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Adjustments
Model 8902A
A 2 J 2
O
( F Y I N )
'
- - -
; : : : ;
000000
oono
0
AUDIO OSCILLATOR
91*
0
0
0
0000
0
0
0 0
0 0 0 0 0 0 L3
0000
0
0000
Adjustment 6-Voltmeter
Off set and Sensitivity
RECORDER
( R E A R
OUTPUT
PANEL1
-
D l B l T A L VOLTMETER
(Stop
1 )
INPUT
Reference
Service Sheets 14 and
15.
Description
The dc offsets
of
the audio peak and average detectors are first adjusted. The voltmeter sensitivity is
then adjusted while comparing the displayed reading to the level read by an external dc voltmeter.
The sensitivity
of
the average detector is adjusted while comparing the average mode to the peak
mode when detecting a sinusoidal signal.
Equipment
Audio Oscillator
.................................................................
H P 89038
Digital Voltmeter
................................................................
H P 3455A
Figure 5-3. Voltmdc.r
0JJ.kt
and Scnsifivity
A
djirstmcnt TLW
St>lirp
Procedure
1. Connect the equipment
as
shown in Figure 5-3. Do not connect the audio oscillator to the
Measuring Receiver at this time. (The Measuring Receiver's INPUT can be connected either
directly to the CALIBRATION RF POWER OUTPUT or through a sensor module.)
2. On the Measuring Receiver, press the blue key then press INSTR PRESET (the AUTOMATIC
OPERATION key) to preset the instrument. Key in 45.16 SPCL to turn on the RF power
calibrator. (This provides a signal for the Measuring Receiver to tune to.)
3. On the Measuring Receiver, set HP FILTER to 300
Hz
and LP FILTER to 3 kHz. Key in 2.3
SPCL to set the audio gain to minimum. Key in 0.110 SPCL to set the audio input and audio
overvoltage detector to no input and no reset. Key in 49.
S
(shift)
0
SPCL to set the voltmeter
to measure and display the audio peak detector output.
4. Adjust A5R38 (PK DET OFS) for a display between 0.0003 and 0.0007.
5. Key in 49.9 SPCL to set the voltmeter to measure and display the average detector output.
6. Set A5R2 (RECT OFS) fully ccw to shut off A5U3.
7. Adjust A5R18 (AVG OFS) for
a
display between -0.0001 and +0.0001.
5-12
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