Ammeter: what is it, function, types, operation

O ammeter is an electrical device that determines the intensity of the electric current passing through conducting wires or devices belonging to the electrical circuit. It is capable of measuring direct and alternating currents, for this it needs to be placed in series in the electrical circuit.

Read too: What is the speed of electric current?

Topics in this article

  • 1 - Summary about the ammeter
  • 2 - What is an ammeter?
  • 3 - Types of ammeter
  • 4 - How the ammeter works
  • 5 - Ammeter formulas
  • 6 - Other electrical magnitude meters

ammeter summary

  • An ammeter is a device that measures electrical current.

  • It can be analog or digital.

  • In electrodynamics, we divide it into real and ideal.

    • The real ammeter has internal resistance.

    • The ideal ammeter has zero internal resistance.

  • The accuracy of the electrical current measurement varies according to the value of the internal resistance of the ammeter.

  • There are several measuring equipment in addition to ammeters, such as voltmeters, ohmmeters and multimeters.

What is ammeter?

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The ammeter, also called clamp meter, is a electrical current intensity measuring device on lead wires and installed devices. Because of this, it is commonly used in electrical engineering, in the studies of industrial and residential electrical circuits.

O The name ammeter comes from the unit of measurement for electric current known as an ampere., being a tribute to the scientist André-Marie Ampère (1775-1836). It is commonly represented in electrical circuits by:

Ammeter symbol.

ammeter types

the ammeters can be analog or digital, however, have the same constitution inside, composed of an electromagnetic device known as galvanometer, which measures the low-intensity electric current or potential difference between two terminals. However, in electrodynamics, ammeters are considered to be real or ideal.

  • Ideal ammeter: is what we idealize, the one who does not have electrical resistance inside and that, when installed in electrical circuits, does not interfere with their operation, causing the electrical current and Electric tension in the circuit do not have their values ​​changed.

  • real ammeter: it is what really exists, since it has an internal electrical resistance, albeit with low intensity, which can interfere with the electrical circuit. So, to avoid this problem, it is necessary to ensure that the electrical resistance of the ammeter has a value lower than the electrical resistance of the circuit.

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How does the ammeter work?

The ammeter works as soon as the electric current runs through the electrical circuit, being able to measure both direct currents (whose direction of electrons does not change with time) as the alternating currents (whose sense of electrons changes with time), and it is also possible to adjust the desired measurement accuracy.

 Correct installation of the ammeter.
 Correct installation of the ammeter.

In order for it to measure the current correctly, must be installed in series in the circuit, as shown in the image above, due to the existence of an internal resistance. So, the lower the internal resistance of the ammeter, the better your current measurement will be.

Read too: How to calculate the electrical energy consumed by household appliances?

ammeter formulas

As the ammeter measures the value of the electric current in electric circuits, then, to determine the value of the current, we use Ohm's 1st law, represented by:



\(U=R\cdot i\)

  • u is the potential difference (ddp), measured in Volts [V].

  • R is the electrical resistance, measured in Ohm [Ω].

  • i is the electric current, measured in Ampere [A].

Other electrical magnitude meters

In addition to ammeters, there are other meters of electrical quantities, such as voltmeters, ohmmeters and multimeters.

Voltmeters are equipment that we use to measure the electrical voltage between two terminals of an electrical circuit. Ohmmeters are equipment used to measure the electrical resistance in a wire or resistor installed in the electrical circuit. And the multimeter is the name given to the device that combines the functions of ammeter, voltmeter and ohmmeter, being the most complete and most used.

By Pâmella Raphaella Melo
Physics teacher

Would you like to reference this text in a school or academic work? Look:

MELO, Pâmella Raphaella. "Ammeter"; Brazil School. Available in: Accessed on June 29, 2022.
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