Published on: 23 June, 2022

What are absolute & secondary instruments ? Why is damping required in a measuring instrument ?


Absolute instrument: These instruments give the magnitude if the quantity under measurement terms of physical constants of the instrument.

Secondary instrument: These instruments are calibrated by the comparison with absolute instruments which have already been calibrated.


Damping force or torque is also necessary to avoid oscillations of the moving system about its final detected position owing to the inertia of the moving parts and to bring the moving system to rest in its final deflected position quickly.

In the absence of damping, the moving system of an instrument would oscillate about the position at which the deflecting and restoring torques are equal. The function of damping is to absorb energy from the oscillating system and to bring it to rest promptly in its equilibrium position so that its indication may be observed.

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