Toothed Rotor Variable Reluctance Tachometer

Toothed Rotor Variable Reluctance Tachometer Points : Toothed Rotor Variable Reluctance Tachometer, Uses of Toothed Rotor Variable Reluctance Tachometer A toothed rotor variable reluctance tachometer is described here. This tachometer generator consists of a metallic toothed rotor mounted on the shaft whose speed is to be measured. A magnetic pickup is placed near the toothed rotor.

The magnetic pickup consists of a housing containing a small permanent magnet with a coil wound round it. When the rotor rotates, the reluctant e of the air-gap between pickup and the toothed rotor changes giving rise to an indicted e.m.f. in the pickup coil. This output is in the form of pulses, with a variety of wave shapes.

The frequency of the pulses of induced voltage will depend upon the number of teeth of the rotor and its speed of rotation. Since the number of teeth is known, the speed of rotation can be determined by measuring the frequency of pulses with an electronic counter. Suppose the rotor has “T’ teeth, the speed of rotation is “n” rps and number of pulses per second is “P”.

A typical rotor has 60 teeth. Thus if the counter counts the pulse in one second, the counter will directly display the speed in rpm. It is mentioned above that the pulses have a variety of wave shapes. This is immaterial, as this tachometer is always connected to an electronic counter, whose requirement is merely that the amplitude be great enough to trigger a count. Uses Variable reluctance tachometer probably is the most common type of tachometer in use today.