Damping Torque | Critical Damping | Images

Damping Torque :

Fluid friction damping
Due to deflecting torque, pointer moves in one direction while due to controlling torque pointer moves in oppositei direction.i
Due to these opposing torques, the pointer may oscillate in the forward and backward direction if the damping torque is not present.
Damping torque brings the moving system to rest quickly in its final position.
Damping torque acts only when the moving system is i actually moving. If moving system is at rest, damping torquei is zero. Thus final deflection of the instrument is not affected due to damping torque.
Different methods of producing damping torque are : Air friction damping
Eddy current damping

Critical Damping:

Depending on the magnitude of torque, damping may be classified as underdamped, overdamped or critically dampedi Effect of the damping on the deflection of the instrument 1s shown in Fig. 4.3.1.
If the instrument is underdamped the pointer will come t rest after some oscillations. If the instrument is overdamped, i pointer takes considerable time to obtain its final deflected position.
If the damping is critical, without oscillations and in shof time the pointer reach its final steady position.