Equivalent Resistance

Total Page：16

File Type：pdf, Size：1020Kb

Equivalent Resistance Consider a circuit connected to a current source and a voltmeter as shown in Figure 1. The input to this circuit is the current of the current source and the output is the voltage measured by the voltmeter. Figure 1 Measuring the equivalent resistance of Circuit R. When “Circuit R” consists entirely of resistors, the output of this circuit is proportional to the input. Let’s denote the constant of proportionality as Req. Then VRIoeq= i (1) This is the same equation that we would get by applying Ohm’s law in Figure 2. Figure 2 Interpreting the equivalent circuit. Apparently Circuit R in Figure 1 acts like the single resistor Req in Figure 2. (This observation explains our choice of Req as the name of the constant of proportionality in Equation 1.) The constant Req is called “the equivalent resistance of circuit R as seen looking into the terminals a- b”. This is frequently shortened to “the equivalent resistance of Circuit R” or “the resistance seen looking into a-b”. In some contexts, Req is called the input resistance, the output resistance or the Thevenin resistance (more on this later). Figure 3a illustrates a notation that is sometimes used to indicate Req. This notion indicates that Circuit R is equivalent to a single resistor as shown in Figure 3b. Figure 3 (a) A notion indicating the equivalent resistance and (b) the interpretation of that notation. Figure 1 shows how to calculate or measure the equivalent resistance. We apply a current input, Ii, measure the resulting voltage Vo, and calculate Vo Req = (1) Ii The equivalent resistance can also be measured using and ohmmeter as shown in Figure 4. The color-coding of the ohmmeter probes can be ignored. (A multimeter is a meter that can be used to measure voltages, currents or resistances. A dial on the front of the multimeter is used to select which quantity will be measured. A voltmeter may well be a multimeter set to measure voltage. The color-coded probes of the multimeter will then indicate the reference polarity of the measured voltage. A multimeter that is set to measure resistance is an ohmmeter. The probes will still be color-coded, but now the color-coding has no significance.) Figure 4 Measuring equivalent resistance using an ohmmeter. .

Copy Link

Recommended publications

1806-A Electronic Voltmeter, Manual
OPERATING INSTRUCTIONS TYPE 1806-A ELECTRONIC VOLTMETER Form 1806-0100-C March, 1967 Copyright 1963 General Radio Company West Concord, Massachusetts, USA GENERAL RADIO COMPANY WEST CONCORD, MASSACHUSETTS, USA SPECIFICATIONS DC VO~TMETER Voltage Ro.nge: Four ranges, 1.5, 15, 150, and 1500 V, full scale, positive or negative. Minimum reading is 0.005 V. Input Resistance: 100 M!'l, ±5%; also "open grid" on all but the 1500-V range. Grid current is less than I0-10 A. Accuracy: ±2% of indicated value from one-tenth of full scale to full scale; ±0.2% of full scale from one-tenth of full scale to zero. Scale is logarithmic from one-tenth of full scale to full scale, permitting constant-percentage readability over that range. AC VOLTMETER Voltage Range: Four ranges, 1.5, 15, 150, and 1500 V, full scale. Minimum reading on most sensitive range is 0.1 V. Input Impedance: Probe, approximately 25 Mn in parallel with 2 pF; with TYPE 1806-P2 Range Multiplier, 2500 M!'l in parallel with 2 pF; at binding post on panel, 25 Mn in parallel with 30 pF. Accuracy: At 400 c/ s, ±2% of indicated value from 1.5 V to 1500 V; ±3% of indicated value from 0.1 V to 1.5 V. Waveform Error: On the higher ac-voltage ranges, the instrument operates as a peak voltmeter, calibrated to read rms values of a sine wave or 0.707 of the peak value of a complex wave. On distorted waveforms the percentage deviation of the reading from the rms value may be as large as the percentage of harmonics present.
