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42 HP E1312A/E1412A Multimeter Application Information Chapter 2
Two Ways to Store the
NULL Offset Value
• The null value is stored in the multimeter’s Null Register. You can
enter a specific number into the null register using the
CALCulate:NULL:OFFSet <value> command. Any previously stored
value is replaced with the new value. Use the following commands to
activate the
NULL function and input a null value. The calculate state
must be enabled before you can store a value in the Null Register.
CONF:<function> Clears the null offset value.
CALCulate:FUNCtion NULL Set math function to NULL.
CALCulate:STATe ON Enable math operation.
CALCulate:NULL:OFFSet <value> Store a null offset value.
• Another way to enter the null value is to let the multimeter store the
first reading in the register. After you enable the
NULL function with
the
CALC:STATe ON command, the first measurement you obtain will
be zero (if you have not stored a value as described in the previous
bullet). The measured value is stored as the
NULL offset value and
subtracted from itself to result in the zero reading. All subsequent
measurements will have the offset value subtracted from them. If you
previously stored a
NULL offset value using
CALC:NULL:OFFS <value> as in the commands in the above bullet,
the first reading does not overwrite the stored offset value but returns
with the previous offset value subtracted.
CONF:<function> Clears the null offset value.
CALCulate:FUNCtion NULL Set math function to NULL.
CALCulate:STATe ON Enable math operation.
** Set up the system to generate the offset of concern (e.g., short
** input leads for 2-wire ohms measurements that will follow).
READ? Measures and stores the offset value.
dB Measurements Each dB measurement is the difference between the input signal and a stored
relative value, with both values converted to dBm.
dB = reading in dBm - relative value in dBm
• Applies to dc voltage and ac voltage measurements only.
• The relative value is adjustable and you can set it to any value between
0dBm and
±
200.00dBm (well beyond the multimeter’s measurement
capabilities).
• Clearing the relative value. The relative value is stored in volatile
memory; the value is cleared when power is removed, after the module
is reset or after a function change.