A vibration galvanometer is an electromechanical instrument used to measure small electrical currents. It is commonly used in applications where precise current measurements are needed, such as in laboratory experiments and electrical testing. The operation of a vibration galvanometer is based on the principle of converting electrical current into mechanical motion through electromagnetic forces.
Here's how a vibration galvanometer works:
Coil and Suspension System: The galvanometer consists of a small coil of wire suspended within the magnetic field of a permanent magnet. The coil is typically wound around a lightweight, non-magnetic frame.
Damping Mechanism: To prevent excessive oscillations of the coil, a damping mechanism is often incorporated. This can involve using air resistance or a fluid-filled chamber to dampen the coil's motion and bring it to rest more quickly after a measurement.
Electromagnetic Principle: When a current flows through the coil, it creates a magnetic field around the coil. This magnetic field interacts with the magnetic field of the permanent magnet, resulting in a torque being exerted on the coil according to Ampère's law.
Angular Displacement: The torque applied to the coil causes it to experience an angular displacement. This displacement is proportional to the magnitude of the current passing through the coil.
Mirror and Light Source: Attached to the coil is a small mirror. As the coil moves due to the applied current, the mirror moves as well.
Light Beam and Scale: A light source is directed toward the mirror, and the reflected light beam is directed onto a scale located at a distance from the mirror. The scale is calibrated to provide readings of current based on the deflection of the light beam.
Measurement: The deflection of the light beam on the scale indicates the magnitude of the current passing through the coil. The scale is usually calibrated in units such as milliamperes or microamperes, depending on the sensitivity of the galvanometer.
Vibration galvanometers are known for their high sensitivity and accuracy in measuring small currents. They are often used in scenarios where the current to be measured is very low and would be difficult to measure accurately using other types of ammeters. However, vibration galvanometers are relatively delicate instruments and require careful handling to maintain their accuracy.
It's worth noting that modern electronic instrumentation has largely replaced vibration galvanometers in many applications due to their ease of use, greater precision, and reduced susceptibility to mechanical wear and tear.