This paper describes a digital phase meter developed by the time‐based chopping method. The phase meter can: first, read out the phase by chopping it with a synchronous high frequency signal whose frequency, 3o MHz, is 10000 times faster than that of the phase carrier signal, and obtain 0.03 degrees resolution; second, judge the 0?2π+or 0 ? —2π‐periodicity and discriminate the ambiguity of phase lead/lag by differentiating the phase amplitude to extend the unambiguous measurement range to infinity; third, have the linear dynamic measurement range as large as ± 105·2πand fourth, simple and inexpensive. An optical fiber Mach‐Zehnder displacement interferometer is given as a typical application example of the digital phase meter.