What is Voltmeter: Definition and 151 Discussions

A voltmeter is an instrument used for measuring electric potential difference between two points in an electric circuit. It is connected in parallel. It usually has a high resistance so that it takes negligible current from the circuit.
Analog voltmeters move a pointer across a scale in proportion to the voltage measured and can be built from a galvanometer and series resistor. Meters using amplifiers can measure tiny voltages of microvolts or less. Digital voltmeters give a numerical display of voltage by use of an analog-to-digital converter.
Voltmeters are made in a wide range of styles, some separately powered (e.g. by battery), and others powered by the measured voltage source itself. Instruments permanently mounted in a panel are used to monitor generators or other fixed apparatus. Portable instruments, usually equipped to also measure current and resistance in the form of a multimeter, are standard test instruments used in electrical and electronics work. Any measurement that can be converted to a voltage can be displayed on a meter that is suitably calibrated; for example, pressure, temperature, flow or level in a chemical process plant.
General-purpose analog voltmeters may have an accuracy of a few percent of full scale and are used with voltages from a fraction of a volt to several thousand volts. Digital meters can be made with high accuracy, typically better than 1%. Specially calibrated test instruments have higher accuracies, with laboratory instruments capable of measuring to accuracies of a few parts per million. Part of the problem of making an accurate voltmeter is that of calibration to check its accuracy. In laboratories, the Weston cell is used as a standard voltage for precision work. Precision voltage references are available based on electronic circuits.

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  1. A

    Vintage EEG Gain compared to modern voltmeter

    I got from my drawer last night a vintage Brainmaster 2E I bought late 1990s that I used only a few times during that period. It has serial port at back. I don't know if it will work using a USB to serial port adapter connected to my laptop. Do you think it will work? My question concerns the...
  2. Leo Liu

    I Why does an ideal voltmeter have infinite resistance?

    Context: What I don't understand is why the little current that flows through the converted voltmeter can affect the measurement when the resistance of the resistor added to the ammeter is not infinite. Can someone please explain this to me? Thanks.
  3. Dario56

    Understanding the Role of a Voltmeter in Electrode Potential Measurement

    Voltmeter is an instrument which measures electric potential difference between two points. When measuring electrode potential of some redox system (vs SHE for example), it is said that voltmeter reading contains sum of all potential differences present in a cell. This includes all...
  4. W

    I do not sell these, an actual non-contact VOLTMETER

    Came across this today, and thought the crew here would find it interesting. ( If not appropriate - feel free to remove...) https://www.fluke.com/en-us/product/electrical-testing/clamp-meters/377-fc 30V is not too accurate, but NC Voltage, PowerQuality AND Datalogging...
  5. greg_rack

    Tension measured by a voltmeter of given bottom scale and current range

    First and foremost, I've studied voltmeters and ammeters on my own, and online there aren't many resources to do so... forgive me in advance for eventual silly questions/doubts :) I managed to calculate(intuitively) a tension of ##30.0V## per resistor, with basic procedures. However, I'm...
  6. B

    Voltmeter problem from (OCR paper) multiple choice

    As you can see when the switch is open it measures the voltage across the battery or emf I am assuming when calculating the internal resistance when the switch is closed voltage is 6 right so the internal resistance is 6/2 =3 which is not correct. answer is A Does this mean when the switch is...
  7. Rasias

    How to calculate what a voltmeter measures with multiple resistors?

    I tried to solve it by removing the voltmeter and simplifying it to just one resistor, then calculate the individual volts and then the deltaV, but still didn't found the answer, can you guys help me?
  8. Shivang kohlii

    Reading of a voltmeter having resistance R across a resistance

    Homework Statement The potential difference across resistance R carrying current I is V = IR . Now if the potential difference is measured via voltmeter of resistance r , the reading on voltmeter is V' . Prove that V' = Ir/(R+r) . For what value of r does the voltmeter measure true value...
  9. Krushnaraj Pandya

    Voltmeter readings across a closed/open switch in circuits

    Homework Statement The following figure shows a circuit containing a bulb, switch and battery. Four voltmeters are connected in it to measure potential difference. Which voltmeters give non-zero readings and which ones read terminal potential difference when the switch is 1) open and 2) closed...
  10. M

