Stores such as Amazon.com, eBay.com and Sears sell digital tachometers. Specialized tool suppliers, such as Harbor Freight Tools, Grainger Industrial Supply and Summit Racing, sell less-common tachometers, usually at a higher price.
Amazon.com sells a non-contact digital photo tachometer by CyberTech. Without contact, the tachometer measures the rotational speed with a visible red light beam using a high intensity class-two laser capable of measuring from 2.5 to 99,999 revolutions per minute with an error of 0.05 percent. The tachometer usually sells for more than 50 percent less on Amazon.com than from other retailers, as of 2015.
Grainger sells a digital tachometer that is capable of contact and non-contact measurements. The tachometer sold by Grainger can measure non-contact revolutions per minute from 10 to 99,999, as well as contact revolutions per minute from 0.5 to 20,000, with an accuracy of 0.05 percent.