Digital phase meter

Phase meters are rare instruments, even in the laboratory or workshop of audio and hi-fi engineers and enthusiasts. Perhaps that is because until the advent of reliable digital techniques it was fairly difficult to design an accurate direct-reading phase meter. In one commercial catalogue published in the 1970s, a phase meter is advertised as having "an accuracy of about 3 degrees from 10 Hz to 30 kHz". Clearly, for modern audio equipment, that is no longer acceptable. Another reason may be that a phase meter is a fairly specialized instrument: many engineers and technicians measure phase shift with the aid of Lissajous figures ( which do not give very accurate results either). The phase meter presented in this article is accurate to within 0.5° over the frequency range 10 Hz to 20 kHz.