    Engineering Voltmeter and ammeter calculation in a circuit

    Homework Statement [/B] Hello, basically I have some tasks about calculating the reading of voltmeter and ammeter in a circuit, I can solve these with simpler circuits, where voltmeter is reading a few elements, but as in the ones below, I'm not sure where to begin and what to add into the...
  11. P

    EMF of a battery and voltmeter

    Homework Statement We have to measure emf of a battery. We have to voltmeters. Each of them when connected alone across the battery, they read V1 = 0.9V and V2 = 0.6V and when both of them are connected to the battery simultaneously, they both read V3 = 0.45V . What is the emf of...
  12. D

    High voltage circuit with voltmeter in between

    Homework Statement You have a voltmeter with an internal resistance of 10 MΩ. You would like to measure a very large voltage source, but you notice that this overwhelms your voltmeter, and you begin to get inaccurate results if the voltage is too high. You design the circuit shown above as a...
  13. EEristavi

    Battery condition check via voltmeter (with/without Load)

    Hello, I read article how to check battery condition appropriately (e.g. car battery). (Link: https://www.allaboutcircuits.com/textbook/direct-current/chpt-11/battery-ratings/ ) It's written that: in order to get better results, one must check under load. I'm not EE - I study physics and...
  14. M

    I What Caused the Lower Resistance in the Second Graph?

    Hi, in laboratory i had a sample of Ge with p-doping. In a first place i have done different measure V vs I (first image) Then i insert the sample in a magnetic field perpendicular to the sample. And i have done measure of V vs B (with a fixed current at 8 mA) and i obtained the second image...
  15. A

    Questions about Using My Multimeter

    So I'm fairly new to electronics. I took physics 2 in college and thought I'd give the hobby a try. I started with a very basic circuit. Just a power supply connected to a light-bulb. However, as simple as it was, I had several questions when taking the reading of my circuit with a multi-meter...
  16. G

    What does this voltmeter measure?

    Homework Statement Consider the following circuit where i(t) is sinusoidal and exists across both components. (1) is an inductor and (2) is a capacitor. The ideal voltmeters measure effective value. What is the value measured by V2: [![enter image description here][1]][1] [1]...
  17. Tony Meloni

    Question about Full scale deflection

    Homework Statement hello, just came across this type of question for first time. A voltmeter with a range of 0-30volts is to be used to measure a 120 volt circuit. calculate the value of the resistor to be placed in series with the meter. the sensitivity of the meter is 1000 ohms per volt ...
  18. J

    Voltmeter Ammeter and percentage error in R

    Homework Statement Homework EquationsThe Attempt at a Solution I am not able to understand how percentage error in R is calculated using the given circuits. Should I assign currents in the branches and write KVL equations ?
  19. D

    Ammeter and Voltmeter in Series

    Homework Statement Hi! A battery of emf 12 V and negligible internal resistance is connected to a resistor of constant resistance 6 Ω, an ideal ammeter and an ideal voltmeter. The voltmeter and ammeter are in series with the cell and the resistor. What is the reading on each? Homework...
  20. K

    Why you can't measure voltage and current at the same time?

    In my physics textbook it says that ammeter in circuit C shows higher current than ammeter in circuit A and D. And the voltmeter shows higher voltage in D than in B, and C. It's explained in the book that way: some electric current is passing through the voltmeter in C, thus the ammeter will...
  21. H

    Help me understand how electrical meters work

    Recently I asked why with a multimeter you should not measure the resistance of a fuse in a car while there was still power reaching the fuse but why it was ok to measure the voltage. I was told the way resistance is measured is a small current is sent by the meter for the calculation to be...
  22. J

    Reading of a voltmeter and an ammeter

    Homework Statement Homework EquationsThe Attempt at a Solution Part a) Voltmeter can be replaced by an open circuit and ammeter can be replaced by a short circuit .By doing so the current flows in the outer loop consisting of both the batteries and both the resisters .The current in the...
  23. Asmaa Mohammad

    The reading of the ammeter and the reading of the voltmeter.

    Homework Statement In this circuit What will be the reading of the ammeter and that of the voltmeter when: 1. Key S1 and key S2 are open. 2. Key S1 and key S2 are closed. 3. Key S1 is closed and key S2 is open. (Neglect the internal resistance of the source) Homework EquationsThe Attempt at a...
  24. G

    Voltmeter Reading for Ohm's Law Problem

    Homework Statement Homework Equations Ohm's Law (V=IR) The Attempt at a Solution These are my two attempts at getting to the solution. I'm really finding it difficult to tackle this question (our teacher gave it as an optional challenge). The provided answer on the worksheet is ɛ/2, but I...
  25. A

    Why there's a reading on the voltmeter connected to coil Q?

