Keysight 478A, Руководство по эксплуатации и обслуживанию

Страница: 18 / 55

2 Operation
18 Keysight 478A Operating and Service Manual
Biasing Thermistors
Maximum Input
The model 478A/431 and 478A/432 combinations respond to the average RF
power applied. The maximum signal applied to the thermistor mount should not
exceed the limitations for
– average power
– pulse energy
– peak pulse power
Excessive input can permanently damage the model 478A by altering the match
between RF and compensation thermistors (resulting in excessive drift or zero
shift) or cause error in indicated power.
Average Power
The 478A/431 and 478A/432 combinations can measure average power up to 10
mW. To measure power in excess of 10 mW, insert a calibrated directional coupler
such as one of the Keysight Technologies model 770 series or 790 series between
the mount and the source. UNDER NO CIRCUMSTANCES APPLY MORE THAN 30
mW AVERAGE POWER TO THE MOUNT.
CAUTION
M echanical Shock: Do not drop or subject to severe mechanical shock. Shock
may destroy the match between thermistors and increase susceptibility to drift.
CAUTION
Before connecting the model 487A to the 431 or 432 power meters, set the
MOUNT RES switch to 200 W position. CONNECTING A 200 W MOUNT TO A
POWER METER SET FOR A 100 W MOUNT CAN RESULT IN THERMISTOR
DAMAGE.