely used on every blood bag that is being shipped and stored. Nancy Higgins, the temperature control technician at Brigham and Women’s hospital blood bank specifically stated that they cannot use their color changing temperature indicators on every blood bag because they simply do not have the budget for it. This product, shown in Figure 4.1, is currently sold at $1.00 per unit.
Figure 4.1: Temperature Sticker Indicator [29].
Capstone 19
The team determined from the discussion with Ms. Higgins that developing the lowest cost temperature data logger on the market would provide McClellan with a very high volume of orders. If the losses from bad products during shipment or storage is less than the cost of incorporating a temperature system to monitor or verify that their products have been maintained at the proper temperature requirements, than the user will not see a need for the temperature sensing device.
The team also determined that external application is a high priority. The FDA specification, section 640.2 (b) Blood container, indicates that nothing can contaminate the inside of the blood and blood products container. As a result, it was determined this was a non-negotiable constraint and by attempting to incorporate the temperature data logging device into the current container would put too much risk on this constraint. It was decided that developing the device which adhered to the outside of the container it would eliminate this unnecessary risk and make the product more versatile.
The capstone group spoke with Mr. Michael Dragone, the Regulatory Manager of the Red Cross for the New England region. He was very interested in the concept of the product for monitoring blood in shipment and storage. He also shed some light on the process used currently for verifying the temperature history of the units of blood. The workers at the donation centers, and at the various spots that the blood stops at before it arrives at the large central processing center periodically check the temperature in the transporters that the blood bags are carried in by using a thermometer. Mr. Dragone mentioned that although failures are rare, they do happen, and that he would be interested in a better method or data collection if it were available and inexpensive enough.
The group also held a conference call with Jeremiah Hoffman, the senior project engineer at Gorton’s seafood in Gloucester, Massachusetts, a secondary user. He described the state of the seafood industry as similar to the blood industry: the shipping and storage processes are verified with large, expensive measurement equipment until enough confidence in the process is gained to trust the product is arriving without significant “temperature abuse.” The equipment must then be found and returned to Gorton’s for download. In Mr. Hoffman’s opinion, a small, inexpensive temperature measurement device with wireless download would be valuable to his company.
After consulting these customers and organizing and ranking their needs a metrics list was constructed. The metrics developed from the needs lists can be graphically illustrated in a need versus metrics chart shown in Table 4.3.
Capstone 20
Table 4.3: Needs-metrics matrix [28]. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 e lif
ty ntainer o pabili s ring c p Ca C e s du v i s ld tem to 37
tric o dhe C ate in r a at c l Me e wer Decay a r t lution ubst ns v o n o at -25 o S e /10m ie s e P l Force/A ze tr ns y i c ion nti m Radius ation t es e u Re u rial d er c
ing no t f ch i e ss n rface A t t ry S e u a edg ta a 1 c ta R t Lift pplic odu a B S B Ma mo a M ensor ed e e e r m pr ze Life o Funct i z z z e i power i u y S r nal a le D m a of k t uency Me p m i mi e uit t i x ic c s jagg ip ter D nim nim nim n a i i i u h 0
Needs Co C Tem Poly M M Q Mi Simp M 6 Ex No Cir Batt Freq M 1 Low Cost xxx 2 Indicates when Product falls outside temp range x 3 Adheres to package xx 4 Flexible xx 5 Monitors Temperature x 6 Easy to attach x 7 light weight x 8 Simple Data Retrieval x 9 Battery Lasts life of storage xx 10 Battery last life of shipment xx 11 Device Lasts life of Container xx 12 Cannot contaminate product xx 13 Application Suitable for Temperature Range xx 14 Suitable Measurement Frequency x 15 uncolored & transparent container x
This matrix indicates what metrics correspond to each need. Ideally one metric should correspond to one need, but it can be shown that some metrics overlap more than one need. For example, it is shown that the need for a low cost unit is dependent on some of the expensive items such as cost of production, chip memory and temperature sensor resolution. Capstone 21
5 Concepts
5.1 Geometries
Based on the customer needs discussed in the previous section, and what is known about the circuit being used by McClellan Automation, basic prototype geometries were laid out. These were useful in assessing the basic benefits and drawbacks of several different designs, and also as a design tool for identifying the key components of the device.
5.1.1 Single Sensor
Figure 5.1: Single Sensor concept sketch.
This simple design embeds the temperature sensor and electronics in a pocket in the center of an adhesive patch. The electronics are shielded from the environment by thick layers of transparent plastic. The outer housing is made up of two pieces of flexible plastic or cloth glued together. Although the electronics are modular, the assembly of the entire device is final, and if it does not function properly it must be discarded, not repaired.
This design could also incorporate a removable plastic cartridge for increased modularity, which would house the electronics. The cartridge would be comprised of the circuit, battery, temperature sensor, and other electrical components sealed between two layers of transparent plastic to protect from the environment. The removable section would be implantable into any base structure. This would allow for easy replacement of the electrical components if they should malfunction, or if the product needs to be monitored for longer than the battery life.
Capstone 22
Benefits: • Simple design • Cheapest design • Modular design (with removable cartridge option) • Option of extending device lifespan by replacing cartridge and combining data files
Drawbacks: • Only one measurement point • Extra cost to create removable cartridge, which may not be necessary
5.1.2 Multiple Sensors (Embedded)
Figure 5.2: Multiple Sensors (Embedded) concept sketch.
This design utilizes the eight possible sensor inputs on the circuitry. Again, the electronics are embedded in a transparent plastic casing to seal them from the environment. The eight temperature sensors are embedded in the outer package of the device with internal wires running to the central electronics. The lifespan of this product would be eight times shorter unless the frequency and/or total number of data points taken were reduced.
Benefits: • More measurement locations for better average data • Wires and sensors internal to increase durability
Drawbacks: • More expensive due to number of sensors • Patch less flexible overall Capstone 23
• Lifespan, frequency of measurements, or total number of measurements must be reduced to meet power requirements
5.1.3 Multiple Sensors (Remote)
Figure 5.3: Multiple Sensors (Remote) concept sketch.
This design incorporates the same central electronics sealed from the environment. It also utilizes the eight sensor inputs as the previous design. The only difference with this concept and the previous one is that the eight sensors and connecting wires are external to the central patch. Each sensor has its own small adhesive patch. This enables the user to place the eight sensors in a desired pattern to measure multiple locations on the same product, or multiple small products within one package.
Benefits: • Ability to measure at desired locations, or multiple small products within a larger package • Multiple sensors give a more accurate average
Drawbacks: • More expensive due to number of sensors • Lifespan, frequency of measurements, or total number of measurements must be reduced to meet power requirements • External wiring could become tangled or disconnected from sensor
5.2 Housing Options
This variation of the single sensor design shown in Figure 5.4 has the temperature sensor on the outside of the sealed circuit components, and the adhesive fabric encases the sealed circuit component housing. This design addresses the concern that our temperature sensor Capstone 24
will not be capable of measuring the core temperature of the blood contents or ambient temperature if the sensor is enclosed in the polymer circuit housing because polymers generally do not have a high thermal conductivity.
Figure 5.4: Circuit components sealed with adhesive fabric on outside.
The first advantage of this design is that a robust polymer material is to be used for added strength on the two sides of the seal, while maintaining flexibility, shown in Figure 5.4. The gasket (Shown in Figure 5.5 in blue) is used to protect the circuitry from the environment. For example, at sub freezing temperatures moisture may freeze inside the circuitry container damaging the device. Additionally, at low temperature condensation will freeze to the exterior of the product and any thawing that may occur will allow moisture to enter the circuit housing.
The most significant aspect of this design is that the temperature sensor is positioned on the exterior of the sealed circuit housing. The reason for this is that polymer materials are not good thermal conductors; therefore, positioning the sensor inside the sealed circuit might affect the true measurements, or the time response of the temperature sensor. The polymers will act as an insulator and the temperature sensor may not read the proper temperature. It may take too long for the system to reach equilibrium to read the proper temperature due to the poor thermal conductivity of polymer materials. A thermal analysis must be conducted to Figure 5.5: Fabric removed, showing robust polymer seal and external sensor. verify this.