    Homework Statement The current in coil P is constant. An iron rod is inserted into coil P. Coil Q is placed next to P with a voltmeter connected to it. Explain why, during the time that the rod is moving, there is a reading on the voltmeter connected to coil Q Homework Equations emf=-Dphi/dt...
  26. Epoch

    Electricity: voltage calculation in serial

    Homework Statement Calculate the voltage U. The voltmeter gives a value of 80V. The Attempt at a Solution [/B] 3RI + 4RI - U = -80 How can I create a System of Linear equations if I have only one equation? Do I miss something? My answer sheet says U = 150V.
  27. akaliuseheal

    Calculating voltage which voltmeter is showing

    Homework Statement Schematic of circuit is not given, only the text which I translated into English. Using a voltmeter with internal resistance of 6k ohm, voltage between two points, 1 and 2 of a circuit of constant current, is measured to be 8v. Then, using a voltmeter with internal...
  28. R

    Current through voltmeter and ammeter

    3. The Attempt at a Solution As temp decreases, the resistance of the thermistor increases...doesn't this mean that the voltmeter will increase too since V=IR? I know that the total resistance of the circuit has increased so less current, but I put down option D but the correct answer is A?
  29. Biker

    What is the impact of an open circuit on voltmeter readings?

    Homework Statement What is the reading on voltmeter 1 and 2 when K is open? http://blob:http://imgur.com/2d84e21a-63e2-4021-b4d9-e37231816d38 Homework Equations There isn't any. The Attempt at a Solution Okay so I have two answers for ##V_1## and ##V_2##: What I am thinking is that it...
  30. moenste

    Reading of the voltmeter with closed switch

    Homework Statement (a) In the circuit shown below E is a cell of source (internal) resistance r and the resistance of R is 4.0 Ω. With the switch S open, the high resistance voltmeter reads 10.0 V and with S closed the voltmeter reads 8.0 V. Show that r = 1.0 Ω. (b) If R were replaced by a...
  31. moenste

    Resistance of the resistor and voltmeter's readings

    Homework Statement A battery of EMF 12.6 V and internal resistance 0.1 Ω is being charged from a DC source of EMF 24.0 V and internal resistance 1.0 Ω using the circuit shown in the figure below. V1 and V2 are high resistance voltmeters and R is a fixed resistor. (a) What is the polarity of...
  32. moenste

    Resistance of the voltmeter

    Homework Statement A battery is known to have an EMF of 5.0 V but when a certain voltmeter is connected to it the reading is 4.9 V. The battery can deliver a current of 0.40 A when connected to a resistance of 12 Ω. What is the resistance of the voltmeter? Answer: 24.5 Ω. 2. The attempt at a...
  33. moenste

    Difference in EMF of 5000 V and a voltmeter reading of 40 V

    Homework Statement A power supply used in a laboratory has an EMF of 5000 V. When, however, a voltmeter of resistance 20 kΩ is connected to the terminal of the power supply a reading of only 40 V is obtained. (a) Explain this observation. (b) Calculate (i) the current flowing in the meter and...
  34. moenste

    Resistance of the voltmeter

    Homework Statement When a particular voltmeter of fixed resistance R, which is known to be accurately calibrated, is placed across the 1.8 kΩ resistor in the diagram below it reads 2.95 V. When placed across the 4.7 kΩ resistor it reads 7.70 V. (i) Why do these two readings not add up to 12 V...
  35. moenste

    Voltmeter reading in a parallel circuit with two batteries

    Homework Statement In the circuit below the batteries have negligible internal resistance and the voltmeter V has a very high resistance. What would be the reading of the voltmeter? Answer: 9.6 V. 2. The attempt at a solution I used the Kirchhoff's rule: the current that flows from 10 V is...
  36. moenste

    Find the voltmeter reading in a circuit

    Homework Statement The 4.0 V cell in the circuits shown below has zero internal resistance. An accurately calibrated voltmeter connected across YZ records 1.50 V. Calculate (a) the resistance of the voltmeter, (b) the voltmeter reading when it is connected across Y'Z'. What do your results...
  37. moenste

    DC milliammeter as a voltmeter

    Homework Statement A DC milliammeter has a full-scale deflection of 10 mA and a resistance of 50 Ω. How would you adapt this to serve as a voltmeter with a full-scale deflection of 150 V? Comment on whether this voltmeter would be suitable for accurately measuring the potential difference...
  38. moenste

    Calculate the voltmeter reading

    Homework Statement The light-dependent resistor (LDR) in the circuit below is found to have resistance 800 Ω in moonlight and resistance 160 Ω in daylight. Calculate the voltmeter reading, Vm, in moonlight with the switch S open. If the reading of the voltmeter in daylight with the switch S...
  39. Mohamed_Wael

    Can a voltmeter read micro-volts?

