User`s guide

Description
This command stores a null value in the multimeter's Null Register.
This command is provided for compatibility with the 34401A 6½
Digit Multimeter. For the 34410A, 34411A, or L4411A it is
recommended that you use the individual (null per function) null
commands found in the [SENSe:] subsystem, rather than the null
function provided by the CALCulate:NULL:OFFSet command. Avoid
using both types of nulls, as unexpected results may occur (they
are additive).