What is Ammeter: Definition and 89 Discussions

An ammeter (from ampere meter) is a measuring instrument used to measure the current in a circuit. Electric currents are measured in amperes (A), hence the name. The ammeter is usually connected in series with the circuit in which the current is to be measured. An ammeter usually has low resistance so that it does not cause a significant voltage drop in the circuit being measured.
Instruments used to measure smaller currents, in the milliampere or microampere range, are designated as milliammeters or microammeters. Early ammeters were laboratory instruments that relied on the Earth's magnetic field for operation. By the late 19th century, improved instruments were designed which could be mounted in any position and allowed accurate measurements in electric power systems. It is generally represented by letter 'A' in a circuit.

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  1. jaumzaum

    The REAL difference between a Galvanometer and an Ammeter

    Hello guys. I'm having some trouble to understand the real difference from the Galvanometer and the Ammeter. The best comment I saw in some forum was: Ammeter: ANY instrument used to measure electrical current Voltimeter: ANY instrument used to measure voltage difference Galvanometer: a...
  2. B

    New full scale deflection of an ammeter

    Question: My attempt: Does 4.75 amps for the full scale deflection seem okay? Thanks for any help!
  3. rexxii

    How do you solve this equation used to calibrate an ammeter?

    Please can someone tell me how to solve the below: we have been given: can someone please explain how we deal with two theatas? please ignore full stops wouldn't line up any other way!
  4. F

    How does a digital ammeter work?

    I am a student at a trade school, majoring in HVAC. My electricity for HVAC textbook has a chapter on electric meters. However, my textbook does a poor job of explaining how a digital ammeter works. My textbook has the following description of how digital ammeters work: "To make meters...
  5. 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...
  6. 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...
  7. VSayantan

    Current through an Ammeter in an Electric Circuit

    Homework Statement [/B] It is required to find the current through the ammeter, marked A, in the above figure.Homework Equations ##V=iR##The Attempt at a Solution I've redrawn the circuit as follows - But don't know how to obtain the value ##i_3##
  8. 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 ?
  9. 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...
  10. 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...
  11. H

    How Do Electrical Meters Like Voltmeters, Ohmmeters, and Ammeters 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...
  12. J

    Understanding Shunt Selection for Accurate Current Measurement in DC Systems

    I need to measure current in DC system. I have circuit breaker (125A), so 150A shunt is selected. On that shunt ammeter is connected. But that ammeter has 60mV, scale 0-150A. What does this 60mV means on ammeter? Is it correct?
  13. 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...
  14. 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...
  15. Asmaa Mohammad

    Determine the resistance of an ammeter.

    Homework Statement An inductor is connected in series with an AC source, the rms output voltage of it is 260V and a hot-wire ammeter reads 2A. If the ratio of the voltage across the ammeter to the voltage across the inductor is 5/12, determine the resistance of the ammeter. (Neglect the...
  16. Epoch

    Electricity: shunt calculation for ammeter

    Homework Statement We have an ammeter with 20Ω resistance and a range of 10mA or 0.01A. The different ranges are 3000mA, 300mA, 30mA. Calculate the shunt resistors a, b and c. Homework Equations The Attempt at a Solution Ia = 0.01A ; Ra = 20Ω ; I = 0.03A Ua = Ia ⋅ Ra = 0.01A ⋅ 20Ω =...
  17. Epoch

    Electricity: ammeter range calculation

    Homework Statement [/B] An ammeter has a range of 10mA or 0.01A and a resistor of 20Ω. Three shunts are used: R1 = 4Ω ; R2 = 2Ω ; R3 = 4Ω What will the different ranges be (m3, m2, m1)? The Attempt at a Solution [/B] I started by calculating the voltage: Ua = Ia ⋅ Ra Ua = 0.01A ⋅ 20Ω =...
  18. Samar A

    Hot Wire Ammeter: How it Works

    In my textbook it says:"in the hot-wire ammeter the pointer stands at a definite reading when the temperature of platinum-iridium becomes constant and the wire stops expanding. That is achieved when the rate of heat radiated by the platinum-iridium wire becomes equal to the rate of heat...
  19. T

    Using a multimeter as an ammeter

    Homework Statement When I connect just the multimeter (as shown in the diagram) to the power source by inserting the lead into the mA connection and change the setting to read the current on the multimeter, it reads 0. When I change the lead connection from mA to A, the power source circuit...
  20. 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?
  21. S

