Production of Damping Force

Production of Damping Force Points : Production of Damping Force The damping torque should be of such a magnitude that the pointer quickly comes to its final steady position, without overshooting.

If the instrument is “Under damped” the moving system will oscillate about the final steady position with a decreasing amplitude and will take some time before it comes to rest.

When the moving system moves rapidly but smoothly to its final steady position, the instrument is said to be “critically damped” or “dead beat”. If the damping torque is more than what is required for critical damping, the instrument is said to be “over damped”. In an over damped instrument, the moving system moves slowly to its final steady position in a lethargic fashion. The readings are very tedious to take.

Illustrate the way an under damped, an over damped and a critically damped system moves to its final steady position.

The damping device should be such that it produces a damping torque only while the moving system is in motion. To be effective, the damping torque should be proportional to the velocity of the moving system but independent of the operating current. It must not effect the controlling torque or increase the static friction.