[Show full text]
The Accuracy Comparison of Oscilloscope and Voltmeter Utilizated in Getting Dielectric Constant Values
Proceeding The 1st IBSC: Towards The Extended Use Of Basic Science For Enhancing Health, Environment, Energy And Biotechnology 211 ISBN: 978-602-60569-5-5 The Accuracy Comparison of Oscilloscope and Voltmeter Utilizated in Getting Dielectric Constant Values Bowo Eko Cahyono1, Misto1, Rofiatun1 1 Physics Departement of MIPA Faculty, Jember University, Jember – Indonesia, e-mail: [email protected] Abstract— Parallel plate capacitor is widely used as a sensor for many purposes. Researches which have used parallel plate capacitor were investigation of dielectric properties of soil in various temperature [1], characterization if cement’s dielectric [2], and measuring the dielectric constant of material in various thickness [3]. In the investigation the changing of dielectric constant, indirect method can be applied to get the dielectric constant number by measuring the voltage of input and output of the utilized circuit [4]. Oscilloscope is able to measure the voltage value although the common tool for that measurement is voltmeter. This research aims to investigate the accuracy of voltage measurement by using oscilloscope and voltmeter which leads to the accuracy of values of dielectric constant. The experiment is carried out by an electric circuit consisting of ceramic capacitor and sensor of parallel plate capacitor, function generator as a current source, oscilloscope, and voltmeters. Sensor of parallel plate capacitor is filled up with cooking oil in various concentrations, and the output voltage of the circuit is measured by using oscilloscope and also voltmeter as well. The resulted voltage values are then applied to the equation to get dielectric constant values. Finally the plot is made for dielectric constant values along the changing of cooking oil concentration.
[Show full text]
Part 2 - Condenser Testers and Testing Correctly Part1 Condenser Testers and Testing Correctly.Doc Rev
Part 2 - Condenser Testers and Testing Correctly Part1_Condenser_Testers_And_Testing_Correctly.doc Rev. 2.0 W. Mohat 16/04/2020 By: Bill Mohat / AOMCI Western Reserve Chapter If you have read Part 1 of this Technical Series on Condensers, you will know that the overwhelming majority of your condenser failures are due to breakdown of the insulating plastic film insulating layers inside the condenser. This allows the high voltages created by the “arcing” across your breaker points to jump through holes in the insulating film, causing your ignition system to short out. These failures, unfortunately, only happen at high voltages (often 200 to 500Volts AC)….which means that the majority of “capacitor testers" and "capacitor test techniques" will NOT find this failure mode, which is the MAJORITY of the condenser failure you are likely to encounter. Bottom line is, to test a condenser COMPLETELY, you must test it in three stages: 1) Check with a ohmmeter, or a capacitance meter, to see if the condenser is shorted or not. 2) Assuming your condenser is not shorted, use a capacitance meter to make sure it has the expected VALUE of capacitance that your motor needs. 3) Assuming you pass these first two step2, you then need to test your condenser on piece of test equipment that SPECIFICALLY tests for insulation breakdown under high voltages. (As mentioned earlier, you ohmmeter and capacitance meter only put about one volt across a capacitor when testing it. You need to put perhaps 300 or 400 times that amount of voltage across the condenser, to see if it’s insulation has failed, allowing electricity to “arc across" between the metal plates when under high voltage stress.
[Show full text]
Voltage and Power Measurements Fundamentals, Definitions, Products 60 Years of Competence in Voltage and Power Measurements
Voltage and Power Measurements Fundamentals, Definitions, Products 60 Years of Competence in Voltage and Power Measurements RF measurements go hand in hand with the name of Rohde & Schwarz. This company was one of the founders of this discipline in the thirties and has ever since been strongly influencing it. Voltmeters and power meters have been an integral part of the company‘s product line right from the very early days and are setting stand- ards worldwide to this day. Rohde & Schwarz produces voltmeters and power meters for all relevant fre- quency bands and power classes cov- ering a wide range of applications. This brochure presents the current line of products and explains associated fundamentals and definitions. WF 40802-2 Contents RF Voltage and Power Measurements using Rohde & Schwarz Instruments 3 RF Millivoltmeters 6 Terminating Power Meters 7 Power Sensors for URV/NRV Family 8 Voltage Sensors for URV/NRV Family 9 Directional Power Meters 10 RMS/Peak Voltmeters 11 Application: PEP Measurement 12 Peak Power Sensors for Digital Mobile Radio 13 Fundamentals of RF Power Measurement 14 Definitions of Voltage and Power Measurements 34 References 38 2 Voltage and Power Measurements RF Voltage and Power Measurements The main quality characteristics of a parison with another instrument is The frequency range extends from DC voltmeter or power meter are high hampered by the effect of mismatch. to 40 GHz. Several sensors with differ- measurement accuracy and short Rohde & Schwarz resorts to a series of ent frequency and power ratings are measurement time. Both can be measures to ensure that the user can required to cover the entire measure- achieved through utmost care in the fully rely on the voltmeters and power ment range.
