Am Calibration - HP 8901B Operation And Calibration Manual

Model 8901B
Operation
AM Calibration
FUNCTIONS
CALIBRATE, SAVE CAL,
95
CAL FACTOR, Special Functions 13 (AM Calibration) and 16
(AM
Calibration Factors).
DESCRIPTION
The accuracy of the Modulation Analyzer's
AM
demodulator can be checked with the internal
AM calibrator. The calibration process generates a calibration factor
to
compensate for the AM
measurement error (within the accuracy limits of the
AM Calibrator). Using the SAVE CAL key or
Special Function 16, the calibration factor can then be enabled
to
automatically correct the measured
AM error in subsequent measurements. With the calibration factor enabled, AM measurements can be
made with an accuracy typically better than
0.5%.
The calibration factor can be enabled, disabled, or
displayed
at
any time.
Other instruments in the H P 8901 and 8902
RF
signal analyzer family can be calibrated or cross
checked using Special Function
13.
PROCEDURE
Self-calibration
To determine the measurement error of the Modulation Analyzer's AM 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
RF
INPUT with a
50R
cable (or a sensor
2 . Select CALIBRATE. After several seconds, the AM calibration factor is displayed in
%
and stored
The instrument displays 100.00% if no error is measured. A display of 100.17% means the AM
demodulator in the Modulation Analyzer is reading 0.17% high. As long as the CALIBRATE
key light is on and the cable is connected, calibration repeats and the AM calibration factor is
updated approximately every 17 seconds. To turn
off
the calibrator, select CALIBRATE or any
Measurement key.
module with an internal switch such as the HP 11722A) and select AM.
(but not enabled unless already enabled).
NOTE
For optimum accuracy, the instrument should be continuously operating for
at least one half hour before calibration
is
performed. In addition, the first
two
AM Calibration Factors received after instrument power-up should not
be used even if the instrument
is
already warm, since the circuits
in
the
audio chain may not be fully settled.
Correcting Measurements with the AM Calibration Factor. Once a calibration factor has been
determined, the instrument retains that value in its non-volatile memory. This factor may be enabled
to automatically correct AM measurements. The calibration factor can
also
be disabled or displayed.
Selecting
5 %
CAL FACTOR or 16.2 SPCL displays the calibration factor being used.
AM Calibration
3-141