How do Digital Non-contact Tachometers work?

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How do Digital Non-contact Tachometers work?

Modern, digital tachometers can easily measure RPM with unmatched accuracy and precision, even across distances, without contact, using laser or infrared pointers.
Portable, hand-held, digital non-contact tachometers can measure precise rotational speeds and they can quickly tell you how fast an object, machinery or equipment spins.

How do Tachometers work?

A tachometer is a counting device. It counts how quickly a rotating object completes a full spin or how many times it rotates within a minute. This count is then used to measure the equipment’s rotational speed.

Tachometers are used to measure rotational speed in a wide range of applications and can be found everywhere, in bikes, cars, boats and airplanes and they help measure the Speed of the respective vehicles. Most tachometers display the speed as RPM or Revolutions per Minute.

What are handheld or portable Tachometers?

Portable Tachometers are used to measure the speed and RPMs of small motors, engines, fans or gears, though the device has greater, versatile application possibilities.
Digital, handheld Tachometers are even used to calibrate large tachometers that are used in aircrafts and big vehicles. They are also used to measure RPMs of industrial equipment like printers, machine lathes, gears, as well as everyday equipment like fans, lawn mower fans, generator fans, boat propellers, etc.
Nearly all of us have encountered tachometers in our daily lives.

What is the difference between contact and non-contact digital tachometers?

The difference between contact and non-contact Tachometers lies in the method of measurement of RPM, though both simply measure the rotational speeds.

Contact-type Digital Tachometers have attachments – tips, usually called Adaptors, that can rest against the spinning or rotating equipment or object. The adaptor spins along with the machine or object to calculate the RPM.

Contact measurements are not possible in cases where there are access or space restrictions or the equipment is hard to reach. Also, due to safety restrictions, the object or machinery might be at a distance, in a cage, or behind other protective equipment.
In these cases, the non-contact type of Digital Tachometers can measure the speed from a distance and are used to measure the revolutions, rotations or speed, using laser, infrared or other kind of light sources.
Non-contact Digital non-contact Tachometers are also called Photo Tachometers.

For non-contact measurements, a piece of reflective mark has to be placed on the spinning object – a reflective paint mark or a piece of reflective tape works – such that the rest of the spinning object has a dark or non-reflective surface.
Non-contact Digital Tachometers send out a beam of light that reflects each time it touches the reflective mark, on every full rotation. The device counts these reflections over time and displays the rotational speed in revolutions per minute.

Non-contact Tachometers use a laser pointer along with a reflective piece of tape or paint to measure RPM

What are the different types of Tachometers?

A wide variety of Tachometers exist and the respective features and components improve usability and range of applications. They are manufactured to suit different needs.

Analogue Bike Tachometer

Analogue Tachometers provide live and immediate measurements using a marked dial.

Digital Tachometers display the measurements on a LCD or LED display. Digital models can save some readings on the device memory, helping users to take multiple measurements and then using the collected data at a later time.

Advanced Digital Tachometers offer lots of features and advanced specifications, along with high resolution, precision and high accuracy. Some models can even measure RPM to a hundredth of a rotation with hardly any margin of error.
They even measure Rotation Speed, Total Revolutions, Frequency, Surface Speed and Length.

Some inexpensive, handheld Tachometers feature low-quality rubber adaptors that wear out fast. Most modern, digital Tachometers come with high-quality, durable, adaptor tips that last long.
Most handheld tachometers are lightweight and easy to carry around and use.

Where are Digital Tachometers used?

Handheld Digital Tachometers are used to check RPM and other spinning measurements of various types of equipment, like conveyors, windmills, rotary feeders, grinders, dryers, cooling equipment, augers and elevators. 
Some common industries that use these devices include power plants, recycling facilities, chemical plants, automotive plants, material handling, food/beverage manufacturing, paper mills, textile mills, etc.

Metravi offers a range of high-quality, portable, lightweight, handheld, Digital Tachometers with a host of features and varying measuring ranges and specifications; both Contact and Non-contact models, as well as combined ones!

DT-2235 Contact Type Tachometer

Contact type Tachometer, measures up to 50,000 RPM with an exclusive one-chip microcomputer LSI Circuit and Quartz Crystal Time Base. Features a 5 digits LCD display with an accuracy of ±0.05%.


NCTM-500 Non-contact Type Tachometer

Non-contact type Tachometer With Counter, Data Hold. Measures from 50mm to 200mm, RPM up to 99999 RPM and 99999 Counts with an accuracy of ±0.04%.


NCTM-1000 Non-contact Tachometer

Non-contact type Tachometer and Counter with Max / Min, Last Data Record, measures 2 to 99,999 RPM and 1 to 99,999 Counts with accuracy ±0.05% ±1 Digit.

Metravi NCTM-2000 Contact & Non-contact combined Digital Tachometer

NCTM-2000 Contact and Non-contact Combined Tachometer

Contact and Non Contact type Combined Tachometer featuring Max/Min, Last Record. Measures 20,000 RPM in contact mode and 99,999 RPM in non-contact mode with ±0.05% ±1 digits accuracy. Also measures Rotation speed, total revolution, frequency, surface speed and length.

Metravi NCTM-3000 Contact cum Non-contact combined Digital Tachometer

NCTM-3000 Contact and Non-contact Combined Tachometer

Contact and Non Contact type Combined Tachometer with non-contact laser sighting for measuring from up to 12 feet distance. Measures 20,000 RPM in contact mode and 200,000 RPM in non-contact mode with ±0.05% ±1 digits accuracy.

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Comments (2)

  • Deepak Wankhede Reply

    Dear Sir,

    Please see the Attached file.

    Urgently Required

    kindly send quotation for following items

    Our customer requirement …… Non contact tachometer Range = – 50 to + 1000

    Extech 461920
    Make – Extech (USA)

    If you need any further information pl. email me

    Best Regards,
    Deepak Wankhede
    Shree Enterprises,

    Shree Enterprises,
    “Geetai”, Gangapur Road, Near.- Prasad Circle, Opp- Upadhye Hospital, Maharashtra, Nashik – 422 013

    May 14, 2022 at 7:05 pm
    • Richa Reply

      Noted, Sir.

      May 15, 2022 at 9:00 am

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