Use of precise digital voltmeters for phase measurements

The possibility of using high-resolution digital voltmeters for AC voltage measurements at a frequency of about 16 Hz is presented. The method of approximate synchronous sampling is used where each sample is measured as the mean value of the one-third cycle of a period. From the samples, the RMS value of the "derived" sine is determined using subsequent numerical synchronization, while the phase angle of the first sample is calculated as regression line coefficient. Corrections of phase differences between two voltmeters were determined using only one source in cascade measurements.