This design specifically monitors the ambient temperature that each container is experiencing. The sensor is not specifically measuring the contents’ temperature because the contents are inside a polymer container; therefore, the same problems arise.
The disadvantages of this design are that the blood or blood product may be subjected to ambient temperatures above the specified temperature range for a short period of time, yet the contents inside the container may actually be still within the FDA specified temperature Capstone 25 range. The gasket and the robust polymer material may also limit the overall flexibility of the device.
The next design demonstrates a similar concept by positioning the circuitry inside a sealed polymer housing and positioning the temperature sensors outside to read the ambient temperatures, shown in Figure 5.6.
Gasket
Figure 5.6: Circular sticker, with gasket to seal components.
In this design, the circuitry is printed directly on the base of the temperature unit and the surface mount components are attached to this surface. The solid state temperature devices are placed outside the sealed circuit housing between the fabric materials. Again, this design will be measuring the ambient temperature instead of monitoring the contents of the container. This space is shown in Figure 5.7 below.
Space between fabric materials
Figure 5.7: Gap for placement of sensors. Capstone 26
6 Concept Selection
The selection of a design concept was done both quantitatively and qualitatively. The details of each design concept were considered and compared. Categories to compare the different deigns were created and listed, as shown in the table below as “Selection Criteria”. Each of the designs was then ranked in each category, the scores totaled, and the designs were ranked by total score. By comparing the designs in this manner, the design team was able to compare the options objectively.
Table 6.1: Concept selection matrix [28] Embedded External External Selection Single Multiple Multiple Sensor Sensor Criteria Sensor (Embedded) (Loose) (Circular) (Square) Ease of Use 0 0 -1 0 0 Measurement Accuracy -1 1 1 -1 -1 Flexibility 0 -1 0 0 0 Cost 1 -1 -1 0 0 Lifespan 1 -1 -1 1 1 Surface Area 1 -1 -1 0 0 Robustness 0 -1 -1 -1 -1 Time Response 0 1 1 1 1 Mass 0 -1 -1 0 0 Lift Force 0 1 0 1 0 Net Score 2 -3 -4 1 0 Rank 1 4 5 2 3
Based on the table above, the concept to pursue is the first design listed, the “Embedded Single Sensor”. The main categories where this design has an advantage over the external sensor designs are robustness and cost. The design with the internal sensor will be more robust because there will be no chance of disconnection of the most important component, the temperature sensor. This design will also be slightly less expensive to manufacture because the step of extending the connection for the temperature sensor outside the sealed circuit will not be necessary. Capstone 27
7 Component Descriptions
7.1 Component Scheme
The final product will have four main components: a circuit, a substrate, an adhesive, and a protective coating (See Figure 7.1 below). The goal is to optimize the substrate, the adhesive, and the protective coating. Since a circuit is already under development by McClellan Automation, the capstone group will specify a circuit that will be suitable to test these three other main components on the product. This preliminary proof of concept prototype will not be optimized for customer needs, but it will provide McClellan with a device they can use for sales purposes while they develop their circuitry. When this is complete, McClellan can swap the proof of concept circuit with the optimized circuit and have a fully optimized product.
32.768 kHz Crystal DS1615 Temperature Surface Mount Logging Chip Resistors
Urethane Coating
Batteries and Holders Substrate
Tabs for Data Transfer Adhesive Backing (Under)
Figure 7.1: Component layout
7.2 Substrate
The flexible circuit that incorporates Ed Berg’s printing technology is printed on Mylar film. This will be the material used by McClellan Automation on future generations of the temperature data logger. However, because the technology of flexible solder connections to connect the surface mount components to the circuit board will take too long to develop, the capstone group was instructed to complete the proof of concept prototype with a more traditional circuit printed on 1/16 in. thick FR4 substrate. FR4 is a standard printed circuit board material that is used in almost every electronic device, and is easily identified by its green color. This type of circuit will allow for more traditional solder connections, and will allow for testing that the circuit itself works. It will also allow for testing of the polymer coating and adhesive, which are described in detail in the following sections.
7.3 Coating Capstone 28
The polymer coating used to protect the circuitry and surface-mount components of the temperature data-logger was chosen based on a few basic criteria. The most important of these criteria is the varied temperature range that the data-logger will see. This includes high temperatures that a product might see if in transit in a truck moving on a desert highway. The other extreme is for products that must be frozen for shipment and storage. Blood and blood products are shipped at both refrigerated and freezing temperatures depending on the component being shipped. For example, fresh frozen plasma must be shipped and stored at or below –18oC [27]. This is done by packing the plasma with dry ice in insulated boxes for shipment. The temperature of dry ice is around –80oC [30]. The more important of these two temperatures (high and low extremes) is the low. This is because most polymers perform well at room temperature and above, and don’t lose elasticity and flexibility unless exposed to lower temperatures.
The coating needs to protect the electronics of the device from the light wear and tear that the product will see, as well as other environmental conditions such as humidity and static electricity that could damage the circuitry. The coating needs to do these things while remaining relatively flexible at the extreme low temperature of –80oC.
The other basic criteria that need to be met are the color and ease of use. McClellan Automation requested that the coating not be transparent for two reasons. The first reason is that an opaque coating could hide the design of the circuitry and help to prevent other companies from copying the technology. In addition, making the device aesthetically pleasing for end-users is a concern. The last major criterion is ease of use. Because these data-loggers will eventually be mass-produced by McClellan Automation, it is important that the coating be easy to apply, with a curing process that is neither complex nor lengthy.
Several materials were considered, ranging from two-part epoxies to silicones and urethanes. The capstone group decided to use a two-part urethane (resin and catalyst) from Loctite. The deciding factor for this product was the low temperature performance. Because of the extremely low glass-transition temperature of the material (-77oC) it should remain flexible even at dry-ice temperature [31]. The other specifications of this material can be found in Table 7.1 on the following page. Capstone 29
Table 7.1: Loctite Hysol US5502 Liquid Urethane Encapsulant specifications [31] Application Characteristics Viscosity cps @25oC 1300 Working Time 125 g mass @ 25oC <30 min. Gel Time 125 g mass @ 25oC 65 min. Cure Cycle Normal @25oC 24-48 hrs Alternate @60-85oC 3-6 hrs. Color Black Density g/cc 1.26 Mix Ratio by weight Resin/Catalyst 11.5/88.5 by volume Resin/Catalyst 1.0/7.0 Typical Cured Properties Hardness Shore A 45 Coefficient of Thermal Expansion In/in/oC 1.83 x 10-4 Glass Transition Temperature oC <-77
This product is used primarily for encapsulating circuit boards. It has a relatively high viscosity, meaning that application is mainly by pouring it onto the circuit components to be covered. However, it is possible to thin the liquid with a solvent and spray it for thin, even coating and faster processing for mass-production applications. The capstone group will experiment with both methods of application to determine which is best.
The curing of this particular urethane can be done at room temperature or by heating, which speeds up the cure time (24 hours at room temperature versus 3-6 hours at 60-85oC). The fact that this liquid does not need very specific curing conditions (Temperature, humidity, gas concentration, or UV light) is an advantage. However, because only atmospheric conditions are needed for curing, once mixed the liquid must remain sealed to the environment to prevent premature solidification [31].
7.4 Adhesive The adhesive to attach the temperature data-logger to a product needs to fit the same basic criteria as the polymer coating. The most important of these is the extreme low temperature of dry ice (-80oC) for the same reasons listed in the previous section.
Table 7.2: 3M VHB tape properties [32] Property Value The adhesive must be able to adhere the Adhesive Thickness 0.010 in. substrate of the flexible circuit, as well as the prototype FR4 circuit board, and to Liner Thickness 0.004 in. varied product surfaces at this low Coefficient of Thermal Expansion 0.77 %/oC temperature. Thermal Conductivity 0.0016W/cm oC The adhesive needs to have a certain Peel Adhesion to Stainless Steel 9.0 lb/in degree of ease of use, for the Normal Tensile to Aluminum 100 lb/in2 manufacturing process, as well as the end Capstone 30
user. The best solution for this criterion is a double-sided adhesive tape that could be easily incorporated into an automated production and easily used by the customer, who would simply peel off the paper cover, and stick the data- logger to the product.
