Abstract: A handheld HVAC/R test and measurement instrument having a display, a keypad, a microprocessor, memory, and circuitry adapted to receive inputs from a plurality of sensors and to automatically determine the type of each sensor and automatically determine and display which HVAC/R tests and measurements are available to be performed by the field service technician using only the plurality of sensors. Different kits of sensors are used for various tests and measurements routinely performed when servicing HVAC/R systems, and the handheld instrument automatically identifies the sensors connected to it and leads the technician through the tests and measurements that can be performed using those sensor inputs in combination with technical reference information and calculation algorithms stored in memory.