Driven motors produce voltage in proportion with their velocity. Tachometers measure that voltage and read out the corresponding velocity. The typical ratio is 30 or fewer volts per 1000 revolutions per minute, depending on the measured motor.

Some tachometers, like a digital tachometer, have readout displays; others signal to a control or throttle on a motor in order to tightly regulate speed. Some do both. Here is a breakdown of tachometer types, based on mounting, mobility and adaptability:

1. Hand-held tachometers are small and come in handy as needed, rather than for constant testing or speed regulation.

2. Portable tachometers have similar uses as hand-held, but are larger and may even come on a wheeled stand.

3. Stationary or fixed tachometers attach as needed for a given application, including panel mount.

4. Modular tachometers have various attachments that fit a range of components, or adjust the voltage or speed ranges the tachometer can handle.

Action Steps
The best contacts and resources to help you get it done

Buy tachometers that have the right parameters online

A particular tachometer model will service only a limited velocity range, so make sure the tachometer you buy will work for your specific application. Also, not all tachometers have the same level of accuracy. Determine the tolerances of your application and buy a tachometer than can keep you within your target range. Lastly, there are both contact and non-contact tachometers available.

I recommend: Calright Instruments carries hand-held tachometers, both optical and laser models. For a wider range of product types, including panel mount and industrial tachometers, the Herman H Sticht Company is a good place to shop.

Check out tachometer websites that carry the automotive tachometer

There are many sources for the auto engine tachometer, so if this is the type you're looking for, then search sites that specialize in auto applications.

I recommend: Summit Racing Equipment carries several auto tachometer brands. They also have many replacement parts. Auto Meter is another great place to look. They have well over 100 models of round, easy-mount auto tachometers for sale, with both analogue and digital tachometers for cars.

Find tachometers for sale that have the features you need

Of course, the features you'll want on your tachometer depend on what you need out of the device. Besides a range of electrical outputs, some are self-calibrate and others have timers or even alarms. Displays include everything from numbers to graphics. Also, tachometer interfaces are sometimes very simple and others operate with computer programs.

I recommend: Process Control Systems, Inc. has a line of industrial tachometers that have either digital or analogue display and a variety of output types, as well as complete packages that include calibration circuits. If you're looking for programmable input or outputs, set-point delays and other special features, also take a look at Electro-Sensors, Inc..

Tips & Tactics

Helpful advice for making the most of this Guide

• •  For engine applications that do not involve odometers, engine tachometers can record the hours an engine runs as an alternate gauge of the engine's lifetime use.