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Encyclopedia of Electrical Engineering
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HOME TABLE OF CONTENTS
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Encyclopedia of Electrical Engineering
HOME TABLE OF CONTENTS PROJECTS TECHNOLOGY
HOME TABLE OF CONTENTS

Ammeter

What is Ammeter?

The meter uses for measuring the current is known as the ammeter. The current is the flow of electrons whose unit is ampere. Hence the instrument which measures the flows of current in ampere is known as ampere meter or ammeter.
Fig.no.1: Ammeter
The ideal ammeter has zero internal resistance. But practically the ammeter has small internal resistance.

Symbolic Representation

The capital alphabet A represents the ammeter in the circuit.
Fig.no.2: Ammeter Representation.

What are different types of Ammeter?

The following are the types of an ammeter regarding construction.
  • 1. Permanent moving coil ammeter.
  • 2. Moving iron ammeter.
  • 3. Electro-dynamo-meter ammeter.
  • 4. Rectifier type ammeter.
By the current, the ammeter categories into two types.
  • 1. AC Ammeter.
  • 2. DC Ammeter.

Connection of Ammeter in Circuit

The ammeter is connected in series with the circuit so that the whole electrons of measurand current passes through the ammeter. The power loss occurs in ammeter because of the measurand current and their internal resistance. The ammeter circuit has low resistance so that the small voltage drop occurs in the circuit.
Fig.no.3: Connection of Ammeter in Circuit.
The resistance of the ammeter is kept low because of the two reasons.
✔ The whole measurand current passes through the ammeter.
✔ The low voltage drop occurs across the ammeter.

Ammeter Shunt

The high-value current directly passes through the ammeter which damages their internal circuit. For removing this problem, the shunt resistance is connected in parallel with the ammeter.
Fig.no.4: Ammeter Shunt

How does an Ammeter work?

The main principle of Ammeter is that it must have very low resistance and also inductive reactance. It has very low impedance because it must have a very low amount of voltage drop across it and must be connected in a series connection because the current is the same in the series circuit.
Ammeters are used to measure electrical current by having the current move through a set of coils. In moving-coil ammeters, this movement results from the fixed magnets that are set opposite to the current. The movement then turns a centrally located armature that is attached to an indicator dial. This dial is set above a graduated scale that lets the operator know how much current is moving through a closed circuit.
All of the Ammeters and its functions will be discussed practically in the upcoming circuit analysis topics.