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GALVANOMETER

DEFINATION INTRODUCTION PRINCIPLE CONSTRUCTION WORKING APPLI CATION

CONTENTS

Definition of GALVANOMETER

An instrument for detecting or measuring a small electric current by movements of a magnetic needle or of a coil in a magnetic field .

Instrument for measuring small electric current by deflection of moving coil.

This is analog electromechanical instrument.

Being a sensitive instrument can’t use for measuring the heavy amount of current.

Galvanometer were the first instrument use to detect and measure current.

INTRODUCTION

Galvanometer work on the principle of conversion of electrical energy into mechanical energy.

Basic principle of Galvanometer is PMMC(permanent magnet moving coil)

When current flow from moving coil generate magnet field and this field action with the permanent magnet field then produce a rotating torque in moving coil

WORKING PRINCIPLE

PARTS OF METER Permanent magnet Coil Cylinder Needle Scale Spring

Construction

When measure the current of any circuit connect Galvanometer in series of the circuit.

Current pass from the moving coil and produce a magnet field (Electro magnet flux) which directly proportional of the current .

Electromagnet flux and permanent magnet flux then produce a force (torque) in a coil and coil move.

WORKING

You can see in previous figure needle connect with moving coil needle move on the scale which calibrated.

Spring produce a torque opposite of rotating torque therefore when current is off then pointer still at zero.

We can use it as a Voltmeter

APPLICATION

Ammeter

One of the earliest type of galvanometer .Its represented by its name . In which a coil of fine wire is suspended vertically by fine metallic filament in the field of permanent magnet . The metallic filament acts as a tension element analogous to the metal band in the taut-band suspension system , but with a much lower to restraining torque constant. The suspension filament also serve as a conducting path between the galvanometer terminals and the moving coil.

Suspension Type Galvanometer

Instead of pointer The suspension

galvanometer has a small mirror attached to moving coil.

This mirror is used to deflect a focused light beam along a scale.

This light beam is equivalent to a very long pointer with almost no mass.