Solid State Sensors Glossary of Terms

Absolute Maximum Ratings Current sourcing output (PNP) — Load IAQ — Indoor Air Quality: calculated

Supply Voltage: Range of voltage is connected between sensor and using CO2 levels found in indoor air; high

which may be applied to the positive ground. Current flows from the sensor levels of CO2 create an awareness of terminal of a sensor without damage. through the load to ground (open emit- volatile organic compounds (VOCs) and Voltage Externally Applied to Output: ter). bacteria. Refers to the breakdown voltage of the output transistor between the collector Dew Point — Point at which a given sam- Ice Point — Equal to 0°C (32°F), is the and emitter when transistor is OFF. Volt- ple of air is saturated. Related standards temperature at which pure water at 1 atm age measured at the output terminals of measurement include Frost Point, and of pressure freezes. It is the physical phe- of an inactivated sensor must never Ice Point. nomenon upon which the centigrade exceed 30 VDC, or sensor may be temperature scale was originally based: damaged. Differential travel (D.T.) — Plunger or 0°C ⍧ pure water, at 1 atm pressure, Output Current: Maximum output cur- actuator travel from point where contacts freezes rent which may flow through an actuated ‘‘snap-over’’ to point where they ‘‘snap- 100°C ⍧ pure water, at 1 atm pres- sensor without damaging the sensor. back.’’ sure, boils. Temperature: Range over which the sensor will operate without damage. Enthalpy — A thermodynamic function of Linearity — The closeness of an actual This is not the actual rated temperature a system, equivalent to the sum of the curve to a specified straightline. The de- range over which the sensor will meet internal energy of the system plus the gree to which the output of a linear device the specified operational characteris- product of its volume multiplied by the deviates from ideal performance. tics. pressure exerted on it by its surround- Magnetic Flux: Hall effect sensors can- ings. Linear output — An output which chang- not be damaged by excessively large es in proportion to the input. magnetic field density. Flux concentrator — Any ferrous materi- al positioned so as to concentrate mag- Magnetoresistive effect — The change Bipolar sensor, magnetic — A Hall effect netic flux in the sensing area, thereby in the resistance of a semiconductor de- sensor that has a plus (South pole) maxi- increasing the flux density as seen by the vice in which the electrical resistance is a mum operate point, and a minus (North Hall effect sensor. function of the applied magnetic field. A pole) minimum release point. Operate magnetoresistive element will respond to and release points can also be both posi- Frost Point — If measurements are made any magnetic fields (North or South pole) tive or both negative. Therefore, latching below freezing point of water (if indicated which are parallel to it. cannot be guaranteed. Ring magnets dew point is below freezing point of wa- are usually used with bipolar sensors. ter), then equilibrium occurs at vapor Moisture Measurements — Mix of ra- pressure of ice (not water). Vapor pres- tios, volume percent, and specific humid- Bipolar-latching sensor, magnetic —A sure of ice is less than that of water. The ity – used when water vapor is an impurity true latching device. Guaranteed to frost point is slightly higher than dew or a defined component of a process gas switch on with positive gauss only and point. Often used when dryness of the mixture used in manufacturing. switch off with negative gauss only. gas is an important determination. North pole (magnetic) — The pole that is Capillary Tube Flow Design — Exam- Gauss — The CGS unit of flux density attracted to the geographical north pole, ines differences in two self-heated RTDs (magnetic induction). therby repelling the north seeking pole of held at equal temperature or equal input. a compass. Lines of flux are directed Hall effect — The description given to the away from this pole. Current sinking output (NPN) — Load is following phenomena: When a conductor connected between power supply and through which a current is flowing is Omnipolar sensor, magnetic – A sensor sensor. Current flows from the load placed in a magnetic field, a difference in that operates with any magnetic field through the sensor to ground (open potential (Hall voltage) is generated be- (North or South pole). collector). tween the two opposed edges of the conductor in the direction perpendicular to Operating force (O.F.) — Amount of both the field and the current. force applied to switch plunger or actua-

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tor to cause contact ‘‘snap-over.’’ Note in Reference/Index Hysteresis — The property of a digital the case of adjustable actuators, the force Hall effect sensor where its operate point is measured from the maximum length is different in value from its release point. position of the lever.

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Operating position (O.P.) — Position of Rated Electrical Characteristics Regulated Voltage — Desired output switch plunger or actuator at which point Supply Voltage: Range of voltage over voltage is maintained regardless of nor- contacts snap from normal to operated which the sensor is guaranteed to oper- mal change to input or output load. position. Note that in the case of flexible or ate within performance specifications. adjustable actuators, the operating posi- Supply Current: Corresponds to cur- South pole (magnetic) — The pole that tion is measured from the end of the lever rent drain on the Vs terminal. Supply is repelled by the geographical north or its maximum length. Location of oper- current is dependent upon the supply pole, and therefore attracts the north ating position measurement shown on voltage. seeking pole of a compass. Lines of flux mounting dimension drawings. Output Voltage: Saturation voltage are directed toward this pole. (VSAT) of the output transistor. Voltage Overtravel (O.T.) — Plunger or actuator which appears at the output due to in- Temperature calibrations — Single travel safely available beyond operating herent voltage drop of the output transis- Point: calibration at 0°C (Ice Point); Two position. tor in the ON condition. Point: calibration at 0°C and100°C; Three Output Current: Maximum output cur- Point: calibration at 0°C, 100°C, and Pretravel (P.T.) — Distance or angle trav- rent at which the sensor is guaranteed to 250°C. eled in moving plunger or actuator from operate within performance specifica- free position to operating position. tions. Thermodynamic Temperature Scale — Output Leakage Current: Maximum Varies slightly from Fahrenheit: 211.95° Psychrometrics — The study of water current which remains flowing through vs. 212°F. vapor concentration in air as a function of the output transistor when it is turned temperature and pressure. This field of OFF. Unipolar sensor, magnetic — A Hall ef- study includes numerous moisture terms Output Switching Time: Time required fect sensor that has a plus maximum op- and units. by the output transistor to change from erate point, and a plus minimum release one logic state to the other after a point. One magnetic pole (South) is re- Rankine Scale — A scale of absolute change has been initiated. This specifi- quired to operate and release a unipolar temperature using Fahrenheit degrees, in cation applies only to conditions spec- sensor. which the freezing point of water is ified on the product drawing. 491.69° and the boiling point of water is VOCs-Volatile Organic Compounds — 671.69°, measure of thermodynamic tem- Ratiometric — The output voltage is pro- bioeffluents (bacterial and organic com- perature. portional to the supply voltage in some pounds) found in indoor air as CO2 levels

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