There are two main ways to perform a one-time auto zero operation. If auto zero is disabled, whenever the instrument receives a 'SENS:XXXX:NPLC' command (where XXXX is either VOLT, CURR, or RES), the auto zero values will be updated without enabling the auto zero function for all measurements. For SourceMemory sweeps with different NPLC settings within the sweep, NPLC caching should be used (available in firmware revision C18 and later). When NPLC caching is utilized, the auto zero values are stored in memory and are only updated with the 'SYST:AZER:CACH:REFR' command. Generally, one of these two update commands is sent to the instrument periodically to compensate for the temperature drift. For example, imagine your test sequence involves taking 10 measurements and you need it to be as fast as possible. Therefore, you disable auto zero and set the measurement integration rate to be as fast as possible (in other words, NPLC=0.01). The ten-measurement test cycle is to run continuously, but the effects of thermal drift will be unsatisfactory. Therefore, before sending the 'INIT' command, which begins the test, send the 'SENS:VOLT:NPLC 0.01' command. Sending this command updates the auto zero values once, but auto zero remains disabled for the subsequent ten measurements for maximum speed.