Moving Coil Ballistic Galvanometer
Ballistic Galvanometer is a type of galvanometer that measures the current or voltage in an alternating current circuit. It is also known as a moving coil meter or a moving coil ammeter.
Ballistic Galvanometer Operation
Ballistic Galvanometer measures the current or voltage in an alternating current circuit by using a moving coil placed in a magnetic field. When the current passes through the coil, it produces a magnetic field that opposes the magnetic field in the magnetic circuit. This opposition causes the coil to move and its speed depends on the current magnitude and frequency. The moving coil then strikes a spring balance to rotate the pointer of the meter and indicate the value of the current or voltage being measured.
Ballistic Galvanometer has a low frequency response limit of about 1 Hz, so it is not suitable for high frequency measurements. It can be used to measure ac currents up to about 100 A or ac voltages up to about 1000 V.
Types of Ballistic Galvanometer
Ballistic Galvanometer can be classified into two types:
1. Moving Coil Type
2. Moving Iron Type
1. Moving Coil Type
In moving coil type ballistic galvanometer, the moving coil is made of copper wire wound around a non-magnetic bobbin. The bobbin is mounted on a pivot and connected to a pointer that indicates the value of the current being measured. The magnetic field is generated by a permanent magnet or an electromagnet. The moving coil ballistic galvanometer is used to measure the current in an alternating current circuit up to 100 Hz.
2. Moving Iron Type
In moving iron type ballistic galvanometer, the moving iron is placed inside a stationary magnetic field. The iron piece is mounted on a pivot and connected to a pointer that indicates the value of the current being measured. The iron piece moves back and forth inside the magnetic field when the current varies in the circuit. The moving iron type ballistic galvanometer is used to measure the current in an alternating current circuit up to 1000 Hz.
