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Megha

Transducers that functions in reverse manner are known as inverse transducers. All those transducers used for measurement of nonelectrical quantities which exhibit excellent characteristics of operation when the input and output quantities are reversed, can be used as inverse transducers. They are known as output transducers we have already seen that the accuracy of feedback measuring systems depends on the characteristics of the physical system which is used to convert the output signal into a signal of desirable form and dimensions for comparison by the comparator. For each one of the output signals, a suitable system for use in the feedback path is to be chosen such that the quantities usually compared are torque, force-balance, or position-balance systems. In electronic signal processing amplifiers and other circuits, they are either voltage or current. It has been indicated that the physical system constituting the feedback path should possess excellent stability, high degree of linearity, and belong to the class of zero-order system. The choice of such systems thus becomes limited to a few inverse transducers. The permanent-magnet moving boil system, the parallel plate capacitor, and the piezoelectric crystal are exploited for thier application in the feedback measuring system with electrical output and the pneumatic bellows with mechanical output in pneumatic systems. The permanent magnet moving coil system is used to convert in torque-balance systems. The torque T developed is given by T = BANI Where B = flux density in the gap A = area of moving coil N = no. Of turns of the moving coil