HP 8902A Quick Reference Manual page 324

Operation
Model .8902A
MEASUREMENT TECHNIQUE
When FM is selected and CALIBRATE is selected, a 10.1 MHz voltage controlled oscillator (VCO)
within the calibrator is driven to one end of its nominal tuning range. The frequency
of
the VCO
is counted, and the oscillator is driven to the opposite end of its tuning range where it is counted
again. The peak FM deviation is computed from these measurements.
While the VCO is at one end of its range, the residual FM of the calibrator (very low) and the
FM Demodulator (more significant) are characterized and weighted. (Refer to Residual
N o i s e
EJkts
on page 3-219.) The VCO is frequency modulated by a 10 kHz modulation oscillator, and the FM
demodulator makes another FM measurement. (Both peak detectors are used and the average is
computed.)
The Measuring Receiver compares the deviation (static measurements) with the demodulated FM
(toggled measurements) and computes its accuracy error as follows:
x 100
Demodulated FM
-
Demodulated Residual F M
Computed FM
FM Calibration Factor
(%)
=
All segments
of
the calibration are carefi~lly monitored. If any segment is out of limits, the calibration
is aborted and Error 08 is displayed.
OUTPUT
A M
~ U F F E R CALIERATOR
10.1 MHz CALIBRATION
CONTROLLED VOLTAGE
w - p
1 - 1
OUTPUT
OS
CI
L LAT 0 R
COUNTER
COUNTER AN0 OISPLAY
BUFFER CONTROLLER
COUNTER
AN0 OISPLAY
q - 1
C L E R
BUFFER CONTROLLER
I
COMMENTS
Default Calibration Factor.
If t.he instrument's non-volatile memory
is
erased, 100.00% is used as the default calibration factor.
Updating the FM Calibration Factor.
Whenever FM calibration is performed, the instrument updates the stored FM calibration factor.
3-
184