HP 8901B Operation And Calibration Manual page 191

Operation
Model 8901B
the calibrator output, the instrument will not zero properly.) The controller uses the zeroing digital-
to-analog converter (DAC) in the power meter to output a dc voltage to cancel any dc offset that may
be present at the power sensor. The zeroing process persists until the reading
is
zero, which may take
several seconds to complete.
MODULATION ANALYZER
1
- - - - - - - - - - - - _ _
T O
OTHER TUNED
r m
MEASUREMENT CIRCUITS
;ENSOR
MODULE
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I
I
I
..
INPUT
RF
ELEMENT CHOPPER DETECTOR DISPLAY
RF
POWER
SENSING
INPUI
RF Power Block Diagram
- 7
- -
MODULATION ANALYZER
- -
SENSOR MOOULE
r
TO
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OTHER
I
1 -
CIRCUITS
,
- a
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7
VOLTMETER-
SENSOR I
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RESISTOP
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IOENTIFIER
DISPLAY
r t l
I
I
RF
INPUT
J
I
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CALIBRATION
POWER
R E F
OSCILLATOR
Simplified Block Diagram
of
RF Power Calibration
3-76
RF Power