A Wide—Band Audio Phasemeter

The problem of measuring the phase angle between two sinusoidal voltages is an important one in laboratory procedure. Phasemeters which can make this measurement accurately over a substantial frequency range have heretofore been bulky and relatively stationary. This paper describes a circuit which results in a phasemeter which is accurate to about 30 minutes, has a dial adjustment which is independent of frequency, operates over a range of from 20 c.p.s. to 100 kc and is relatively small and inexpensive. The principle used is to match the phase shift between the unknown voltages with a calibrated phase shift in the meter channel. This phase equalization is observed on a standard oscillograph which is used only as a comparison instrument. The oscillograph amplifier phase shifts are balanced out with an uncalibrated phase shifter cascaded in the meter channel and do not affect the measurement.