The differential probe and current probe may have a small bias.This bias should be eliminated before measurement, as it can affect measurement accuracy.Some probes have built-in automatic methods for eliminating bias, while others require manual removal.
Automatic elimination of bias
The probe with the TekVPITM probe interface is combined with the oscilloscope to eliminate any DC bias errors in the signal path. Press Menu button on the TekVPITM Probe and Probe Controls box appears on the oscilloscope to display the function of AutoZero.Selecting the AutoZero option automatically clears any DC bias errors in the measurement system. The TekVPITM current probe also has a Degauss/AutoZero button on the probe body.Pressing the AutoZero button eliminates any DC bias errors in the measurement system.
Manually eliminate bias
Most differential voltage probes have built-in dc zero offset trim control, which makes eliminating zero offset a relatively simple step: after the preparation is complete, the oscilloscope is set to measure the average voltage waveform.