    Reading an Electrodynamic Ammeter with 6 A Range and 100 Divisions

    Homework Statement What will the pointer of electrodynamic ammeter show (its natural frequency of oscillation is 5 Hz), if its input is energized by current: a) i (t) = 1.5 + 4 sin (3146 t) b) i (t) = 1.5 + 4 sin (2 t) Ammeter has a range of 6 A and the scale has 100 divisions. Homework...
  22. moenste

    Current through ammeter with two batteries

    Homework Statement For the values shown in the figure below, calculate (a) the current through the ammeter A1, (b) the current through the ammeter A2, (c) the PD across R2. Assume that the internal resistance of each cell and the resistance of each ammeter is negligible. Answers: (a) 0.05...
  23. Abysmaltan

    Solving Circuit with Ideal Ammeter: 4.0 Ohm Resistance

    Homework Statement A circuit is setup with an ideal ammeter connected across the 4.0 ohm. What will the reading of the ammeter be? 2. The attempt at a solution I am not sure whether the question is testing my understanding on how an ammeter should be connected in a circuit or about how to...
  24. 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...
  25. S

    B Why is Parallel Connection of an Ammeter to a Battery Considered Unsafe?

    How come when an ammeter is placed in parallel with a resistor that is connected to a battery, the circuit is considered incorrect + "safe," whereas an ammeter connected in parallel with the whole battery is considered incorrect + dangerous? My guess is that it has something to do with the...
  26. C

    Why Does My Ammeter/Voltmeter Read Incorrectly?

    http://www.ebay.com/itm/291369928250?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT i bought this cheap ammeter/voltmeter off ebay. now, i bought 1 before but it was slightly different. the wires had blue red and black instead of blue yellow and green. this makes it confusing but...
  27. toforfiltum

    Change in ammeter reading due to change in resistance

    Homework Statement Homework Equations 1/R= 1/R1 + 1/R2 +... I1= R2/R1 x I The Attempt at a Solution I chose B because I thought that since total resistance in the branch of variable resistor has increased, the branch with ammeter will get a greater share of current. Since I'm not too sure...
  28. N

    Why is my D.C. ammeter reading fluctuating?

    Why is the reading on my D.C. ammeter fluctuating? As in the needle won't maintain at one spot, it'll sway left and right. Also, how do i ensure that the fluctuations are minimized?
  29. N

    Determining current from ammeter

    Homework Statement The ammeter reads 5.0A. Find I1, I2, and ε Homework Equations ΔV=IR The Attempt at a Solution I've never dealt with ammeters before so I'm very confused. To start, I tried breaking this into loops, and then used Kirchhoff's Law. I started with the left side, since I...
  30. 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
  31. F

    Ammeter from parallel to series, current change

    Homework Statement In the circuit shown, a student mistakenly connects a perfect ammeter(i.e. One of negligible resistance), in parallel with one of two identical resistors. The ammeter reads 0.40A. What would the reading have been if he had correctly connected the ammeter in series with the...
  32. I

    Series lc circuit and clamp-on ammeter

    In a series LC resonant circuit the capacitor acts to cancel out the inductance of the the circuit. With no inductance in the circuit the magnetic field will collapse. So my question is, with this collapse of the magnetic field will it be be harder to measure the current in the circuit with a...
  33. A

    Actual resistance of an Ammeter

    Hi, I want to use a digital ammeter to measure the current flow though a Raspberry pi. The Pi uses about 700mA and is 5V so its got a resiatance of about 7 ohms. Therefore something like 0.5 ohm ammeter will have a large voltage drop of about 0.3V which is way too large and would lead to the...
  34. A

    Experimental physics i am very frustrated -- convert galvanometer into an ammeter

    I am trying to convert galvanometer into an ammeter. But after finding Galvanometer resistance and shunt values, and cut a wire according to that thickness and connected. But still, the galavanometer reading is not similar to that of the standard ammeter reading connected in the circuit. Any one...
  35. U

    Connect ammeter before or after the load?

    Is there any issue to connect the Ammeter in the circuit before or after the load. According to me, the current should remain same in circuit and there should be no restriction for Ammeter connection so it can be placed anywhere in the circuit. please explain why as this question asked to me by...
  36. sophiecentaur

    How Does an Ammeter Work? | eBay Guide

    This is not promoting an advert - just look and see! There is a 'clip on' ammeter for sale on eBay and I can't imagine how it works. It claims to work by clipping it round a cable and the scale shows +/- 30A DC. I spent good money on a Hall Effect clamp meter when it looks like I could have...
  37. Hardik Batra

    How is a Galvanometer Converted into an Ammeter Using a Shunt?