The capstone group surveyed several adhesives and tapes and decided to use a 3M double-sided adhesive tape. The specifications of this tape can be found in Table 7.2. Like the polymer coating, the deciding factor was the low temperature performance. The tape o performed well at –54P CP in tests performed by 3M. The results of these tests can be found in Figure 7.2 This is a Figure 7.2: 3M VHB Adhesive Transfer Tape F9473PC lower temperature than most other specifications [33] adhesives on the market, and the capstone group will run testing of its o own at the dry ice temperature of -80P C.P This adhesive tape has an approximate list price of $109.81 per 3 in. wide, 60 yd. long roll. This is a cost of $0.04 per data-logger assuming the circuit size is 1 ½ inches square. This cost does not include any discount for large quantity orders.
7.5 Circuit
7.5.1 Circuit Requirements
The capstone group was able to locate a temperature data logger circuit that will meet the requirements of the proof of concept prototype. The proof of concept circuit must:
• Measure and record temperature • Be able to download the temperature data to a PC for processing • Be small and flexible • Meet the health requirements of the FDA • Operate within the full temperature range of the target products • Be inexpensive • Contain readily available subcomponents
The proof of concept circuit will serve as a placeholder for a more complex circuit to be designed in the future that will better meet the identified needs of the consumer. It was requested by McClellan Automation to serve as a concept prototype that they can use for Capstone 31
sales purposes, and to prove the substrate, adhesive, component mounting method and encasement material will all be transferable to the final product.
The future circuit will have the following requirements: • All proof of concept requirements • Wireless data download • Non-volatile memory (flash, magnetic, etc.) • Additional write/download memory for donor data and tracking o • Accurate measurements to within 0.1P CP
7.5.2 Prototype Circuit
The chosen temperature data logger circuit is based around a Dallas Semiconductor integrated circuit, the DS1615. The IC contains nearly all of the capabilities to measure, record, and download temperature data on the chip. It is available in a small 16-pin surface mount package, and has a suitable operating temperature range. As far as we can tell, there are no other all-in-one temperature data logger IC chips available on the market. Dallas Semiconductor has designed a circuit and software for companies to demonstrate the abilities of their chip. The circuit and software is available to the public, free of charge, from their website, www.dalsemi.com, and can be found in Figure 7.3.
For the purposes of the capstone course and the final prototype the circuit design, in its entirety, will be treated as an off-the-shelf component. It was chosen for its low cost, small and common subcomponents, pre-existing free download and analysis software, and knowledgeable product support from Dallas Semiconductor. It will be modified to meet every requirement of the proof of concept circuit as previously outlined. Capstone 32
Figure 7.3: Original Dallas Semiconductor DS1615 demonstration circuit Capstone 33
The capstone group divided this circuit into three sections: components that are necessary for temperature measurement and data recording (Core Circuit), components that are used only during chip programming and data download (Cable Circuitry), and components that demonstrate the ability of the DS1615, but are not necessary to meet the requirements of the proof of concept circuit (Extra Test Circuitry). Figure 7.4 shows the original circuit broken into these 3 areas.
Figure 7.4: Subdivided circuit plan Capstone 34
7.5.3 Component Selection
For the extra test circuitry and cable circuitry, thru-hole mount components were chosen to meet the specifications in the circuit first on their availability, and next on their price. Effort was also made to find components from as few vendors as possible, and with minimum quantities suitable for prototyping. Since these components will typically only operate at room temperature, minimum operating temperatures were not examined.
Two sets of components were specified for the core circuitry. One set is all thru-hole components for breadboard prototyping, and one set is ultra-small surface mount components for the etched tracer version. All components meet the specified requirements of the original Dallas Semiconductor test circuit, and they meet the expected operating temperatures of the circuit. The final components were chosen from as few vendors as possible, to meet reasonable minimum quantities for prototyping, and lastly by their price. The expected subcomponents of the final circuit prototype are contained in Table 7.3 below. The entire components list can be found in Appendix B.
Table 7.3: Selected surface mount prototype subcomponents Ref. Description Vendor P/N Qty/ Board $/ea Min. Qty. D4 3.6V Battery V364 2 $0.62 1 D4a Battery Holder 2998 2 $0.59 1 R3 10K Resistor 9C12063A1002FKHFT 1 $0.09 10 R5 100K Resistor 9C12063A1003FKHFT 1 $0.09 10 U2 Temp. Recorder IC DS1615S 1 $15.13 1 X1 32.768 kHz, 6pF Crystal CM200S 1 $0.88 1
The DS1615 integrated circuit is one of two temperature-sensing chips made by Dallas Semiconductor that include all sensing, filtering, communications, memory, and control circuits on a single chip. The other IC, DS1616, is larger, provides no more memory than the DS1615, and the surface mount package has an operating temperature of 0° C to 70° C, which doesn’t cover the operating range of the final product.
The CM200S crystal meets the requirements of the chosen circuit, meets the operating temperature requirements, and is available in an extremely small surface mount package.
The resistors were chosen for the same reason: they are extremely small surface mount components, they meet the circuit specifications, and they meet the operating temperature values.
Batteries were chosen to meet the voltage and current requirements of the DS1615 IC chip. The temperature requirements were of particular concern because many batteries lose voltage potential at our lower temperature limit. The manufacturer of the DS1615 IC chip specifies the battery voltage to in the range of 2.7 volts and 4.5 volts. Using lifetime equations given in the data sheet and a minimum of 1 minute between temperature measurements, the capstone group determined the average current draw to be 1.7µA. Therefore, a battery capacity of 15 mAh was determined to be sufficient for the lifetime of the product. The group explored many options for the battery (see Table 7.4). Capstone 35
Table 7.4: Battery options Model # Type Manufacturer Voltage Diameter Height Capacity Temp [mm] [mAh] Range Lir1620 Lithium Ion Powerstream 3.7 16 2.2 11 -20 to 60 C 5 Zinc Air Duracell 1.4 5.8 2.15 42 0 to 50 C STD-3 Proprietary Powerpaper 1.4 39 square <1 30 -20 to 60 C CR1025 Manganese Dioxide Varta/Panasonic 3 12.5 1.6 27 -20 to 65 C Lithium BR1216 Polycarbonmonofluoride Panasonic 3 12.5 1.6 25 -30 to 80 C Lithium 364 Silver Oxide Energizer 1.55 6.8 2.15 20 -10 to 65 C
One option was to use 3.7 volt lithium ion batteries; however the available sizes were not desirable. The capstone group also found an acceptable battery from PowerPaper (see Figure 7.5). These batteries are thin, flexible, and can be stacked to produce the desired voltage. The only drawback is that the footprint of their standard batteries is about the same size as the target of the entire temperature sensing product. The group determined the batteries to be too large, but recommends future development with PowerPaper to manufacture a smaller, L-shaped battery that can fit within the desired Figure 7.5: PowerPaper Battery footprint of the product.
The capstone group decided to use three 1.5 volt batteries, in series, to produce 4.5 volts to the chip. With 4.5 volts, any voltage loss due to temperature or spiked current will not bring the total voltage below the 2.7 volts necessary to power the DC1615 IC chip. Very small “coin” batteries at 1.5 volts are widely available. The group chose Energizer’s 364 because of good size, temperature characteristics, and flat voltage/time curves. Also, three small batteries will be more flexible than one large one.
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7.6 Data Transfer
7.6.1 Software
The software, “DS1615 / DS1616 Evaluation Software”, version 2.001, is supplied free of charge by Dallas Semiconductor, and available from their website, www.dalsemi.com. It communicates with the DS1615 via the computer’s parallel port. Through this software, the user can specify the frequency of measurements, the time until the measurement starts, the high and low alarm thresholds, the start time stamp, and a short character string. The temperature of the last measurement is displayed and updated real-time. The user can also download the temperature data to disk, and view the data in either a histogram or a line graph format.
Figure 7.6: DS1615/DS1616 Evaluation Software mission control screen Capstone 37
Figure 7.7: DS1615/DS1616 Evaluation Software line graph of data
7.6.2 Data Download
Data download is accomplished through a cable which was redesigned from the original DS1615 circuit layout. All components necessary for communication have been incorporated into the junction box on the cable. The group also designed and fabricated a custom connector to interface with the data logger. The connector can be seen in figures 7.8 and 7.9. An LED illuminates when a positive connection has been made. A switch inside the connector assures that the pins are in contact with the data logger before cable power is switched on.
