An ammeter is a device that measures the flow of electricity via a circuit as current. Read on to learn about its varieties and how it works.

An ammeter (short for ampere metre) is a measuring device that is used to determine the current in the circuit. The term comes from the fact that electric currents are measured in Amperes (A). The ammeter is normally wired in series with the circuit that will be used to measure the current. The resistance of an ammeter is normally low so that it does not produce a large voltage drop in the circuit being monitored.

What is an Ammeter?

A current measuring device, an ammeter, measures either direct current or alternating current. The Ampere is the unit (SI) of current. As the instrument measures the value in amperes, it is called an ammeter.

Ammeters were once laboratory instruments whose operation was dependent on the earth’s magnetic field. In the nineteenth century, the ammeter was invented. It may be placed in any position to obtain precise measurements.

What is the Operating Principle of Ammeter?

The fundamental principle is that it must have an inductive reactance and a very low resistance. The circuit needs a very low impedance because it must have a very low voltage drop across it and must be linked in series since the current in a series circuit is the same.

Also, the power loss will be low because of the low impedance. 

It will be practically a short-circuited channel if linked in parallel, with the whole current pouring into the ammeter, maybe causing it to burn. Thus, it has to be linked in series. An ideal ammeter must have zero impedance and zero voltage drop, resulting in zero power loss in the instrument. However, the ideal cannot be realised in practice.

The Classification of Ammeter

Based on the current passed, it is divided into the following categories:

DC Ammeter

AC Ammeter

The ammeter is classified as follows based on its construction and design:

Rectifier type ammeter

Electrodynamometer ammeter

Moving iron ammeter

Permanent moving coil ammeter

The AC supply is measured with a rectifier type ammeter.

The Electro-dynamometer ammeter is very precise and operates on AC and DC power.

The coil freely swings between the poles of a permanent magnet in a moving iron ammeter. 

Both direct and alternating currents may be measured with this ammeter.

A D’Arsonval metre or galvanometer is another name for a permanent moving coil ammeter. In a uniform magnetic field, one can observe the angular deflection of the coin to measure the current through a coil.

Ammeter Connection

When the ammeter and circuit (current) are connected in series, the device can measure the entire electron flow. The power loss of the device is caused by the ammeter’s internal resistance and the measured current. The circuit experiences a low voltage drop as low resistance in the ammeter circuit.

Ammeter Types

These are divided into many sorts based on their intended use. For instance:

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

This type of equipment measures current flow in amperes and presents the results on a digital display. This device may be designed using a shunt resistor to provide a calibrated voltage proportional to current flow. These devices give information on the current use and continuity to help customers troubleshoot fluctuating loads and trends.

Integrating Ammeter

The current flow is summed over time in this device, yielding the product of time and current. These devices determine the total energy delivered through the circuit in a specific time interval. The watt-hour metre is the most outstanding example of this integrating device since it measures energy directly in the watt-hour.

Hot Wire Ammeter

A hot wire is a device used to measure AC or DC by sending it through a wire and causing it to heat up and expand. This device’s method of operation is to grow the wire’s diameter by passing heat from the current supply through it. This applies to both AC and DC.

Moving-iron Ammeter

Alternating currents and voltages are calculated using this type of ammeter. The moveable mechanism of this gadget consists of specially designed soft iron bits that move when operated upon by the electromagnetic force of a stationary coil of wire. These devices are divided into two categories: repulsion and attraction. The reflected torque, damping, control, coil and moving element are all included in this device.

Electrodynamic Ammeter

A moving coil rotates in the produced field through a stationary coil in this form of the ammeter. This device’s primary function is to measure both DC and AC with an accuracy of 0.1 to 0.25 per cent. Compared to the moving coil and permanent magnet moving coil, this gadget has a high level of precision. Both AC and DC devices require the exact calibration.

Moving Coil Ammeter

This ammeter may be used to measure both AC and DC. This gadget employs magnetic deflection, in which current flowing through a coil causes it to move inside a magnetic field. This device’s coil swings freely between permanent magnet poles.

Applications of Ammeter

The following are some of the ammeter’s uses.

This gadget can be used in various settings, including schools and businesses.

These are used to check the current flow in buildings to ensure it isn’t too high or too low.

It is used to test equipment functionality in instrumentation and manufacturing firms.

It is used to check the temperature with a thermocouple.

Electricians routinely use these devices to check for defects in the building’s circuits.


So, what is an ammeter? An ammeter is a gadget or equipment that is used to measure current. The Ampere is the unit of current. Thus, an ammeter or ampere metre is a device that measures the current flow in amperes. Although the internal resistance of this gadget is ‘0,’ it has some internal resistance. The resistance value mainly determines this device’s measurement range. 

An ammeter’s functioning concept is primarily based on resistance and inductive reactance. This instrument has a very low impedance because it must have a very low voltage drop across it. Because the current flow in a series circuit is the same, it is linked in series.

The primary purpose of this gadget is to use a collection of coils to measure the flow of electricity. The resistance and inductive reactance of these coils are extremely low.