Keysight DAQ970A Guide D'utilisation page 166

3 Features and Functions
dB Scaling
Selects dB scaling for the present measurement function. The result is the difference between the input signal and a
stored dB relative reference value, with both values converted to dBm:
To configure, select scaling function as dB and press Settings to open the configuration menu.
The reference value can be a measurement converted to dBm (Measure Ref Value softkey), or you can specify a
reference value (dB Ref Value softkey). Press Clear dB Ref to clear the reference value for dB measurements.
166 Keysight DAQ970A/DAQ973A User's Guide