Thermal control for a test and measurement instrument

The subject invention generally concerns cooling systems for electronic equipment and in particular concerns a variable fan-speed control for electronic test equipment. A cooling system for a test and measurement instrument including a variable-speed fan, useful with different instruments having different configurations, employs a plurality of sensors disposed at predetermined locations within an enclosure of the instrument, and is software programmable with predetermined parameters of each particular configuration of each particular instrument. At least one of the sensors measures the temperature of a component that dissipates power at a substantially constant rate, and at least one of the sensors does not include a heat source to provide heat for measurement.