There is only three things a user must do to communicate with the data logger. First, the user must plug the RS232 connector to the communications port on the computer running the software. Next, the user must slide the connector onto the data logger. Finally, the user must execute the software. These steps can be performed in any order. Capstone 38
Figure 7.8: SolidWorks model of custom designed connector
Figure 7.9: Photograph of data logger and connector Capstone 39
8 Circuitry Development
8.1 Overview
A series of five prototypes were planned for testing and development. Each stage had specific objective to prove in the operation of the circuit. The prototypes were as follows: a breadboard prototype of the original circuit, a breadboard prototype of the circuit as modified by the capstone team, a through-hole soldered prototype, a home etched version of the designed circuit tracer pattern, and a number of professionally printed circuit boards.
8.2 Prototype Development
8.2.1 Breadboard Prototype I
The first prototype was used to prove the operation of the software and to debug communication between the computer and the chip. The circuit, shown in Figure 8.1, below, is built to the specifications of the original circuit plan obtained by Dallas Semiconductor. The circuit was to be initialized by the computer and then disconnected at the DB9 connection at the computer. During this remote operation, the circuit was powered by a 4.5 volt DC power supply at Gnd and Vbatt.
The software initially returned an error “Chip cannot be found”, and the circuit board was examined. Two rails on the breadboard which power the circuit were assumed to be connected, and were found not to be. They were then connected, but the error remained. The power input voltage from the computer (ground to Vcc wires) fluctuated during software initialization, so the com port (com 2) was assumed to be correct. Since the DS1615 chip requires a 10% difference between Vcc and Vbatt, Vbatt was reduced from 4.5 volts to 3 volts (above the specification of 2.7 volts). The communication was successful. Vbatt was increased in increments of 0.1 volts until communication failed between 3.8 and 3.9 volts. The power supply was set to 3.5 volts for the Figure 8.1: Breadboard Prototype I remainder of the experiment.
The circuit was initialized and ran for 5 minutes while connected to the computer, and the data was downloaded. The measured data all seemed reasonable. The chip was then Capstone 40
initialized, disconnected from the computer, and left connected to the power supply set to 3.5 volts overnight. The next morning a reasonable, consistent temperature curve was downloaded from the chip.
The specified batteries operate at a combined voltage of greater than 3.5 volts, so using the cable circuitry in combination with the specified batteries would block communication. A variable voltage regulator was specified as a replacement for U3 show in Figure 7.3. Due to the efficiency of the voltage regulator, the approximate maximum measured output is 5.3 volts, which will work with the total estimated battery voltage of 4.5 volts.
8.2.2 Breadboard Prototype II
A second breadboard prototype was made, (Figure 8.2), to verify that the “core circuit” could operate correctly without the “cable circuitry,” as indicated in Figure 7.4. The “core circuit” and “extra test circuitry” were disconnected from the cable circuitry, and the cable circuitry was connected to this second prototype by a cable.
Communication was not successful on the first trial, and the batteries were found to be producing greater than their specified voltage. When only two batteries were connected in series, however, the voltage fell within the correct operating range of the circuit. The circuit design was then changed to include only two 1.5 volt batteries. Figure 8.2: Breadboard Prototype II 8.2.3 Through-hole Soldered Prototype
Next, the voltage regulator system was integrated into the cable system, and a soldered through-hole prototype cable and core circuit was made (Figures 8.3 and 8.4, respectively). Three 5-minute missions were conducted. Two of the missions failed. The chips had been reset sometime in between disconnect and re-establishing communication.
Since the data point history was not reset (a characteristic Figure 8.3: Cable Circuit of power loss to the chip), noise to the Vcc pin during disconnect was the suspected reason for the chip reset. A micro-switch was added to Vdrvin to terminate power to the system until all connections have been made. A light emitting diode and 1KΩ resistor were also added between the output of this switch and ground, to indicate when the power is turned on to the cable. This solved the problem of the resetting chips. Each time the circuit is to be connected to the cable, it is to be done so before the power is activated. Before the chip is to be disconnected, the power must be turned off. Figure 8.4: Through-hole Prototype Capstone 41
8.2.4 Home-etched Prototype
The capstone team outsourced the design of a printed circuit board to a Northeastern University graduate, since the team didn’t have access to the proper software. The specified surface mount components were laid out on a 1.5” x 1.5” board, and tracers and connection surfaces were specified. This was done just before the third battery was removed from the circuit plan, so a jumper was added in place of the second battery. The Figure 8.5: Circuit Tracer Pattern circuit tracer pattern in Figure 8.5 is drawn to scale. (Drawn to scale) The team attempted to manufacture the pattered circuit board by masking off the appropriate tracers on a copper-clad FR4 board and submerging it in a ferric chloride solution. Using a conductive ink pen to repair some damaged tracers, a working board was successfully produced approximately one week before the delivery of the professionally printed boards. Due to the aesthetics of the home-etched prototype, the timing of the delivery of the outsourced boards, and to save the limited number of subcomponents in stock, the capstone team did not solder to these boards.
8.2.5 Final Printed Prototype
Figures 8.6 and 8.7 show the final prototypes printed by MSG Corporation. They arrived pre-masked with solder, on 1/32” thick fiberglass (FR4) board. A total of six prototypes were hand populated by the capstone team. The maximum overall dimensions are 1.5” x 1.5” x 0.16” They were each tested by running a 34 hour mission and downloading the data using the through-hole soldered cable previously constructed (Figure 8.3). Figure 8.6: Final Printed Prototype
Figure 8.7: Six Prototypes Constructed Capstone 42
9 Thermal Analyses
The theoretical analyses were beneficial to increase the Capstone team’s understanding of the critical parameters of each component and allow the team to optimize these areas of the design based on the results. The analyses are also critical to the development of the product because the results will provide a comparison to testing data. Certain tests cannot be conducted and as a result the theoretical testing is critical to the product development.
9.1 Thermal Model
A thermal analysis has been conducted to verify that the temperature sensor is actually measuring the temperature of the blood bag. A one-dimensional thermal conduction resistance analysis was used to model the thermal conductivity through the device. When the blood is secured in the blood bag it is assumed to be at approximately body temperature, or approximately 37°C. If it were immediately placed in a cooler on ice the ambient temperatures will be approximately 0°C. Hence, these are the initial temperature conditions assumed for blood and air, respectively. These conditions were assumed because this is the largest temperature difference the blood should theoretically ever experience during shipment and storage.
Figure 9.1 is the equivalent thermal circuit for a composite material. Each component of material in the device has some amount of thermal resistance, so this resistance can be modeled as an electrical resistance. 1
ha A T T q” b s,1 Tsens Ts, 2 out
q”in Ta, ∞ 1 L1 L2 L3 L4 k A k A k A k A hb A 1 2 3 4 1 h A r Figure 9.1: Equivalent thermal circuit for composite material.
The fundamentals of heat transfer state that heat is transferred from high temperature to low temperature. In our analysis heat is initially being transferred from the warm blood to the cooler ambient air, at approximately 0°C. If a small differential control area is taken around the temperature sensor location it can be shown that heat is entering and leaving the ∆T temperature sensor location, qinB =qB outB ,B where the heat transfer rate is q = , Figure 9.2. [33] ΣR Capstone 43
Figure 9.2: Heat transfer rate model 1 qin = ⋅ (Tb − Tsens ) E9.1a R1 1 qout = ⋅ (Tsens − Tinf ) E9.1b R2
where R1B B and R2B B are the thermal resistances from the blood to the sensor location, and from the sensor location to the ambient air respectively. The lengths, L1B B through L4B B are the corresponding thicknesses of each component in the device. The thermal conductivity values, k1B B through k4B B are the values for each component in the device respectively. The heat flux q’’inB B and q’’outB B is the energy transfer by way of heat through the control volume.
As a result, the temperature at the Sensor location was solved for by setting equations E9.1a and b equal to each other and solving for TsensB ,B which is shown below.
