What is Photoelectric Tachometer? | Definition & Explanation

Hello friends, today we are going to talk about what photo electrical is; then we will go to this article, what are its advantages, what are its advantages and are its disadvantages, and how it is used.

What is a Photoelectric Tachometer?

Definition: A tachometer is commonly used to measure the speed of a motor. The speed of a motor is measured using light using a meter. This is known as a photoelectric tachometer. Its main body consists of a large diameter plate with a medium of light and an opaque dish with a hole in the laser.


A photoelectric tachometer consists of a transparent dish that is fitted to the shaft of the motor by which it is used to measure the speed of the motor.

You make holes in the plate at equal distances. The light medium is placed on one side, and the light sensor is placed on the other side of the plate. They are in line with each other.

When this disk has rotated, the hole on it starts rotating, and the opaque part is in the plate and alternately comes between the light medium and the light sensor. Passes and enters the sensor This way, a pulse is generated, which is used to measure the speed of the motor.

When the no opaque part on the plate comes in through the light medium and the sensor, the no opaque light on this plate blocks the medium so the output is not generated. 2 main factors cause pulse formation.

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1. The number of holes on the plate.
2. Speed ​​of turning the plate.

We cannot change the number of holes on the plate, so the pulse depends on the speed at which the plate rotates. By which the pulse is generated, which is used to measure the speed of the motor.

Advantages of Photoelectric Tachometer

The advantages of a photoelectric tachometer are as follows

  • Digital voltages get output, so analog is not required for digital conversion.
  • A continuous pulse is obtained after the ongoing work which simplifies the electronic circuit.

Disadvantages of Photoelectric Tachometer

The Disadvantages of a photoelectric tachometer are as follows

  • The medium life of light is short. So it needs to be replaced on time.
  • The accuracy of this method depends on the error generated by the unit pulse.
  • As many mistakes as possible can be made using the gating system.
  • The gating system means that the meter measures the frequency by calculating the input pulse.

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Hey, I am Vishnu Patil and I'm an Electrical Engineer and Electrical maestro. I have more than 10 years of experience with electricals. Through ElectricalGang I want to spread my knowledge with everyone else.

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