HP E4418A, Service Manual

Page: 52 / 108

Performance Tests
Power Reference Level Test
2-12 HP EPM-441A/442A Service Guide
The following procedure should be performed to allow you to calculate
P
meas
.
Note
The procedure details the key presses required on the
HP EPM-441A. For the HP EPM-442A the equivalent key presses
should be performed on both channels.
1. Set the DVM to measure resistance. Connect the DVM between
the V
RF
connector on the rear panel of the HP 432A and pin 1 on
the thermistor mount end of the sensor cable. Verify that no power
is applied to the HP 478A.
2. Round off the DVM reading to two decimal places and record this
value as the internal bridge resistance (R) of the HP 432A
(approximately 200
Ω
).
■
R ____________
Ω
3. Connect the equipment as shown in Figure 2-3, ensuring that the
DVM input leads are isolated from chassis ground.
Note Ensure that the HP 432A and the power meter under test have
been powered on for at least 30 minutes before performing the
following steps.
4. Press on the power meter.
5. Set the HP 432A RANGE switch to Coarse Zero. Adjust the front
panel Course Zero control to obtain a zero meter indication.
6. Fine zero the HP 432A on the most sensitive range, then set the
RANGE switch to 1 mW.
7. Set the DVM to measure microvolts. Connect the positive and
negative input leads, respectively, to the V
comp
and V
RF
connectors
on the rear panel of the test power meter.
8. Observe the reading on the DVM. If less than 400
µ
V, proceed to
the next step. If 400
µ
V or greater, press and hold the test power
meter Fine Zero switch and adjust the Coarse Zero control so that
the DVM indicates 200
µ
V or less. Release the Fine Zero switch
and proceed to the next step.
9. Round the DVM reading to two decimal places. Record this
reading as V
0
.
■
V
0
___________
Preset
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4402serv.book Page 12 Monday, March 11, 2002 11:34 AM