    To make ammeter, Resistance of proper small value is joined in parallel to the coil of galvanometer.This resistance is called a shunt. For smaller resistance value, We can not use the smallest resistance wire that is directly wound on coil of galvanometer so the resistance will become...
  38. M

    Calculating Mean Square Value of a Thermoelectric Ammeter Circuit

    I don't understand a few things here. Firstly, here's the question: This is thermoelectric ammeter. Internal resistance can be ignored. 1. Find the mean square value of the circuit. 2. Find the value that is displayed on the ammeter (alternating current). In the textbook, the formula for the...
  39. B

    Thermo couple ammeter full scale deflection

    if thermo couple ammeter full scale deflection is 10 Amp, for 1/5 th scale what is the Reading?
  40. D

    Getting currents in ammeter, with some resistances.

    Homework Statement In the figure R1 = 1.29R, the ammeter resistance is zero, and the battery is ideal. What multiple of ε/R gives the current in the ammeter? Homework Equations V=IR, 1/R=1/R_1+1/R_2..(when resistances are parallel) etc The Attempt at a Solution since ammeter doesn't...
  41. Z

    Converting Galvanometer to Ammeter: Resistance Wire Placement

    Homework Statement how will you convert a galvanometer of resistance 150 ohm giving a full scale deflection for a current of 3 milli ampere to a ammeter of range 0 to 6 ampere?a uniform rsistance wire of length 60cm and 2 ohm is given.find the length of the wire required? Homework...
  42. A

    Converting a galvanometer to ammeter and voltmeter.

    How will you convert a galvanometer of resistance 12 ohms showing full scale deflection for a current of 3 milli ampere to (i) Ammeter of range o to 6 Ampere (ii) Voltmeter of range 0 to 18V.
  43. Q

    Why does it matter whether or not an ammeter has zero resistance?

    Apparently an ideal ammeter has zero resistance. But for a series circuit, why does it matter? The purpose of an ammeter is to give the reading for the amount of current going round a 'loop' of circuit. Having some resistance does not prevent the ammeter from giving a true reading, right? So...
  44. K

    Why must ammeter be connected in series?

    lets say you have a circuit consisting only of a resistor and battery. Is it absolutely necessary to connect an ammeter in series with the resistor to measure current through it, rather than in parallel? Current doesn't want to go through a resistor, so if you connect a much lower resistance...
  45. T

    How to add Ammeter in LT Spice Schematic?

    It may sound so silly question but I am trying for last 2 hours and no result. I have drawn the following schematic in LT Spice and want to add an ammeter in the black rectangle. In component menu, I don't find anything named ammeter. Any clue? Your help is appreciated.
  46. I

    Conversion of Galvanometer to Ammeter

    This is kind of a stupid question but...to measure high currents, a galvanometer is connected parallel to a shunt resistance so that most of the current passes through the shunt resistance but only a small amount of current passes through the galvanometer. But wouldn't this defeat the purpose of...
  47. V

    Ammeter and Voltmeter question?

    Homework Statement A ammeter and a voltmeter are joined in series to a cell . Their reading are A and V respectively. If a resistance is now joined in parallel with voltmeter, (a) Both A and V will increase (b) Both A and V will decrease (c) A will decrease V will increase (d) A will increase...
  48. S

    Doubt in Ammeter: Shunt Resistor or Inductance?

    The other day I happened to open an ammeter just out of curiosity. What I saw was that across the positive and negative terminals a wire of considerable thickness(almost equal to the thickness of wires we use for household joints) was wound..It just had 4 or 5 turns. I guess it should be the...
  49. S

    Calculating Current in a Circuit without an Ammeter

    Homework Statement An ammeter whose internal resistance is 63 ohm reads 5.25 mA when connected in a circuit comtaining a battery and two resistors in series whose values are 750 ohm and 480 ohm. What is the actual current when the ammeter is absent?Homework Equations V = IR Rseries = R1 + R2The...
  50. Femme_physics

    Circuit problem with ammeter and unknown resistance

    Homework Statement http://img811.imageshack.us/img811/6902/circuittosolve.jpg This circuit includes 4 resistors whose value of 3 of them is known and the forth resistor, Rx is unknown. They connected an ammeter A to the circuit and the current through it is 0. 1) Calculate Rx. Is the value...