    I am a mechanical engineer who is doing an experiment to measure a pressure drop across a microchannel, the sensor is measuring around 30 microvolt/mmHg which is very low value. I would like to know if the voltmeter can read this small value or not and if not what are the alternatives so I can...
  40. O

    Why does a voltmeter measure a voltage across inductor?

    The potential difference across an inductor is supposed to be zero, but a voltmeter measures it to be L*dI/dt. Also, if the p.d is zero then the electric field in the wires of the coil will be zero and in that case, why should charges flow at all? What am I missing?
  41. L

    Ammeter vs Voltmeter: Error Comparison

    Which one contributes more error when performing a lab calculating the voltage and current through different ohms of resistance? One was in parallel, the others in series and the last one both in series and parallel. They are systematic errors, but not sure which one would contribute more error...
  42. B

    Voltage-divider and d'Arsonval voltmeter problem

    The voltage-divider circuit is designed so that the no-load output voltage is 8/10ths of the input voltage. A d'Arsonval voltmeter having a sensitivity of 200 ohms/V and a full-scale rating of 150 V is used to check the operation of the circuit. a) What will the voltmeter read if it is placed...
  43. D

    Battery voltage increases when voltmeter connected

    When I connect a AA rechargeable battery directly to a voltmeter, voltage increases slowly, regardless of the way I connect it. I can't figure out why.
  44. Z

    Calculating voltmeter resistance in DC circuit

    Homework Statement initial problem: A 228 −Ω resistor and a 586 −Ω resistor are connected in series across a 90.0−V line. A voltmeter connected across the 228 −Ω resistor reads 24.0 V . Find the voltmeter resistance. For Req, i got Req=228R/(2+228), R being the resistance of the voltmeter. But...
  45. Suraj M

    The Inner Workings of a Voltmeter: Demystifying the Conversion from Galvanometer

    In a recent Viva one of my friends was asked this- " Why don't we use a normal Voltmeter instead of converting a galvanometer into a voltmeter?" I didn't quite understand what the examiner meant Isn't a galvanometer with a high resistance is what present inside a voltmeter? Same goes for an...
  46. alsy

    Voltage query -- A power supply, resistors and a voltmeter....

    Homework Statement a 12v dc supply is connected across 2 100k resistors in series.a voltmeter having sensitivity of 10,000 ohms per volt is switched to its 10v range and is connected to its 10v range and is connected to measure the voltage of 1 resistor. Homework Equations 1)sketch circuit...
  47. M

    Voltmeter values drop w/ time when measuring elec chem cell?

    I set up a zinc-copper elctrochemical cell by placing both electrodes in lemon juice to test the ability of lemon juice to conduct a current. I used a voltmeter and attached each lead to one of the metal electrodes. What I observed was that the voltage over time given on the voltmeter began to...
  48. X

    Can I Build a 3-Phase Voltmeter for Testing Motorcycle Alternators?

    Hi, I'm trying to build a voltmeter that will simultaneously measure all three phases unloaded of a 3-phase permanent-magnet alternator off a motorcycle (Honda Goldwings mostly, not that that's relevant...) The way these are typically checked in the industry is to set a voltmeter to measure AC...
  49. CAH

    Uncertainty in ammeter and voltmeter?

    I set an ohm meter to record current in mA, smallest 0.01mA, I took three readings for several different resistances.. What would the uncertainty be? And the same for the voltmeter but reading in volts, smallest 0.01V
  50. D

    Would the reading in voltmeter change?

    I'm Referencing: Foundations of Electromagnetic Theory - 4th Edition by Reitz Here's where I'm struggling: Then take a look @ this crude diagram of a circuit I've drawn. A voltmeter probe marked P (red) is moving along the circuit (red arrow), while the black probe remains stationary...