A tachometer is a device used to measure the rotational speed or angular velocity of a rotating object, such as an engine, motor, or machine component. It provides a real-time indication of the speed at which the object is rotating, typically measured in revolutions per minute (RPM).

Tachometers can be broadly classified into two types: contact and non-contact tachometers.

  1. Contact Tachometers: These tachometers require physical contact with the rotating object to measure its speed. They typically use a mechanical or optical sensing mechanism to detect the rotational motion. The device is equipped with a probe or sensor that is pressed against a rotating part, and it counts the number of rotations over a specific time period to calculate the RPM.
  2. Non-contact Tachometers: Also known as optical or laser tachometers, these devices measure the rotational speed without making physical contact with the object. They use light or laser beams to detect the reflective or non-reflective markings on the rotating surface. By analyzing the changes in light intensity or reflections, the tachometer determines the rotational speed.

Both contact and non-contact tachometers have their advantages and are suitable for different applications. Contact tachometers are generally more accurate and can work in various environments, but they require direct access to the rotating part. Non-contact tachometers, on the other hand, offer convenience and can measure the speed from a distance but may have limitations with certain types of surfaces or lighting conditions.

Tachometers are widely used in automotive, manufacturing, and maintenance industries for tasks such as measuring the rotational speed of engines, motors, conveyor belts, fans, and other rotating machinery. They are also used in research and development, quality control, and troubleshooting applications.

Modern tachometers often come as handheld devices with digital displays for easy reading and may include additional features such as data logging, peak hold, and programmable settings. Some tachometers can also measure parameters like total revolutions, linear speed, and frequency.

When selecting a tachometer, consider factors such as the type of measurement (contact or non-contact), range of speeds to be measured, accuracy requirements, ease of use, and any specific features needed for your particular application.