T T b + inf R1 R2 Tsens = E9.2 1 + 1 R1 R2
All of the properties for the fluids were determined at the film temperature, TfilmB ,B which is the average of the temperature of the fluid at the surface and the temperature of the entire fluid. Air properties were determined at the temperature of 300K, room temperature, for simplicity at this stage. The physical properties of air at 300K are shown in Table 9.1: Capstone 44
Table 9.1: Air properties at 300K [33] Kinematic Dynamic Viscosity, Density, Specific Heat Viscosity, Thermal Conductivity, 7 6 3 µ ⋅10 P (N*s)/m^2P Ρ (kg/m^3) cpB (kJ/kg*K)B υ ⋅10 (m^2/s) K ⋅10 (W/m*K) 1.1614 1.007 184.6 15.89 26.3
The properties of blood were located from internet sources, and provided in Table 9.2. The properties of blood are dependent on the amount of hematocrit levels in blood. Hematocrit is the volume percent of whole blood that is composed of red blood cells. The properties were taken at approximately 30% hematocrit.[34]
Table 9.2: Blood properties with 30% hematocrit levels. [34]
Kinematic Specific Dynamic Viscosity, Thermal Density, ρ Heat Viscosity, Conductivity Prandlt 3 6 (kg/m^3) (kJ/kg*K) µ ⋅10 (N*s)/m^2 υ ⋅10 (m^2/s) (W/m*K) Number 1.002 3.936 1.416 1.413 0.496 11.24
The blood bags are made from PVC with an added plasticizer for flexibility. The material properties could not be obtained from the blood bag manufacturer so a thermal conductivity value was determined from general flexible PVC material, which was determined to W be 0.147 , and a thickness assumed to be 0.5 mm. [34] The 3M VHB Adhesive m 2 ⋅ K Transfer Tape F9473PC material properties can be seen from Table 7.3. The substrate will be FR4 material. The actual properties were determined from FR4 suppliers to be 0.268 W -3 . The thickness of the FR4 was assumed to be 1.6*10P P m (1/16 in); however, the m ⋅ K -4 actual PCB will be thinner at 7.9*10P P m (1/32 in). [35] The thinner FR4 thickness will decrease the thermal resistance, only making the heat rate transfer through the device better. Lastly, the urethane material’s thermal conductivity was provided by the manufacturer to be W 0.3 [31]. m 2 ⋅ K
9.2 Convective Coefficients for Air and Blood
First, the convective coefficients needed to be approximated. For air, the convective coefficient was determined by assuming free convection over a horizontal plate. The Rayleigh number is simply a product of the Grashof and Prandtl number, which correlates the relative magnitude of the buoyancy and viscous forces in the fluid. The Rayleigh number was determined:
ρ 2βgc ∆TL3 Ra = p E9.3 µK
2 Where ρ is the density of air, β is 1/TFilmB ,B g is gravity at sea level, 9.81 m/sP ,P cpB B is the specific heat of air, µ is dynamic viscosity, K is the thermal conductivity, and finally ∆T=(TsB -TB infB ),B Capstone 45
where TsB B is the surface temperature and TinfB B is the fluid temperature. The convective coefficient of air was evaluated by determining the Nusselt number, Nu, which is a dimensionless temperature gradient at the surface in a fluid:
n Nu = C(Ra) E9.4
Where, C and n are constants, and equal 0.54 and 0.25 respectively. The convective coefficient can be determined as shown below:
Nu ⋅ K h = E9.5 L where h is the average convective coefficient. The convection coefficient of air was W determined to be approximately h = 7..16 a m2 ⋅ K
Next, the Nusselt number, Nu was evaluated for the blood using the following relationship: 1 3 0.407 Nu = 0.069⋅(Gr )Pr E9.6
Where Gr is the Grashof number and Pr is the Prandlt number whose equations are shown below. [33] gβ (T −T )L3 Gr = s inf E9.7 υ 2
cp ⋅ µ Pr = E9.8 K
Using equation E9.5 the convection coefficient for blood was determined to be W approximately hb = 782.3 . It is important to note that blood is not considered to be a m2 ⋅ K Newtonian fluid; however, this approximation can be made because the analysis is considering natural convection; the convection due to the blood is not being forced at high velocities.
9.3 First Order Thermal Model Approximation
As a first order theoretical model a lumped capacitance method was used to approximate a temperature profile the blood may experience as a function of time. A lumped capacitance implies that the temperature gradients are negligible. For this assumption to be valid the Biot number was determined to be approximately 0.23. Capstone 46
h ⋅ L Bi = C E9.9 Kb
The lumped capacitance analysis method is valid for Biot number values less than 0.1, which states that the assumption of a uniform temperature distribution through the blood is reasonable for a transient process. Although the Biot number was determined to be slightly higher than 0.1 it will be used as an approximation to attain a general understanding of the thermal response of the blood bag as a system to optimize the device and testing methods.
The average temperature of the blood can be approximated using equation E9.10.
⎛ hAs ⎞ θ −⎜ ⎟t = e ⎝ ρVc ⎠ E9.10 θi
Where h is the convective coefficient of blood, AsB B is the surface area of the blood bag, ρ is the density of blood, V is the volume, c is the specific heat, θ = T − T∞ , and θi = Ti − T∞ . Solving for the temperature of the blood, ⎛ t ⎞ −⎜ ⎟ ⎜ ⎟ ⎝ RT mcp ⎠ Tb = (Ti −Tinf )⋅e +Tinf E9.11
9.4 Blood Temperature Time Response
The average temperature of the blood was determined by assuming a lumped capacitance method, demonstrated by equation E9.11. [33] The initial blood temperature was assumed to be 0°C, and the ambient temperature was maintained at room temperature, 25°C. The model is used to approximate the temperature at the sensor location based on the effects of the insulative properties incorporated in the device. The ideal case the temperature at the sensor location will read the average temperature of the blood.
The lumped analysis will also indicate how frequently the chip needs to record a measurement based on how quickly the blood will reach 10°C, the maximum storage shipment temperature. Figure 9.3 provides an indication of how fast the blood reaches the maximum storage shipment temperature and the temperature located at the sensor.
Capstone 47
Figure 9.3: Plots the temperature of the blood vs. time.
This plot reveals approximately how fast the blood reaches the ambient room temperature and approximately how fast the blood reaches the maximum storage temperature, and shows how the ambient temperature affects the temperature at the sensor location.
The plot also provides an indication of how frequent the chip needs to take measurements based on how quickly the blood responds to reach 10°C.
9.5 Modeled Temperature Profile
Taking the first order thermal model approximation to be valid an average temperature response was assumed. The initial conditions of the blood contents were assumed to be approximately 37°C, or approximate core body temperature. At time zero the blood bag was placed into a freezer and allowed to cool to the freezer temperature, 0°C, and maintained near 0°C for a period of time.
The ambient temperature profile at time zero was 0°C and maintained at that temperature until the bag was allowed to come to equilibrium with the ambient freezer temperature. The ambient temperature was then spiked to room temperature, approximately 25°C. The spike simulates an operator removing the bag from the freezer to room temperature for a period of 30 minutes. During this time, the blood bag average temperature response is seen to increase, and the sensor temperature was also approximated using equation E9.2.
Capstone 48
Figure 9.4: Theoretical blood and sensor temperature response to ambient temperature spike profile.
Capstone 49
The purpose of this approximation is to gain insight of how the temperature at the sensor location reacts when the ambient temperature is spiked from 0°C to room temperature, 25°C. The spiked portion of the ambient temperature is blown up in Figure 9.5.
Figure 9.5: Blown up section of spiked temperature during a simulated temperature profile. The temperature at the sensor location is slightly high based on the ambient temperature.
The ambient temperature causes the temperature at the sensor location to rise. The difference between the blood temperature and the temperature at the sensor location is approximately -1.5°C or 0.55%. When the temperature suddenly drops back to the freezer temperature, 0°C, the temperature at the sensor location suddenly drops below the blood temperature and the difference between the approximated average blood temperature and the temperature at the sensor location is approximately 0.5°C or less than 0.2% shown in Figures 9.6 and 9.7.
Capstone 50
Figure 9.6: The delta temperature between the approximated blood temperature and the temperature at the sensor location.
Figure 9.7: The % error of the temperature at the sensor location to the approximated blood temperature. Capstone 51
10 Testing
Thermal testing was conducted on the blood bag to verify that the lumped capacitance method is a valid first order approximation although the Biot number is slightly greater than 0.1. Thermal testing was also used to calibrate the Dallas Semiconductor prototype temperature sensor.
