Working of Non-contact Tachometers

A tachometer is a device that measures the rotational speed of an engine or any other rotating
machinery, in RPM. It is used to monitor engine performance and avoid damage.

There are generally two types of tachometers: analog and digital.

• Analog Tachometers: These are the traditional types of tachometers that use a needle to indicate the RPM of an engine. Analog tachometers typically have a dial that displays the RPM range, and the needle moves around the dial to indicate the current RPM.
• Digital Tachometers: These use digital displays, such as LCD or LED screens, to show the engine RPM. Digital tachometers are often more accurate and precise than analog tachometers, and they may also offer additional features such as data logging and programmable warning signals.

How do Tachometers Work?

Tachometers work by measuring the rotational speed of an engine or any other rotating
machinery. The exact method used to measure the RPM can vary depending on the type of
tachometer, but the basic principle remains the same.

In analog tachometers, the device uses a magnetic pickup coil or a photoelectric sensor to detect
the rotation of a shaft or other rotating object. The signal generated by the pickup coil or sensor
is then amplified and converted into a mechanical movement of a needle that moves around a
dial, indicating the RPM.

In digital tachometers, the signal generated by the pickup coil or sensor is converted into an
electrical signal and processed by an electronic circuit, which displays the RPM on a digital
screen. Some digital tachometers use a microcontroller to process the signal and offer additional
features, such as data logging and programmable warning signals.

Contact-type tachometers require physical contact with the rotating object, and use a mechanism
such as a wheel or a pin to make contact with the object and detect its rotational speed.
Non-contact tachometers, on the other hand, use light or other forms of energy to detect the
rotational speed of an object from a distance.

Working of Non-Contact Tachometer

Non-contact tachometers use light or other forms of energy to detect the rotational speed of an
object from a distance. These types of tachometers are commonly used in situations where it is
not practical or safe to have physical contact with the rotating object. Here’s how a non-contact
tachometer works:

• Light source: A non-contact tachometer uses a light source, such as an LED or laser, to emit a beam of light towards the rotating object. The light beam can be either visible or invisible, depending on the type of tachometer.
• Reflective tape or mark: A small piece of reflective tape or a mark is attached to the rotating object. This tape or mark reflects the light beam emitted by the tachometer back towards the sensor.
• Sensor: The tachometer has a sensor that detects the reflected light beam from the rotating object. The sensor may be a photodiode, phototransistor, or other type of light- sensitive device.
• Signal processing: The signal generated by the sensor is amplified and processed by an electronic circuit. The circuit calculates the time it takes for the light beam to travel from the tachometer to the rotating object and back again, and uses this information to calculate the rotational speed of the object.
• Display: The calculated RPM is then displayed on a digital screen, which can be either a built-in display on the tachometer or a remote display unit.

Non-contact tachometers can be very accurate and are commonly used in applications such as
manufacturing, automation, and research. However, they may be affected by factors such as
ambient light, reflective surfaces, and distance from the rotating object, so it is important to
ensure that the tachometer is properly calibrated and used in the appropriate conditions.

In conclusion, non-contact tachometers offer several advantages over contact-type tachometers.
Since they don’t require physical contact with the rotating object, they can be used in situations
where it is not practical or safe to do so, such as in high-speed or hazardous environments. Non-
contact tachometers are also more convenient to use since they don’t require any special
attachments or preparation of the rotating object, and they can provide accurate and precise
measurements. Additionally, non-contact tachometers are often more durable and reliable since
they don’t suffer from wear and tear associated with physical contact. Overall, non-contact
tachometers are a valuable tool in industries such as manufacturing, automation, and research,
where precise measurements of rotational speed are essential for optimal performance and safety.