Adjustments Model 8901B
AUDIO OSCILLATOR
Adjustment
6
A2J2
RECORDER
(REAR
(FY
IN1
-
OUTPUT
PANEL1
:::::
D00000
0000
0
DlQlTAL VOLTMETER
:g;@
0
IStrp
11
INPUT
-
00
0
0 0
000000
0
0000
0
VOLTMETER OFFSET
AND
SENSITIVITY
0
Service
Sheets
14
and
16
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
..................................................................
HP 8903B
Digital Voltmeter
.................................................................
HP 3455A
HP
89018
MODULATION ANALYZER
1
I
1
i
I
I
I
I
RF
PMR
OUTPUT
(Stop
11
Figure
5-3.
Voltmeter Offset and Sensitivity Adjustment Test Setup
Procedure
1.
Connect the equipment
as
shown in Figure 5-3. Do not connect the audio oscillator
to
the
Modulation Analyzer
at
this time. (The Modulation Analyzer’s INPUT can be connected either
directly
to
the CALIBRATION RF POWER OUTPUT or through a sensor module.)
2.
On the Modulation Analyzer, 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 Modulation Analyzer
to
tune
to.)
3. On the Modulation Analyzer, 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 Adjustment 6
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