10.1 Thermal Testing
10.1.1 Blood Bag Testing
Thermal analysis was conducted on a 600mL blood bag using saline as a working fluid, which has similar properties of blood. The testing on the bag was done to verify that the lumped capacitance is a valid first order approximation to estimate the effects of the thermal resistive properties in each component in the device to determine the temperature at the sensor location.
The objectives of this test is to determine the response of the blood bag contained with saline solution from a steady state 0°C ice bath to room temperature approximately 22-25°C. To determine if large temperature gradients exists within the blood contents as it rests allowing natural convective processes to take place. This data will be used to compare, verify, and modify the theoretical thermal analysis.
A LabView program was designed to collect temperature measurements from 7 different thermocouple sensors. The measurement frequency was set to 5 Hz, thus taking five measurements every second (A measurement every 0.2 seconds). The labview program data was exported to a delimited text file to be plotted using Microsoft Excel.
Figure 10.1: Labview interface for temperature measurements Capstone 52
The seven thermocouples used in the experiment were all inserted into the ice bath, allowed to reach steady state and calibrated using the data acquisition card, so that the proper voltage output correlated to 0°C.
A small incision was made in the side of the blood bag to insert 5 thermocouples. Four surface mount thermocouples were adhered to the inner surface of the blood bag using superglue; two surface mount thermocouples were placed on the front and two were placed on the back sides of the blood bag. The probe was then inserted into the bag to measure the temperature at the center of the blood. Saline solution was inserted into a 600mL blood bag using a syringe Figure 10.2. A vice was used with to clamp of and seal off the incision, Figure 10.3.
A surface mount thermocouple was placed in the ice bath near the blood bag to monitor the ice bath temperature, and a second was placed near the bag in ambient temperature to monitor the room temperature. Figure 10.2: A syringe was used to measure out the appropriate amount of saline solution. The blood bag was completely submerged in the ice bath on its side with the label side facing up. The blood bag was allowed to reach steady state or with all sensor reading 0°C. Once the bag reached steady state the bag was removed from the ice bath and placed sitting upright on the surface of the table. The bag was once again placed on its side with the label side up.
All sensors were allowed to reach at or above 10°C the maximum storage/shipment temperature allowed per the FDA whole blood requirements. This data was then plotted using Excel shown in Figure 10.4.
Figure10.3: Blood bag clamp Capstone 53
Figure 10.4: Blood bag response from 0 degrees Celsius to room temperature
A second test was run with the bag hung vertically in the air. This was done in order to expose all surfaces of the blood bag to determine if the thermal response of the blood increased at a faster rate. The same test procedure was followed, except the bag was removed and hung vertically in the air at room temperature, such that the tubes inserted into the blood bag were pointing upward. The temperature plotted is shown in Figure 10.5.
Figure 10.5: Temperature of hanging bag Capstone 54
10.1.2 Temperature Calibration
To confirm the measurements the prototype devices measure, a thermocouple was taped to the surface of the measurement chip and placed in a refrigerator until a state of equilibrium was reached. Ambient data was collected using a second thermocouple.
The air temperature in the refrigerator fluctuated as a sawtooth-wave function with an amplitude of 3 Celsius degrees and a period of 11 minutes as measured with the free thermocouple. The temperature response at the surface of the chip was similar, with amplitude of 1 Celsius degree. The chip sensed a similar wave of 1 degree cycle every 11 minutes. A sample of a typical response can be seen in Figure 10.6 below.
Board 6 Calibration
5
4
3
2 ] C
e [ 1 r Chip Temp [C] u Surface Temp erat 0 Ambient Temp mp e T
-1
-2
-3
-4 10:19:00 PM 10:26:12 PM 10:33:24 PM 10:40:36 PM 10:47:48 PM 10:55:00 PM Time
Figure 10.6: Sample temperature calibration results
Each measurement device had a certain calibration offset error, but this could easily be adjusted by modifying the download software to calibrate for a particular board’s offset. This could even be automatically saved to the chip user data and used to correct the data at download with no user interference.
There were some deviations from this result, but each is explainable. Not enough data were taken from board 1 to make any determination. Board 2 didn’t quite equalize, but the waves seemed to match in period and amplitude with a slight time offset of approximately 3 minutes. Board 4 sensed a 0.5 degree wave and not a 1 degree wave, but this was due to a resolution error as evident in the number of data points at 2 degrees versus 2.5. Board 7 Capstone 55 sensed a 1.5 degree wave, but this matched the surface thermocouple data. Graphs from each experiment can be found in Appendix E.
10.1.3 Time Calibration
Each prototype was initialized with a 1-minute interval mission and ran for 24 hours at room temperature, and their final time stamp was compared with the elapsed time. No error in time was evident. Future testing should include an examination of time error at other temperatures, as this may affect the frequency of the crystal. The capstone team did not investigate temperature effects on long-term time error due to lack of time in the course.
10.2 Data Logger Testing
A fully constructed data-logger (with urethane and adhesive) was placed on a blood bag filled with saline. The device was brought from room temperature to refrigerator temperature, and back to room temperature over the course of nineteen hours. Using the connector, the data was downloaded and placed in an Excel spreadsheet. The data is plotted in Figure 10.8.
Figure 10.7: Plot of data downloaded from data logger
Capstone 56
This test was performed to verify operation of the data-logger, particularly at low temperatures. As the data shows, the device successfully measured temperature throughout the entire test period.
This testing also shows that the timing of the crystal is not adversely affected by low temperature exposure. It was able to successfully measure data at the correct frequency over the testing period.
10.3 Discussion of Results
The theoretical lumped capacitance was superimposed over the experimental data and determined that the lumped capacitance is a valid response to approximate an average blood temperature response. The fact that the Biot number is not below 0.1 is shown in the beginning of plot in Figure 10.8. When the blood was removed from the ice bath the blood solution was sloshed around in the bag causing the spikes in temperature. However, since the biot number is fairly close to 0.1 these temperature differences smooth out and follow the lumped capacitance model.
Figure 10.8: Thermal Response superimposed with the test data.
The experimental data showed that there was approximately 3.5° temperature difference between the blood that was being insulated by the wood bench and the blood at the surface exposed to the natural convection process. The experimental data in Figure 10.8 shows the two thermocouples exposed to the ambient air read higher temperatures. The thermocouples that were against the wood surface did not reach room temperature as quickly.
Capstone 57
The data shows that based on the actual temperature gradients present in the blood solution that it would be possible for the data-logger to provide a false-positive due to the 3.5° temperature gradient that was measured. Meaning that the data-logger would record that the blood reached its maximum storage temperature when in reality most of the blood may actually be within the storage temperatures. However, the opposite problem may arise if the temperature data-logger was placed face down so that the data-logger would record blood temperatures within the shipment storage range, reading colder temperatures, while the majority of the blood was above the specified temperature range.
The same result was shown when the blood bag was hung vertically in air. It was determined that there was approximately 4.1° temperature difference between the blood at the top of the bag and the blood at the bottom of the bag. This differential most likely arises due to the buoyant forces that arise with warming portions of the blood. As a result it is shown in Figure 10.9 that the thermocouples positioned at the top of the bag measure warmer temperature while the thermocouples at the bottom of the bag measure colder temperatures. The thermocouple probe positioned in the center of the blood bag measures blood temperature between the bottom and top surface mount thermocouples.
Figure 10.9: Theoretical blood temperature response superimposed in the experimental test data.
The theoretical blood bag temperature using a lumped capacitance method was superimposed on the experimental data and it can be shown that the theoretical model depicts fairly closely how the blood temperatures respond with time. The theoretical model approximates closely the temperature measured by the probe at the center of the bag.
Capstone 58
The final testing that was completed was adhering the temperature data-logging device to the label of the blood bag. The blood bag was then placed into a freezer and the temperature recorded at a frequency of 1/60 Hz by the data-logger was compared to the temperature recorded by the thermocouple data, Figure 10.10. It was verified that the temperature at the sensor location was not adversely affected by the ambient temperature.
