User`s guide

Description
This command disables or enables the autozero mode for resistance
measurements.
When autozero is ON (default), the instrument internally disconnects the
input signal following each measurement, and takes a zero reading. It
then subtracts the zero reading from the preceding reading. This removes
offset variations present on the instrument's input circuitry that might
affect measurement accuracy.
When autozero is OFF, the instrument uses the last measured zero
reading and subtracts it from each measurement. It takes a new zero
reading each time you change the function, range, or integration time.
In the ONCE mode, the instrument takes one zero reading, and then sets
autozero to off. The zero reading taken is used for all subsequent
measurements until the next change to the function, range, or integration
time. If the specified integration time is less than 1 PLC, the one zero
reading is taken at 1 PLC to ensure best noise rejection in the zero
reading, and then the subsequent measurements are taken at the
specified fast integration time (for example 0.02 PLC).