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Tachogenerator: Advantages vs Disadvantages

A tachogenerator, is an electromechanical device used for powering the tachometer, a device used for measuring the shaft speed in motors, engines and other types of rotational devices. The tachometers are designed to indicate the rotary speed of a shaft in a rotating position. The result is given as a number of rotations, recorded during the contact with the device or as a number of rotations per minute.


The main part of the tachogenerator is a rotating armature. It’s the part that is directly connected to the machine shaft, which speed is to be measured. Set in a fixed magnetic field, the rotation of tachogenerators induces electromotive force that is equal to the speed with which the shaft rotates. The contacts of the tachogenerators armature are conjoined to a voltmeter. The voltmeter is the device that displays the received voltage into a speed value.

The tachogenerator is used in broad range of measurement applications. Tachogenerators are used for producing power for measuring the shaft speed of wide range of electrical engines, motors as well as the speed of powered tools including machine tools, conveyors, fans, mixers and much more.


  • Convenient Output Voltage

The tachogenerator produces a convenient output voltage that can be measured with most conventional DC voltmeters. This means that you don’t have to invest in a special voltmeter to be able to measure the shaft speed of the devices you are testing.

  • Indicates The Direction Of The Rotation

The output voltage measured with the use of a tachogenerator, shows the direction towards which the shaft is rotating. This said, besides information about the speed, with this devices you get concrete information for the direction of rotation.


  • Possible Errors

Due to the variations in the contact resistance, you must keep n mind the probability of errors occuring. With that being said, the tachogenerators require periodic maintenance and brushes of the commutator.

  • Non-Linearity

It’s not uncommon for non-linearity to occur during the measurement of the powered speed produced by the tachogenerators. This is a result of the distortions that happens in the permanent magnetic field.