A phase-measurement offset compensation technique suitable for automation

DC offsets degrade the measurement of phase between two sinusoidal signals when the zero-crossing method is used. To improve the measurement accuracy, a novel offset compensation technique is introduced that is suitable for use in automated instruments. The technique is based on calculating the average value of two phase angles: one is between the offset crossings of increasing signals and the other is between crossings of decreasing signals. Thus, it is possible to dispense with the offset-minimization-dedicated hardware that exists in conventional phase meters at the expense of added software. Some hardware limitations and design considerations are discussed.