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Model 8902A
Operation
FM Calibration
FUNCTIONS
CALIBRATE, SAVE CAL, Function
12
(FM Calibration), Special Function
17
(FM Calibration
Factor)
DESCRIPTION
The accuracy of the Measuring Receiver's FM demodulator can be checked with the internal
FM calibrator. The calibration process generates a calibration factor to compensate for the FM
measurement error (within the accuracy limits of the FM Calibrator). The calibration factor can
then be enabled
to
automatically correct the measured FM error in subsequent measurements using
the SAVE CAL key or Special Function 17. With the calibration factor enabled, FM measurements
can be made with an accuracy typically better than 0.5Yo. The calibration factor can be enabled,
disabled, or displayed at any time.
Other instruments in the HP
8901
and
8902
RF signal analyzer family can be calibrated or cross
checked with the Measuring Receiver's FM calibrator using Special Function
12.
PROCEDURE
Self-Calibration.
To determine the measurement error of the Measuring Receiver's FM demodulation circuits, first
allow at least a half-hour continuous operation before calibration, then perform the following steps:
1. Connect the CALIBRATION AM/FM OUTPUT to the R F INPUT with a
50R
cable (or a
2. Press the CALIBRATE key. After several seconds, the FM calibration factor is displayed in
O/o
The instrument displays 100.OOo/o if no error is measured. A display of 100.17% means the
FM
demodulator in the Measuring Receiver is reading 0.17% high. As long as the CALIBRATE key
light is on and the cable is connected, calibration repeats and the FM calibration factor is updated
approximately every 17 seconds.
To
turn
o f f
the calibrator, select CALIBRATE or any Measurement
key.
sensor module with an internal switch such as the HP 11722A) and select FM.
and stored (but not enabled unless already enabled).
NOTE
For optimitm accirracy, the instritmcnt shoirld hc continiroirsly opmating for
at least one haw hoirr hcfore calihration is performed. In addition, the .firsf
two FM Calihration Factors rtwiwd a f k r instrirment power-icp shoirld not he
iist'dl
t w n
if
the instriiment is alrcady warm, since the circirits in thc audio
chain may not hc.firlly sct[lt>d.
Correcting Measurements with the
FM
Calibration Factor.
Once a calibration factor has been determined, the instrument retains that value in its non-volatile
memory. This factor can be enabled to automatically correct FM measurements. The calibration
factor can also be disabled or displayed.
3-181
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