What type of instrument is used to test the operation or condition of equipment components?

The most appropriate term for an instrument used to test the operation or condition of equipment components is "test instrument." This designation encompasses a broad category that includes various specific tools designed for diagnostic purposes, such as multimeters, voltage meters, and oscilloscopes.

"Test instrument" captures the general idea of any tool used for assessment, making it suitable for a wide range of applications in building maintenance. It indicates the function of the equipment rather than the specific type of measurement or analysis being conducted, which is crucial in a maintenance context where many different components may require testing.

While multimeters and other specific devices do serve particular functions, referring to them collectively as "test instruments" highlights their role in evaluating and ensuring proper operation across various systems and components in a facility.