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In 1820, Hans Christian oersted showed that an electric current might alter the course of a magnetic needle. The first galvanometer was invented after this event. The multiplier was invented by physicist Johann Schweigger and a German mathematician, and it was named after them. A galvanometer consists of a needle that is attached to a coil and allows the coil to move freely in a magnetic field. One or more permanent magnet poles can be used to create this field.
When power is provided to the metre’s coil, a magnetic field is generated by the current-carrying wire interacting with the permanent magnet field. This results in a twisting force known as torque. The torque here rotates the coil, which the left-hand rule explains. The current flowing all through the coil is equal to the deflection of the needle in the galvanometer. The purpose of this article is to provide an overview of a galvanometer and how it works.
What is a Galvanometer?
It is impossible to understand whether the current flows in an electrical or electronic circuit even when the loop/switch is closed. As a result, the flow of current in the circuit is measured using a galvanometer.
But what are the uses of galvanometers? A galvanometer’s primary function is to transform electrical energy into mechanical energy i.e. the current flowing through the magnetic field is converted into magnetic torque. The galvanometer operates similarly to an actuator because it provides a rotational torque that turns in the opposite direction.
How Does a Galvanometer Work?
The galvanometer operates on the principle of electromechanical transduction, in which it responds to the current it is exposed to based on the current’s strength and rate of flow.
Aside from these two elements, it responds to any type of stimulation, either strengthening or weakening the current. Among the many types of galvanometers available, the two most commonly used are presented below:
- The coil is mounted on pivots or suspended by thin metal strips in a moving-coil galvanometer.
- The needle situated on the pivot is a permanent magnet encircled by the coil in a moving-magnet galvanometer.
The current passes through the coil when the instrument is exposed to a direct current source. This charge flow creates a magnetic field around it, which acts against the permanent magnet, twisting the coil and pushing it towards the spring. The pointer, which represents the scale showing the electric current, moves due to the fluctuation. The current flowing through the coil controls the rotation direction, while the current’s strength defines the rotation quantity. Therefore, the pole components must be appropriately designed to make sure that the magnetic field is uniform. If not, you will get an excessive angular deflection of the pointer towards the current.
Galvanometers have been used since the 19th century. Even though modern technology has brought various gadgets that outshine this device, it remains one of the most popular choices for detecting or measuring the electric current flowing from and to a source.
Uses of Galvanometer
Other types of analogue measurement devices (e.g. light metres and VU metres) have employed galvanometers as display components to collect the sensor outputs of these metres.
Strip chart records with a galvanometer-driven pen could have an all-out frequency response of 100 Hz (hertz) and a deflection of a few millimetres.
Disk makers utilise moving-coil kind metre devices known as ‘voice coils’ to control the mechanical positioning servos in hard disc drives and CD/DVD players to keep mass (and thus, access times) as low as possible.
Construction of a Galvanometer
In constructing a galvanometer, a soft iron cylinder is enclosed in a frame whenever a coil is covered on it, and a permanent magnet or cylinder head magnet is placed in the frame’s region. There is an axial rod and pivot in the spindle shape. A magnetic needle or indicator’s principal function is to specify the readings on a scale. The scale’s readings are measured in amperes (A).
The galvanometer works because the current flowing in a current-carrying coil is in a stable magnetic field; therefore, the indicated magnetic needle deflects to record the measurement. Here are the steps in the construction of a galvanometer :
- T1 and T2 are two terminals.
- A fine wire should be hung from a metal attached to terminal T1.
- Attach a coil to the wire’s free end.
- Two horseshoe electromagnets surround this coil.
- Because torque is not generated when the coil is parallel to the magnetic field, ensure that it is slanted.
Moving Coil
The current-carrying portion of the galvanometer is a moving coil. This coil is either circular or rectangular. The amount of copper wire turns is included in this coil. The coil moves freely between permanent magnet poles in the vertical equilibrium axis. The iron core allows for less reluctance flux, resulting in a strong magnetic field that allows the coil to move freely.
Conclusion
A galvanometer is primarily used to measure extremely small currents in a circuit. The moving coil galvanometer is the most used form of galvanometer nowadays. When the instrument’s mechanical and electromagnetic damping are removed, it can be used as a ballistic galvanometer to measure small capacitances and charges.
