Phase displacement correction of reference channel in digital bridge used for calibation of instrument transformers with digital output

Phase displacements in the reference channel of a digital bridge used for calibrating instrument transformers with digital output have been investigated. Since the sampling in this set-up is controlled from the unit under test the largest correction stems from the virtual time shift caused by the aperture time integration when measuring a sinusoidal voltage with the sampling multimeter in DCV mode. This time shift is found to be equal to half the aperture time. In addition is the correction for the reaction time of the multimeter in this mode found to be 140 ns.