| 摘要 |
A method and apparatus for determining the phase angle between two periodic square wave signals is disclosed in which the two square wave signals are applied to respective inputs of an exclusive OR gate, the output signal of which is applied to a first input of a digital selection circuit. The output signal generated by this digital selection circuit is passed through a low pass filter to form a time integral, arithmetic mean value which is digitized by an analog to digital converter and supplied as a numerical value to a digital computer. The digital computer applies logical signals to two additional inputs of the digital selection circuit. The computer is programmed to sequentially set these control signals such that the digital signal presented to the computer sequentially represents the mean value, an upper signal level value, and a lower signal level value of the square wave signal output by the selection circuit. The computer is programmed to use these three variables to calculate a corrected value of the phase angle and to display this calculated value on a display unit.
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