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List non contact type transducer and compare them on the basis of any two factors.

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1 Answer

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Magnetic pick-up
This tachometer generator consists of a metallic tooth rotor mounted on the shaft whose speed is to be measured.
This method of measuring speed of rotation consists of mounting an opaque disc on the rotating shaft.
A magnetic pick-up is placed near the toothed rotor. The magnetic pick-up consists of a housing containing a small permanent magnet with a coil wound round it.
The disc has a number of equidistant holes on its periphery. At one side of the disc a light source is fixed like LED and on other side of the disc, and on the line of the light source, a light sensor like phototube or some photosensitive semi conducting device is placed.
Since the number of teeth is known the speed of rotation can be determined by measuring the frequency of pulses with an electronic counter.
N = f/HN Since the number of holes on the disc is fixed, the speed is a function of pulse rate.
A typical rotor has 60 teeth thus if the counter counts the pulses in one second, the counter will directly display the speed in rpm.
The pulse rate can be measured by an electronic counter which can be directly calibrated in terms of speed in rpm.

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