Correct option is D
Damping device: -
This device produces damping torque this torque is necessary to bring the pointer to rest quickly.
This damping torque (Td) is used to reduce the oscillation.
There are several types of damping used in measuring devices.
Fluid Damping: -
This involves the use of a fluid (often oil) to provide resistance to motion.
For example, in moving coil instruments, a vane attached to the moving system may move in a fluid, with the fluid resistance providing the damping.
This is commonly used in analog meters and mechanical gauges.
Air Damping: -
Similar to fluid damping but uses air as the damping medium.
In this method, a piston moves inside a closed chamber, and the air trapped inside provides the necessary damping force.
This is a simpler and cleaner method compared to fluid damping but might not provide as strong a damping effect.
Electrical Damping: -
In electric and electronic measuring instruments, damping can be achieved through electrical methods.
For instance, in moving coil instruments, damping can be provided by a short-circuited damping coil that generates a counteracting electromagnetic force.
Another example would be the use of resistive or resistive-capacitive (RC) circuits to absorb and dissipate the oscillatory energy.
Magnetic Damping: -
This method uses the interaction between a magnetic field and a moving conductor to provide damping.
When the conductor (often a metal vane or plate) moves through the magnetic field, it induces eddy currents that create an opposing force, which provides the damping effect
