In AC loss measurements of superconductors using the four-terminal method, the voltage measured consists of two components. The loss voltage component is in phase with transport current while the inductive voltage is out of phase with transport current. Here we report on the use of a compensation coil to nearly cancel the inductive voltage. The loss voltage was amplified by a transformer amplifier and observed on a digital oscilloscope. The waveform of the measured voltage was compared with that of a calculated signal. The loss voltage was analytically calculated for a round wire using the critical state model. The effects of frequency on the waveform of the loss voltage are also studied. Finally, a comparison between waveforms of loss voltages obtained with sine-wave and triangle-wave transport currents are presented.