[Show full text]
(Ohmmeter). Aims: • Calibrating of a Sensitive Galvanometer for Measuring a Resistance
Exp ( ) Calibrating of a sensitive galvanometer for measuring a resistance (Ohmmeter). Aims: • Calibrating of a sensitive galvanometer for measuring a resistance. The theory When a galvanometer is used as an ohmmeter for measuring an ohmic resistance R, the deviation angle θ of the galvanometer’s coil is directly proportional to the flowing current through the coil and inversely proportional to the value of the resistance. The deviation will reach to the maximum end when the resistance equals to zero or the current has the maximum value. For this reason, the scale will be divide by inversely way in comparison with the ammeter and the voltmeter. The original circuit as shown in Fig(1) consists of a dry cell(E) , rheostat and ammeter (A) are connected in series with small resistor s has the range of 1 omega. The two terminals of “s” are connected in parallel to another combination includes a sensitive galvanometer “G” which has internal resistance “r” and a resistors box “R”, this combination is called the measuring circuit. When the value of R equals zero, and by moving the rheostat in the original circuit, it is possible to set the flowing electric current in measuring the circuit as a maximum value od deviation in the galvanometer. By assigning different values of R, the deviation θ is decreasing with increasing the value of R or by another meaning when the flowing current through the galvanometer decreases. Therefore, the current through the galvanometer is inversely proportional to the value of R according the following Figure 1: Ohmmeter Circuit diagram equation; V=I(R+r) R=V/I-r or R=V/θ-r 1 | P a g e This is a straight-line equation between R and (1/θ) as shown in Fig(2).
[Show full text]
Massachusetts Institute of Technology Department of Electrical Engineering and Computer Science
Massachusetts Institute of Technology Department of Electrical Engineering and Computer Science 6.002 - Circuits and Electronics Fall 2004 Lab Equipment Handout (Handout F04-009) Prepared by Iahn Cajigas González (EECS '02) Updated by Ben Walker (EECS ’03) in September, 2003 This handout is intended to provide a brief technical overview of the lab instruments which we will be using in 6.002: the oscilloscope, multimeter, function generator, and the protoboard. It incorporates much of the material found in the individual instrument manuals, while including some background information as to how each of the instruments work. The goal of this handout is to serve as a reference of common lab procedures and terminology, while trying to build technical intuition about each instrument's functionality and familiarizing students with their use. Students with previous lab experience might find it helpful to simply skim over the handout and focus only on unfamiliar sections and terminology. THE OSCILLOSCOPE The oscilloscope is an electronic instrument based on the cathode ray tube (CRT) – not unlike the picture tube of a television set – which is capable of generating a graph of an input signal versus a second variable. In most applications the vertical (Y) axis represents voltage and the horizontal (X) axis represents time (although other configurations are possible). Essentially, the oscilloscope consists of four main parts: an electron gun, a time-base generator (that serves as a clock), two sets of deflection plates used to steer the electron beam, and a phosphorescent screen which lights up when struck by electrons. The electron gun, deflection plates, and the phosphorescent screen are all enclosed by a glass envelope which has been sealed and evacuated.
[Show full text]
Using Multimeters
ORESU-G1-77-005 C. 3 Usingmultimeters lVlarine electrorocs boats gPIII I,,",.", I,'59< ~4'pg,g!gg By EdwardKolbe DC voltmeter CommercialFisheries Engineer, OSU Marine ScienceCenter, Newport Most multirnetersare designedfor measuringboth DC and AC voltages. AssistantProfessor of Agricultural Engineering This bulletin concentrates on how to Oregon State University measureDC voltages;procedures for making AC measurementsare similar. First, plug one of the leadsinto the Multimeters measure electrical voltage, negativeterminal, properly called a resistance,and current, For wiring and jack, marked ! or "COM" for troubleshootingon boats,they can be common! . Standard electrical practice extremelyuseful. Applications include: usesthe black wire for the ground, checkingthe continuity of wiring which is