We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What is a Tachometer?

By Damir Wallener
Updated May 23, 2024
Our promise to you
WikiMotors is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At WikiMotors, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject-matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

A tachometer is an instrument designed to measure the rotation speed of an object, such as a gauge in an automobile that measures the revolutions per minute (RPMs) of the engine's crankshaft. The word is derived from the Greek words tachos, meaning "speed," and metron, meaning "to measure." This device traditionally is laid out with a dial, a needle that indicates the current reading and markings that indicate safe and dangerous levels. Digital tachometers have become more common, however, and they give numerical readings instead of using dials and needles.

Uses in Automobiles

In their most familiar form, tachometers measure the speed at which mechanical devices rotate, which typically is indicated in RPMs. They are used to monitor the RPMs in automobiles because running the engine at excessively high RPM rates can drastically shorten the life of the engine. In some cases, a small generator is attached to the engine drive shaft, and the RPM measurement is based on the electric current generated by the device. This instrument might also simply measure the rate at which the ignition system sends sparks to the engine.

Use in Airplanes

Airplanes typically have one tachometer for each engine, and in those that use propellers, one is also needed for each. A plane's engines usually operate at higher RPMs than its propellers. By using separate instruments for the different parts, the plane's pilot or crew can know whether there is a problem with any particular part.

Laser Instruments

Traditional tachometers require physical contact between the instruments and the objects being measured. In applications where this is not feasible for technical or safety reasons, it might be possible for a laser to take measurements from a distance. Laser devices work by pulsing a tight beam of light against the rotating element. The rotating element will have one reflective spot, and the instrument measures the rate at which the light beam is reflected back. They can be permanent parts of the system, or they can be handheld for occasional spot measurements.

Medical Applications

A tachometer can even find uses in medicine. By placing a small, turbine-like device called a haematachometer in an artery or vein, a medical professional can use this instrument to estimate the rate of blood flow from the speed at which the turbine spins. This can be used to diagnose circulatory problems such as clogged arteries.

WikiMotors is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
By lakefarmer05 — On Oct 28, 2012

There are such apps in market which display the RPM of a running fan or gear set compatible with my iPhone 5, iPod touch and all 5th generation iPods. The Tachometer app for iPhone is really cool. It may be old news to some, but new to me and I'm totally impressed!

By anon280117 — On Jul 16, 2012

Does anyone know the socket size of a 70's sun tach? The one I have has a missing socket.

By anon145173 — On Jan 22, 2011

What is the mechanism involved in the working of a laser tachometer?

By anon110413 — On Sep 11, 2010

what is the necessity of selecting 21:42 mode for a four stroke vehicle and 22:44 for a two stroke vehicle when tachometer functions on sensing the pulse from the HD cord?

By anon86318 — On May 24, 2010

What a great website. Thanks for answering people's questions.

By anon60469 — On Jan 14, 2010

how about this tachometer? who has ever used it?

item No. is DT2234C by a company called Rinch Industrial In China.

By anon36910 — On Jul 15, 2009

How do you read a digital (light pulsing) tach with all the multiples? In other words, the rotating shaft appears still at the 275 RPM setting; then again at the 550 setting (275 x 2); then again at 825 (275 x 3) etc. How does one determine which is the correct RPM reading?

By anon1774 — On Jun 15, 2007

how do you test to see if tach is working?

By seasilence — On Apr 16, 2007

How does a tachometer work in an aircraft?

WikiMotors, in your inbox

Our latest articles, guides, and more, delivered daily.

WikiMotors, in your inbox

Our latest articles, guides, and more, delivered daily.