Accurate phase measurement with two sampling voltmeters

An accurate phase measurement technique is described. The technique uses two sampling voltmeters for signals with voltage ratio up to 1:1000 and a single sampling voltmeter with input switch for signals with voltage ratio up to 1:10. At 50 Hz, uncertainties below 0.05 m/spl deg/ were attained at voltages below 8 V and voltage ratios up to 1:10. This uncertainty rose to 15 m/spl deg/ at 10 kHz. When corrected for range-to-range phase differences, only slightly higher uncertainties are attainable for voltage ratios up to 1:1000. A technique for the automatic correction of range-to-range phase differences is described.