usuallythe negativeterminal. locating breaksin opencircuits; testing The other lead usually red, to signify fusesand diodes;measuring battery the "hot" sideof the circuit! goesinto voltageand voltagedrop over wires and the positivejack, marked + !. After eIectricalloads; identifying "hot" and selectingthe proper DC voltagerange groundedwires; locatingshort circuitsor with the selector switch, measure DC smallcurrent leaks;and checking voltageby touchingthe -! lead to the alternator and generator output, negativeterminal or wire and the + ! A multimeter, also called a volt-ohm- lead to the positiveterminaI or wire. milliammeter VOM!, is actually three Selectingthe proper voltagerange is toob in one.It is a voltmetercapable of important. It is achieved
[Show full text]
Electronic Voltmeters and Ammeters - Alessandro Ferrero, Halit Eren
ELECTRICAL ENGINEERING – Vol. II - Electronic Voltmeters and Ammeters - Alessandro Ferrero, Halit Eren ELECTRONIC VOLTMETERS AND AMMETERS Alessandro Ferrero Dipartimento di Elettrotecnica, Politecnico di Milano, Italy Halit Eren Curtin University of Technology, Perth, Western Australia Keywords: currents, voltages, measurements, standards, analog voltmeters, digital voltmeters, microvoltmeters, oscilloscopes Contents 1. Introduction. 2. Analog Meters 2.1. DC Analog Voltmeters and Ammeters 2.2. AC Analog Voltmeters and Ammeters 2.3. True rms Analog Voltmeters 3. Digital Meters 3.1. Dual-Slope DVMs 3.2. Successive-Approximation ADCs 3.3. AC Digital Voltmeters and Ammeters 3.4. Frequency Response of AC Meters 4. Radio-Frequency Microvoltmeters 5. Vacuum-Tube Voltmeters and Oscilloscopes 5.1. Analog Oscilloscopes 5.2. Digital Storage Oscilloscopes (DSOs) 5.3. Portable Oscilloscopes 5.4. High-Voltage Oscilloscopes Appendix Glossary Bibliography Biographical Sketches Summary Voltage UNESCOand current measurements are – esse EOLSSntial parts of engineering and science. Instruments that measure voltages and currents are called voltmeters and ammeters, respectively. ThereSAMPLE are two distinct types of voltmeterCHAPTERS and ammeter, which differ from each other by the operating principle that they are based on: electromechanical instruments and electronic instruments, which also include oscilloscopes. Electromechanical voltmeters and ammeters, including thermal-type instruments, represent early technology, but still are used in many applications. Basic elements of voltages and currents from the basic physical principles have been introduced in the electromechanical voltage and current measurements section. Also, voltage and currents standards have been dealt with in detail in other articles. ©Encyclopedia of Life Support Systems (EOLSS) ELECTRICAL ENGINEERING – Vol. II - Electronic Voltmeters and Ammeters - Alessandro Ferrero, Halit Eren In this article, modern electronic voltmeters and ammeters are discussed.
[Show full text]
TI S4 Audio Frequency Test Apparatus.Pdf
TECHNICAL INSTRUCTION S.4 Audio-frequency Test Apparatus BRITISH BROADCASTING , CORPORATION ENGINEERING DlVlSlON - ', : . iv- TECHNICAL INSTRUCTION S.4 Third Issue 1966 instruction S.4 Page reissued May. 1966 CONTENTS Page Section I . Amplifier Detector AD14 . 1.1 Section 2 . Variable Attenuator AT119 . Section 3 . Wheatstone Bridge BG/I . Section 4 . Calibration IJnit CALI1 . Section 5. Harmonic Routine Tester FHP/3 . Section 6 . 0.B. Testing Unit 0BT/2 . Section . 7 . Fixed-frequency Oscillators OS/9. OS/ 10. OS/ IOA . Section 8 . Variable-frequency Oscillators TS/5 .. TS/7 . 1' . TS/8 . TS/9 . TS/ 10. TS/ 1OP . Section 9 . Portable Oscillators PTS/9 . PTS/IO . ... PTS/12 . PTS/13 . PTS/l5 .... PTS/l6 .... Appendix . The Zero Phase-shift Oscillator with Wien-bridge Control Section 10. Transmission Measuring Set TM/I . Section 1 I . Peak Programme Meter Amplifiers PPM/2 ..... PPM/6 . TPM/3 . Section 12 Valve Test Panels VT/4. VT/5 "d . Section 13. Microphone Cable Tester MCT/I . Section 14 . Aural Sensitivity Networks ASN/3. ASN/4 Section 15 . Portable Amplifier Detector PAD19 . Section 16. Portable Intermodulation Tester PIT11 Section 17. A.C. Test Meters ATM/I. ATM/IP . Section 18 . Routine Line Testers RLT/I. RLT/IP . Section 19. Standard Level Panel SLP/3 . Section 20 . A.C. Test Bay AC/55 . Section 21 . Fixed-frequency Oscillators: OS2 Series Standard Level Meter ME1611 . INSTRUCTION S.4 Page reissued May 1966 ... CIRCUIT DIAGRAMS AT END Fig. 1. Amplifier Detector AD14 Fig. 2. Wheatstone Bridge BG/1 Fig. 3. Harmonic Routine Tester FHP/3 Fig. 4. Oscillator OS/9 Fig.
