Keithley Instruments is a measurement and instrument company headquartered in Solon, Ohio, that develops, manufactures, markets, and sells data acquisition products, as well as complete systems for high-volume production and assembly testing.

In September, 2010, the company agreed to sell itself to the Danaher Corporation, a Washington, D.C.–based conglomerate, for $21.60 per share.

His first product, the "Phantom Repeater," amplified low-level electric signals so that they could be measured by more standard equipment.

The company has approximately 500 products used to source, measure, connect, control or communicate direct current (DC), radio frequency (RF), or optical signals.

[buzzword] The company's markets are engineers, technicians, and scientists in manufacturing, product development, and research functions.