User`s guide

Remarks
To use the null value, you will also need to turn on the null state with the
[SENSe:]CAPacitance:NULL[:STATe] command.
When using this command, it is recommended that you not turn on the
separate null state with the CALCulate:FUNCtion command. If you do, the
individual ("per function") null value set with this command, and the global
null value set with the CALCulate:NULL:OFFSet command will be additive.
A Factory Reset (*RST command) or an Instrument Preset
(SYSTem:PRESet command) clears all null values.
The null value is stored as part of the stored state with the *SAV
command.