A method and apparatus for evaluating the functionality and sensitivity of an infrared sensor to infrared radiation. The method and apparatus are adapted for testing an infrared sensor having a diaphragm containing a heating element and a transducer that generates an output responsive to temperature. The method entails placing the infrared sensor in a controlled environment, and then exposing the diaphragm of the sensor to different levels of thermal radiation so as to obtain outputs of the transducer at different output levels. In the absence of exposure of the diaphragm to thermal radiation, flowing current through the heating element at different input levels so that the output of the transducer returns to the different output levels obtained using thermal radiation, the input difference between the input levels can be computed and used to assess the functionality and the sensitivity of the sensor.