Figure 10.10: Data logger temperature vs. LabView blood temperature
It was predicted that the temperature sensed by the Dallas Chip would be slightly higher due to the room temperature when removed from the freezer. However, it can be shown after a few minutes the data logger measures the correct temperature of the blood close to the surface, as verified by the thermocouples placed on the inside of the top surface of the blood bag.
This measurement error predicted by the thermal model and verified by experimental data can be used to optimize the component material to isolate it from ambient temperature affects, and calibrate any bias error into the sensor as a result of the component thermal properties. Capstone 59
11 Cost Analysis
A brief cost analysis of the final design was conducted simply to inform McClellan Automation of the cost of components of the system. Assembly labor was not considered, since McClellan has the ability to automate the assembly of the components themselves. Since each customer needs only one or two cable circuits, and since the cable circuitry is made of such inexpensive off-the-shelf components, it was excluded as well. A quantity of 1000 pieces was assumed for an initial production run of sales units. At these quantities the cost per circuit board is $7.10, as shown in Table 11.1.
Table 11.1: Per-board cost analysis Part P/N $ ea Qty/Board Cost Sensor Chip DS1615S $5.0300 1 $5.03 Crystal CM200S $0.4100 1 $0.41 Resistor 1003 $0.0186 1 $0.02 Resistor 1002 $0.0186 1 $0.02 Board Custom $0.4800 1 $0.48 Battery v364 $0.3500 2 $0.70 Batt. Holder 2998 $0.1780 2 $0.36 Adhesive Tape F9473PC $0.0400 1 $0.04 Coating 832B $0.0500 1 $0.05
Cost/board $7.10
Capstone 60
12 Project Results
12.1 Goals Summary
The original goal of the capstone group, to find an application for a flexible temperature sensor circuit and to develop the product, has not been fulfilled. Neither the flexible circuit technology nor the temperature sensing circuit with the accompanying software was finished in time for the capstone team to utilize them in a product. The team was subsequently directed to develop a substitute circuit on standard substrate technology, and to use it in a final temperature sensing prototype for the application they specified. This prototype was developed, and will be used as a sales device by McClellan.
There were several important developments throughout this process that will be useful to McClellan Automation as they develop their flexible circuit. A large, viable market has been found in blood transport and storage. Specifications for the final product to meet the market needs have been made. Concepts of the final design have been created and narrowed to the best fit. Components have been specified for use with the flexible circuit, including a novel power source. A thermal model has been developed and compared to experiments, both to describe the thermal characteristics of a standard blood bag and temperature sensing device.
12.2 Recommendations
Based on the project goals which were summarized in the previous section, there are several improvements for McClellan Automation to make with the second generation of the temperature data-logger.
The most important of these improvements is making the product flexible. This includes several improvements from the first generation prototype completed by the capstone design team. The first of these is the inclusion of the flexible circuit technology developed by Dr. N. Edward Berg. Because of time constraints, Dr. Berg’s circuit was not used in the first generation prototype, but should be included by McClellan Automation in the second generation. This will also include the use of Mylar as a substrate, and using a conductive epoxy to connect the surface-mount components to the circuit board instead of traditional solder. The advantages of using a flexible circuit, are that is will conform to the shape of the blood-bag more easily, and also lower the total device cost because the circuit printing can be done very inexpensively by McClellan Automation.
The other step to making the product flexible is the use of the Loctite two part encapsulant (US5502) described in section 7.3 of this report. Again, due to time constraints, a more common, non-flexible circuit board encapsulant was used in place of the more flexible coating. This was not a problem for the prototype created by the capstone team because the substrate was also non-flexible.
The last step to making the product more flexible would be the use of PowerPaper flexible, printed batteries. The only drawbacks to using these batteries are the cost and development time required. These are both high because PowerPaper is a relatively new technology, Capstone 61 which is in the early stages of development. The use of these batteries, discussed in more detail in section 7.5.3 of this report, is something that can be researched more for later generations as the cost and development time lower.
The other major improvement for the second generation prototype is the inclusion of wireless data transmission. From interviews with professionals at various area hospitals and the Red Cross, it is obvious that ease-of-use is a very important criterion for this device. Wireless download with radio frequency identification (RFID) technology would make data transmission much quicker and easier than the hard connection used with the first generation prototype. The inclusion of RFID would also allow the Red Cross to include the data from the various barcodes currently used in the labels of each bag (See Figure 12.1).
Figure 12.1: Barcodes located on a blood bag label
These barcodes contain the information for expiration date, donor information, and blood type. If RFID were used all of this information could be logged into the computer at the hospital, clinic, or Red Cross facility with one scan instead of multiple scans. It would also take up less space on the blood bag labels than the several bar codes currently used.
The third change that should be made for the second generation design is the use of the circuitry and software designed by Dr. Berg. The circuit designed by Dr. Berg utilizes separate chips for processing, memory, and temperature measurement, unlike the chip used by the capstone team (Dallas Semiconductor DS1615). This change should lower the overall cost of the device, and decrease the size of the circuit. Using separate components will also allow for optimization of the device, specifically the temperature measurement accuracy. In addition, the software designed by Dr. Berg can be optimized to the design specifications for measurement frequency and processing outlined in this report to increase ease of use for the consumer. Capstone 62
13 References
[1] “All about blood”. Advanced transfusion and cellular therapies worldwide . September 25, 2005. < http://www.aabb.org/All_About_Blood/FAQs/aabb_faqs.htm#1>.
[2] Fleming-Michael, Karen. “THE ULTIMATE SHIRT: Army Invents Wearable Medic”. Soldier Tech., Military.Com.
[3] Mundt, Carsten. LifeGuard—A Wearable Monitoring System. NASA Ames Astrobionics. February, 2, 2004. Accessed: July 2005.
[4] Dunbar, Brian; “LifeGuard: Wireless Phsiological Monitor”; Dino, Jonas, ed., NASA Ames Research Center;
[5] Dorsey, Michael W., “On the Front Lines of Telemedicine.” September 2, 2004.
[6] Krulevitch, Peter A., Maghribi, Mariam N., Benett, William J., Hamilton, Julie K., Rose, Klint A., Davidson, James Courney, Strauch, Mark S. Electrical Unit Integrated into a Flexible Polymer Body. The Regents of the University of California, assignee, Patent 6,878,643. 12 Apr. 2005.
[7] “Raynaud’s Phenomenon Topic Overview”. WebMD Health. August 1, 2005.
[8] “Circulatory Problem’s Causes and Treatments”. WebMD Health. August 1, 2005.
[9] “Trying to Conceive: Fertility Charting 101”. WebMD Health. August 1, 2005.
[10] “MicroMini-Motionlogger and Family of Sensors”. Ambulatory Monitoring, Inc. August 1, 2005.
[11] “SenseWear Pro2 Armband”. BodyMedia. August 1, 2005.
[12] Stivoric, John, Gemperle, Francine, Kasabach, Christopher. Wearable Human Physiological Data Sensors and Reporting System Therefor. BodyMedia, Inc., assignee. Patent 6,527,711. 4. Mar. 2003.
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[13] Kumar, Harpal, Johnson, Paul, Llewellyn, Michael, Mullarkey, William, New, William, Nicolson, Laurence, O’Brien, William, Place, John, Relph, Peter. Portable Remote Patient Telemonitoring System. Nexan Limited, assignee. Patent 6,416,471. 9 Jul. 2002.
[14] Ferguson, Pete, Kumar, Harpal, Lay, Graham, Llewellyn, Mike, Place, John. . Portable Remote Patient Telemonitoring System Using a Memory Card or Smart Card. Nexan Limited, assignee. Patent 6,454,708. 24 Sep. 2002
[15] Ouchi, Kazushige, Suzuki, Takuji, and Doi, Miwako. “LifeMinder: A Wearable Healthcare Support System with Timely Instruction Based on the User’s Context.” IEICE Trans. Inf & Syst. Vol E87-D (2004): 1361-1368.
[16] “PDAs.” Best Buy. August 1, 2005.
[17] Wigley, Fredrick, Wise, Robert, Schwartz, Paul, Lew, Ark, Scott, David, Le, Binh. Ambulatory Surface Skin Temperature Monitor. Johns Hopkins University, assignee. Patent 6,487,913. 25 Jan. 2005.
