This paper presents a personal computer (PC) aided testing system that retrieves rotor speed, voltage, current and power factor of AC (single-phase or three-phase) and DC electric machines and displays them in time domain waveform formats. Taking advantage of the displayed waveform profiles, users are able to achieve a better understanding of electric machines than by using instruments typically adopted in the laboratory. The proposed testing system can be applied not only to ordinary electric machine experiments but also to special-topic studies in the undergraduate laboratory. Both the hardware configuration and software techniques instrumental in building the system are presented.