What is an Ammeter : Circuit Diagram and Its Types

We know that meter is an electronic device used to measure a particular quantity and it is associated with the measurement system. Similarly, the ammeter is nothing but ampere-meter used to measure ampere value. Here ampere is the unit of current and ammeter is used to measure current. There are two kinds of electric current namely AC and DC. AC changes the flow of current direction at regular intervals whereas the DC supplies the current in one direction. This article discusses an overview of what is an ammeter, circuit, types, and applications.

What is an Ammeter?

Definition: A device or instrument that is used to measure the current is called the ammeter. The unit of the current is ampere. So this device measures the current flow in ampere is named as an ammeter or ampere meter. The internal resistance of this device is ‘0’ however in practical; it has some amount of internal resistance. The measuring range of this device mainly depends on the resistance value. The ammeter diagram is shown below.


The working principle of an ammeter mainly depends on resistance as well as inductive reactance. This device includes extremely less impedance because it must include less amount of voltage drop across it. It is connected in series because the flow of current within the series circuit is the same.

The main function of this device is to measure the flow of current with the help of a set of coils. These coils have very low resistance & inductive reactance. The ammeter symbolic representation is shown below.

Ammeter Circuit Diagram

The construction of ammeter can be done in two ways like series and shunt. The following circuit represents the basic circuit diagram and the connection of the ammeter circuit in series and parallel are shown below.


Once this device is connected in series in the circuit, then the total measurand current will flow through the meter. So the loss of power occurs within ammeter due to their internal resistance & the measurand current. This circuit includes less resistance so less voltage drop will occur within the circuit.


Here, the resistance of this device is kept small due to the reasons like the total measurand current will flow throughout the ammeter and less voltage drop will occur across the device.


When the high current flows through this device, the internal circuit of the device will be damaged. To overcome this problem in the circuit, the shunt resistance can be connected within parallel to the ammeter. If the huge measurand current supplies throughout the circuit, the main current will pass throughout the shunt resistance. This resistance will not have an effect on the function of a device.

Classification/Types of Ammeters

These are classified into different types based on their applications which include the following.

  • Moving Coil
  • Electrodynamic
  • Moving-iron
  • Hotwire
  • Digital
  • Integrating

Moving Coil

This type of ammeter is used to measure both AC & DC. This device uses magnetic deflection where the flow of current through a coil will make to move within the magnetic field. The coil in this device moves freely moves between permanent magnet poles.


This type of ammeter includes a moving coil to rotate in the generated field through a fixed coil. The main function of this device is to measure AC & DC with an accuracy of 0.1 to 0.25%. The accuracy of this device is high when compared with the moving coil & permanent magnet moving coil. The device calibration is the same for AC & DC.


This type of ammeter is used to calculate alternating currents & voltages. In this device, the movable system includes specially created soft iron pieces, which move as acted upon through the electromagnetic force of a fixed coil of wire. These types of devices are classified into two types like repulsion and attraction. This device includes different components like moving element, coil, control, damping & reflective torque.

Hot Wire

This is used to measure AC or DC by transmitting it through a wire to make the wire heated and expand is known as a hot wire. The working principle of this device is to increase the wire by providing heat effect from the current supply through it. This is used for both AC & DC.

Digital Ammeter

This type of device is used to measure the flow of current in amperes & displays the values of on a digital display. The designing of this device can be done by using a shunt resistor to generate a calibrated voltage that is proportional to the flow of current. These instruments provide information regarding the current draw & continuity in order to assist the consumer to troubleshoot variable loads & trends.


In this device, the flow of current is summed over time and gives the product of time & current. These devices calculate the whole energy supplied through the circuit in a specified interval of time. The best example of this integrating device is watt-hour meter as it measures the energy directly in watt-hour.

Effect of Temperature in Ammeter

The ammeter is easily influenced by external temperature. So the temperature change will cause a fault in the reading. To overcome this, swamping resistance is used because the temperature co-efficient of this resistance is zero. In the following circuit, the ammeter & the swamping resistance is connected in series so that the effect of temperature on this can be reduced.


This device includes a fuse to protect from external heavy current. If the flow of current through the circuit is high, then the circuit will damage and the ammeter will not measure the flow of current until it is replaced with others. In this way, the temperature effect on this device can be reduced.


The applications of ammeter include the following.

  • The applications of this device will range from the schools to industries.
  • These are used to measure the current flow in the buildings to ensure that the flow is not too low or too high.
  • It is used in manufacturing and instrumentation companies to check the functionality of the devices
  • It is used with a thermocouple to check the temperature.
  • Electricians frequently use these devices to check the faults of the circuits in the building.


1). What is the function of an ammeter?

A measuring device used to measure the flow of current within the circuit.

2). Who invented ammeter?

In the year 1884, Friedrich Drexler has invented the first ammeter like moving-iron meter.

3). What is the SI unit for the electric current?


4). What is AC Ammeter?

The device used to measure the AC that supplies through an electric circuit is known as AC ammeter.

5). What is the formula for the current?

According to Ohm’s Law Current (I) = Voltage (V)/Resistance (R)

Thus, this is all about an overview of an ammeter and resistance of an ideal ammeter is zero. From the above information, finally, we can conclude that these devices are very essential for measuring current in various electrical and electronic circuits. Here is a question for you, what is the function of MC type ammeter?