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Operation
Model 8902A
PROCEDURE
When a modulation measurement is selected, a detector is automatically activated.
To obtain a peak detector, select either PEAK+ o r PEAK-. Press both keys simultaneously t o enable
the peak-average (PEAK;t/2) mode.
Peak hold is used only with the peak detectors. Selecting PEAK HOLD initiates the peak hold mode.
To initiate another peak hold, press that
key again. The display is now updated with the new peak.
The peak hold feature does not operate in the peak-average mode.
To
obtain the average-responding, rms-calibrated detector, select AVG.
To
initiate the true rms measurement, select
RMS
(Blue Key, AVG). The true rms detector is selected
automatically for the external audio level measurement (Special Function 30), audio distortion
measurement, and SINAD measurement (Special Function 29).
HP-IB PROGRAM CODES
Program
Code
I -
Function
PEAK+
PEAK-
PEAK HOLD
AVG
RMS
PEAKd2
D1
D2
D3
D4
D8
D9
COMMENTS
Input/Output Status.
The signal at MODULATION OUTPUT/AUDIO INPUT, AM OUTPUT, o r FM OUTPUT is not
affected by the DETECTOR keys.
True RMS Detector.
Only the true rms detector can be used for external audio level (Special Function 30) and f o r audio
distortion measurement, and SINAD (Special Function 29.)
HP-IB Automatic Selection of Pre-Display.
When the true rms detector is selected, the pre-display mode
f o r
FM de-emphasis is automatically
enabled. This is true whether
FM
has been selected o r not. (Selection
of
the
FM
de-emphasis time
constant, however, remains unaffected.) The pre-display mode remains enabled until deliberately
disabled. This idiosyncrasy is important to remember when programming the instrument via
HP-IB.
Peak Detector's Response Time.
A
slower response time for the audio peak detectors can be selected with Special Function 5.1.
(Refer to A iidio DcWYor Rc>.sponsc o n page 3-205.)
3-202
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