[18] “Clean Beyond the White Glove Test”. Medical Design Magazine. July/August 2001.
[19] Food and Drug Administration, Center for Drugs and Biologics and Center for Devices and Radiological Health. “Control of Micorobiological Contamination.” Current Good Manufacturing Processes 21 CFR Section 211.113(b). Internet webpage maintained by Kamm & Associates:
[20] Global Engineering Documents, IHS Global. Internet search engine:
[21] Donley, Kelli M. “Sterilization Indicators Shine Light on Equipment, Human Errors.” Infection Control Today, December 2001.
[22] Bolea, Phillip A., Kippenhan, Roland C., Kirckof, Steven S., and Rumble, Richard M. Electronic System for Tracking and Monitoring Articles to be Sterilized and Associated Method. 3M Innovative Properties Company, assignee. Patent 6,485,979. 26 Nov. 2002
[23] “Products” KSW-Microtec. August , 2005.
[24] “Acti-tag Temperature”. Technopuce. August 1.
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[25] “Ibuttons”. Dallas Semiconductor. August 1.
[26] “SL 150 Series”. Signatrol Data Logging Solutions. August 1
[27] “Title 21—Food and Drugs,” Chapter 1—Food and Drug Administration, Department of Health and Human Services, sections 600-799, website: http://www.access.gpo.gov/nara/cfr/waisidx_05/21cfrv7_05.html
[28] Ulrich, Karl, T.; Eppinger, Steven D. Product Design and Development. Third Edition, McGraw-Hill/Irwin. 2003.
[29] Biosynergy, Inc. “Blood Bank/Surgery.” website:
[30] “How does dry ice work?”. How Stuff Works. October 1, 2005. http://science.howstuffworks.com/question264.htm.
[31] “HYSOL US5502 Formerly Loctite 821156R/C Liquid Urethane Encapsulant”. Loctite. August, 2001.
[32] “VHB Adhesive Transfer Tapes with Adhesive 100MP”. 3M. April, 2005.
[33] “3M VHB Tape Cold Temperature Performance”. 3M. March, 1998.
[33] Incropera, Frank, P., DeWitt, David, P. Introduction to Heat Transfer. Fourth Edition. John Wiley & Sons, Inc. C 2002, pp. 4-11; 88-101; 507-520.
[34] “Computer Assisted Design of Thermal System.” Human Blood Properties. September 23, 2005. website: San Diego Plastics, Inc. http://www.sdplastics.com/pvc.html. Last Activated October 31, 2005.
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Appendix A: Thermal Calculations Capstone 66
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Appendix B: Final Circuit Subcomponents
Cable Components Ref. Vendor VP/N MP/N Spec Mount .01 uF Ceramic C1, C2 Digi-Key BC1111CT-ND K103K15X7RH5TL2 Capacitor Board .33 uF Ceramic C3, C4 Digi-Key 399-2054-ND C322C334M5U5CA Capacitor Board .1 uF Ceramic C5 Digi-Key 399-2174-ND C320C104K5R5CA Capacitor Board 22 uF Tantalum C6 Digi-Key 399-1318-ND T356E226K010AS Capacitor Board D1 Digi-Key P316-ND LN324GP Green LED Board D2 Digi-Key P315-ND LN224RP Red LED Board D3 Digi-Key 1N4001DICT-ND 1N4001-T Standard Diode Board J1 Digi-Key 61E09F-ND 172-E09-202-001 Connector Cable R2, R1 Digi-Key 1.0KH-ND CFR-50JB-1K0 1K Resistor Board S1 Carling Unk 3SSIP67 Switch Cable R6 Radioshack CFR-50JB-150K 150KH-ND 150 Resistor Board 10K R7 Radioshack 271-282 Unk Potentiometer Board 5V Voltage U3 Digi-Key 276-1778 LM317T Regulator Board RS-232 U1 Newark 52F8899 DS275 Transciever Board
Board Mount Breadboard Prototype Components R3 Digi-Key 10KH-ND CFR-50JB-10K 10K Resistor Board R5 Digi-Key 100KH-ND CFR-50JB-100K 100K Resistor Board Temperature U2 Newark 90B7735 DS1615 Recorder IC Board 32.768 kHz, 6pF X1 Digi-Key 300-1000-ND CFS-206 Crystal Board
Final Prototype Components Ref. Vendor VP/N MP/N Spec Mount D4 Newark 06WX2723 V364 3.6V Battery Surface D4a McMaster 7604K13 2998 Battery Holder Surface R3 Digi-Key 311-10.0KFCT-ND 9C12063A1002FKHFT 10K Resistor Surface R5 Digi-Key 311-100KFCT-ND 9C12063A1003FKHFT 100K Resistor Surface Temperature U2 Newark 74C2163 DS1615S Recorder IC Surface 32.768 kHz, 6pF X1 Digi-Key 300-2034-1-ND CM200S Crystal Surface
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Appendix C: Final Prototype Circuit
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Appendix D: Final Cable Circuit
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Appendix E: Temperature Calibration Test Results ] p p m m [C e e p T m T t en i Te ace f b ip r h C Su Am 7 AM 1 : 51 : 2 4 AM 2 : 8 4 2: n 1 AM atio 3 r : 45 : 2 Calib 1 d M e ar A m Ti 38 Bo : 2 4 2: 6 AM 4 : 9 3 2: M A 53 : 6 3 2: 0 AM 0 : 4 5 4 3 2 1 0 -1 -2 -3 3
2:
] C [ e r u erat p m e T
Capstone 82 ] p p [C m m
e e p T m t e e T c en T a bi p i rf h m C Su A 48 : 5 AM 1 4: 36 : 8 AM 0 4: 24 : 1 AM 0 4: n 12 : 4 AM atio 5 r 3: 00 : 2 Calib 7 AM 4 d e 3: ar m Ti Bo 48 : 9 AM 3 3: 36 : 2 AM 3 3: 24 : 5 AM 2 3: 12 : 8 AM 1 3: 00 : 1 AM 1
9 8 7 6 5 4 3 2 1 0
3: 10
] C [ e r u erat mp e T
Capstone 83 ] p p [C m m
e e p T m t e e T c en T a bi p i rf h m C Su A 6 3 7: 4 AM : 12 4 2 : 0 4 AM 12: 2 1 3: 3 AM : n 12 atio 0 r 0 6: 2 AM : 12 4 Calib d e 8 ar 4 m Ti 18: Bo AM : 12 6 3 1: 1 AM : 12 24 : 4 0 AM : 12 2 1 57: PM : 11 0 0 : 0 5 PM
5 4 3 2 1 0
-1 -2 -3 11:
] C [ e r u at r e mp e T
Capstone 84 ] p p [C m m
e e p T m t e e T c en T a bi p i rf h m C Su A 6 3 : 2 4 AM 12: 4 2 35: AM : 12 2 1 8: 2 AM : n 12 atio r 0 0 21: AM : 12 5 Calib d e ar 8 m 4 Ti 3: Bo 1 AM : 12 6 3 6: 0 AM : 12 4 2 : 9 5 PM 11: 2 1 2: 5 PM : 11 0 0 : 5 4 PM
5 4 3 2 1 0
-1 -2 -3 11:
] C [ e r u at r e mp e T
Capstone 85 ] p p [C m m
e e p T m t e e T c en T a bi p i rf h m C Su A M 00 P : 5 5 : 0 1 M P 8 4 47: : 10 n atio r M P 6 3 6 Calib 40: : d e 10 ar m Ti Bo M P 4 2 : 3 3 10: M P 2 1 : 6 2 10: M 00 P : 9 5 4 3 2 1 0 1 -1 -2 -3 -4 :
0
1
] C [ e r u at r e mp e T
Capstone 86 ] p p m m [C e e p T m T t en i Te ace f b ip r h C Su Am M P 12 : 5 5 : 10 M P 00 : 8 4 : 0 1 M n P 48 : atio 0 r 4 : 0 1 Calib M P 7 6 d 3 e ar m 33: : Ti Bo 10 M 24 P : 6 2 : 10 M 12 P : 9 1 : 10 M P 0 0 2: 1 : 0 1 M P 8 4 4: 5 4 3 2 1 0 0 -1 -2 -3 -4 :
0
1
] C [ e r u at er mp e T