What is Ammeter | Definition, Types, Summary

What is ammeter?

Ammeter is a meter used to measure electric current flowing in a circuit. The unit of electric current is ampere hence the name ammeter (ampere +meter).

The symbol of ammeter is as shown below.

Ammeter is always connected in series with the circuit whose current is to be measured. In other words the current flows through the ammeter. As shown below.



The ammeter consists of set of coils. These coils get deflected when current flows through them.

Below are types of ammeter based on their construction and working.

1.      Permanent magnet moving coil

2.      Moving iron ammeter

3.      Electro dynamometer ammeter

4.      Rectifier ammeter

Also ammeters are classified as AC ammeter and DC ammeter.

Let us discuss every type in detail.

1.      Permanent magnet moving coil – here the coil comprises of a conductor and magnetic poles. Conductor is placed between the two magnetic poles. Whenever current flows through the coil the conductor gets deflected due to magnetic field. The deflection depends upon the magnitude of current flowing. This type of ammeter is only used for measurement of DC current.

2.      Moving coil ammeter – similar to permanent magnet coil the conductor is placed between the poles. Whenever the current flows through the coil the conductor deflects in a specific angle. This type of ammeter is used to measure both AC as well as DC currents.

3.      Electro dynamometer - it is comprised of both permanent magnet and moving coil. Here there are two coils one responsible for magnetizing and another for torque. This type of ammeter is used to measure both AC and DC currents. This type of ammeter is more accurate as compared to moving coil and permanent magnet.

4.      Rectifier ammeter – this type of ammeter consists of a rectifier unit, which changes the direction of current. Output of rectifier unit is connected to the input of permanent magnet moving coil. This type is used for the measurement of AC current.

Points to remember:-

·        DC ammeter has polarity, AC ammeter does not have.

·        Magnetization is the principle used for measurement of electric current.


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