Keithley Instruments, Inc., founded in 1946 by Joseph F. Keithley in Cleveland, Ohio, is a leading American developer and manufacturer of precision electronic test and measurement instruments. Headquartered in Solon, Ohio, the company specializes in instruments that measure low-level electrical signals, including voltage, current, and resistance. Its core product lines focus on Source Measurement Units (SMUs) such as the Series 2400, 2600B, 2450/2460/2470 Graphical Touchscreen SMUs, which integrate precision power supplies and measurement capabilities. The company also offers high-performance digital multimeters (DMMs) like the DMM6500 and DMM7510, as well as sensitive electrometers, picoammeters, and nanovoltmeters for ultra-low measurements. In the semiconductor and advanced materials sectors, parametric curve tracers (e.g., the 4200A-SCS Parameter Analyzer) are widely used for device characterization. Keithley provides comprehensive software solutions, including KickStart and LabVIEW drivers, to automate testing and data analysis. Since its acquisition by Tektronix in 2010, the company has operated as a subsidiary within the Fortive Corporation group, benefiting from global sales and support channels. Keithley is recognized worldwide for its technical leadership in sensitive measurements, serving R&D laboratories, university research, and industrial manufacturing with instruments that deliver industry-leading accuracy and sensitivity.