HP WaterSkis E1312A, WaterSkis E1412A manual DB Measurements, CONFfunction

Two Ways to Store the NULL Offset Value

dB Measurements

•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.

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.

42 HP E1312A/E1412A Multimeter Application Information Chapter 2