An electronic instrument used to test an external defibrillator to ensure compliance with performance specifications. The device connects to the output of the defibrillator, typically via contact plates, and measures the energy delivered by the defibrillator into a standard resistive load; it may also perform transcutaneous pacemaker testing, provide waveform information, and execute other quality control procedures. The device may be used to test the function of an external defibrillator periodically, after repair, or for training purposes.