Nulling an HP 431B Power Meter

[Radra]

Can anyone tell me how to utilize the "NULL" feature of the 431B power
meter? Have both a 431B and 431C but no manuals, so am unsure if I am
making proper use of this front panel null feature.

 

[Ulrich Bangert]

Radra,

the "Null" feature is used to remove offsets that may arise in the internal
circuitry of the power meter. So if you notice a nonzero indication of the
meter with no rf power applied to the sensor, simply press the "Null" bottom
to get a zero reading of the meter. Probably you may have to repeat this a
number of times. You will need this feature only in the most sensible
measure ranges, say 100 microwatts downward.

Regards
Ulrich

 

[Theo v. Werkhoven]

The carbonbased lifeform Ulrich Bangert inspired sci.electronics.equipment with:

Radra,

the "Null" feature is used to remove offsets that may arise in the internal
circuitry of the power meter. So if you notice a nonzero indication of the
meter with no rf power applied to the sensor, simply press the "Null" bottom
to get a zero reading of the meter. Probably you may have to repeat this a
number of times. You will need this feature only in the most sensible
measure ranges, say 100 microwatts downward.

Do not forget to terminate (50Ohm) the sensor first, otherwise the
calibration is invalid.
It is also advisible to let the 431 warm up first, or you'll be
repeating the calibration a couple of times.

Theo