[Show full text]
A History of Impedance Measurements
A History of Impedance Measurements by Henry P. Hall Preface 2 Scope 2 Acknowledgements 2 Part I. The Early Experimenters 1775-1915 3 1.1 Earliest Measurements, Dc Resistance 3 1.2 Dc to Ac, Capacitance and Inductance Measurements 6 1.3 An Abundance of Bridges 10 References, Part I 14 Part II. The First Commercial Instruments 1900-1945 16 2.1 Comment: Putting it All Together 16 2.2 Early Dc Bridges 16 2.3 Other Early Dc Instruments 20 2.4 Early Ac Bridges 21 2.5 Other Early Ac Instruments 25 References Part II 26 Part III. Electronics Comes of Age 1946-1965 28 3.1 Comment: The Post-War Boom 28 3.2 General Purpose, “RLC” or “Universal” Bridges 28 3.3 Dc Bridges 30 3.4 Precision Ac Bridges: The Transformer Ratio-Arm Bridge 32 3.5 RF Bridges 37 3.6 Special Purpose Bridges 38 3,7 Impedance Meters 39 3.8 Impedance Comparators 40 3.9 Electronics in Instruments 42 References Part III 44 Part IV. The Digital Era 1966-Present 47 4.1 Comment: Measurements in the Digital Age 47 4.2 Digital Dc Meters 47 4.3 Ac Digital Meters 48 4.4 Automatic Ac Bridges 50 4.5 Computer-Bridge Systems 52 4.6 Computers in Meters and Bridges 52 4.7 Computing Impedance Meters 53 4.8 Instruments in Use Today 55 4.9 A Long Way from Ohm 57 References Part IV 59 Appendices: A. A Transformer Equivalent Circuit 60 B. LRC or Universal Bridges 61 C. Microprocessor-Base Impedance Meters 62 A HISTORY OF IMPEDANCE MEASUREMENTS PART I.
[Show full text]
Model 372 Series 3 Ohmmeter INSTRUCTION MANUAL
Model 372 Series 3 Ohmmeter INSTRUCTION MANUAL About this Manual To the best of our knowledge and at the time written, the information contained in this document is technically correct and the procedures accurate and adequate to operate this instrument in compliance with its original advertised specifications. Notes and Safety Information This Operator’s Manual contains warning headings which alert the user to check for hazardous conditions. These appear throughout this manual where applicable and are defined below. To ensure the safety of operating performance of this instrument, these instructions must be adhered to. Warning, refer to accompanying documents. Caution, risk of electric shock. Technical Assistance SIMPSON ELECTRIC COMPANY offers assistance Monday through Friday, 8:00 am to 4:30 pm Central Time. Contact Technical Support or Customer Service at (715) 588-3311 or visit our website at http://www.simpsonelectric.com Warranty and Returns SIMPSON ELECTRIC COMPANY warrants each instrument and other articles manu- factured by it to be free from defects in material and workmanship under normal use and service, its obligation under this warranty being limited to making good at its factory or other article of equipment which shall within one (1) year after delivery of such instrument or other article of equipment to the original purchaser be returned intact to it, or to one of its authorized service centers, with transportation charges prepaid, and which its examination shall disclose to its satisfaction to have been thus defective; this warranty being expressly in lieu of all other warranties expressed or implied and of all other obligations or liabilities on its part, and SIMPSON ELECTRIC COMPANY neither assumes nor authorizes any other persons to assume for it any other liability in connection with the sales of its products.
[Show full text]
The OHM Meter an Ohmmeter Is an Electrical Instrument That Measures
The OHM meter An ohmmeter is an electrical instrument that measures electrical resistance, the opposition to an electric current. Micro-ohmmeters (microhmmeter or microohmmeter) make low resistance measurements. Megohmmeters (aka megaohmmeter or in the case of a trademarked device Megger) measure large values of resistance. The unit of measurement for resistance is ohms (). The original design of an ohmmeter provided a small battery to apply a voltage to a resistance. It uses a galvanometer to measure the electric current through the resistance. The scale of the galvanometer was marked in ohms, because the fixed voltage from the battery assured that as resistance is decreased, the current through the meter would increase. Ohmmeters form circuits by themselves, therefore they cannot be used within an assembled circuit. A more accurate type of ohmmeter has an electronic circuit that passes a constant current (I) through the resistance, and another circuit that measures the voltage (V) across the resistance. According to the following equation, derived from Ohm's Law, the value of the resistance (R) is given by: On the ohms ranges of a normal multimeter the unknown resistance is connected in series with a battery and the meter and the scale reads backwards. A variable resistor is included in the circuit so that the meter can be adjusted to read full scale with the test terminals shorted (Fig 1). In the shunt ohmmeter a battery and variable resistor are connected across a milli ammeter and the resistor is adjusted so that the meter reads full scale with the test terminals are unconnected (Fig.2).
[Show full text]