What is Tachometer and its uses?

The tachometer is a measuring instrument that is used to measure the operating speed of an engine in revolutions per minute. It is also known as a revolution counter. The device can measure the rotational speed of the shaft or disc when the machine is in motion. It also indicates the angular speed of a rotating shaft. This instrument is usually used to estimate traffic speed and volume/flow. It is used in cars, aircraft or other vehicles. It shows the rate of rotation of engine crankshaft along with the marking that displays the safe range of rotational speed.

Working Principle of Tachometer:

An Electric Tachometer works on the principle of relative motion between the magnetic field and shaft of the coupled device. The motor of tachometer works as a generator, i.e. it produces the voltage based on the velocity of the shaft. It counts the number of rotations the crankshaft is making per minute. It is essential for the user to know the RPM of the engine and its operating range to avoid unnecessary damages. The device works on either an alternating or direct current.

Types of Tachometer:

  • Contact type – This type of tachometer is usually fixed to the machine or electric motor. It works by bringing a freely spinning wheel in contact with a rotating shaft or disc. The shaft drives the wheel to generate the pulses. These pulses are then read by a tachometer and measured in revolution per minute. It can also calculate the linear speed and distance.
  • Non-contact type – It is also known as photo tachometer or non-touch tachometer. This type of device doesn’t need any physical contact with the rotating shaft. It uses a laser, infrared light, or other light sources to take the measurements. The device sends out the beam of light. This beam reflects each time a tape makes a full rotation. The receiver needs to count these reflections during the process to measure the rotational speed in RPM. This type of tachometer is efficient, durable, accurate, and compact.
  • Electronic tachometer – It is made up of electronic components used to measure the engine speed. It measures the speed in revolution per minute. It is mainly used in the dashboard of the car to measure the driving speed. It uses a magnetic pickup placed near a rotating engine to generate electric pulses. These pulses have frequency proportional to the engine speed.
  • Analog tachometer – It is an electronic instrument that counts machine revolution based on time period. It reads the frequency with which coil’s current changes the direction. In case the engine turns more quickly, the change in the magnetic field becomes more radical by generating the higher voltage.
  • Digital tachometer – It is a digital device that measures the speed of the rotating object. It is an optical encoder that identifies the angular velocity of a rotating shaft or motor. It is commonly used in automobiles, airplanes, medical and instrumentation applications.
  • Time measuring tachometer – It calculates the speed by measuring the time interval between incoming pulses. It is more suitable for measuring low speed with high accuracy.
  • Frequency measuring tachometer – It calculates the speed by measuring the frequency of the pulses. The revolution of the device depends on the rotating shaft and is suitable for measuring the high speed. The modern version comes with a sophisticated digital circuit to perform the count, storage, calculation, display and reset to deliver output in rpm.
  • Mechanical tachometer – It has a centrifugal force on a rotating mass to stretch or compress a mechanical spring. It uses a series of consecutively tuned reeds to identify engine speed. It displays the engine speed by indicating the vibration frequency of the machine.

Accuracy, precision, contact, non-contact type, range, acquisition time, portable/fixed, analog/digital, and cost are the important factors that are considered while selecting the right type of tachometer.


  1. It is used to measure rotational speed.
  2. It can measure the flow of liquid with the help of an attached wheel with an inclined angle.
  3. It is applicable for the medical sector to measure the blood flow rate of the patients.
  4. It is used in vehicles to display the rate of engine crankshaft rotation.  


The tachometer is one of the crucial elements in industrial motor control. Few of its basic functions include monitoring of motor’s speed, counting, process control, and ratio/draw application. Whereas, it is applicable for equipment like conveyors, windmill, rotary feeders, grinders, dryers, augers, elevators, etc. And the suitable industries include power plants, recycling and chemical plants, automotive and material handling, food and beverage, paper mills, etc. Now, ensure the safety of your equipment and automobile by measuring the working speed of an engine and maintaining the safe speed range with the help of a tachometer. Some of our best selling tachometer includes Beetech HTM 560 - 99999 RPM Non Contact Tachometer, Kusam Meco KM 2234BL - 5 to 99999 RPM Non Contact Digital Tachometer, and Metravi NCTM 500 - 99999 RPM Digital Tachometer.