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Model 8902A
Operation
Recorder Output
FUNCTIONS
Special Functions 49 and 50 (Display Internal Voltages)
Voltages grealer fhan
10 Vdc applied
to
fhe RECORDER
OUTPUT
corrld
cairsc damagc .to
ihc
infcrnal cirmifry.
DESCRIPTION
The RECORDER OUTPUT makes available the voltage that is being read by the instrument's
internal dc voltmeter. Accuracy can be improved for some measurements by connecting to the
RECORDER OUTPUT a dc voltmeter that has greater accuracy, linearity, offset, and resolution
than the internal voltmeter. This procedure significantly improves the accuracy of the R F Power
and Tuned R F Level measurements.
In normal operation, the internal voltmeter is constantly taking readings at various points throughout
the instrument as part of its measurement process. The signal at the RECORDER OUTPUT then,
is a random series of pulses o f varying level. When Special Function 49 or 50 is not enabled, the
RECORDER OUTPUT is useful mostly as a troubleshooting aid.
However, Special Functions
49
and 50 can set the internal voltmeter to suspend normal operation
and to measure one input only. The voltmeter's input is displayed and delivered to the RECORDER
OUTPUT. This feature has two general applications: data logging (for example o n a stripchart
recorder) and accuracy improvement.
Special Functions
49
and 50 are Service Special Functions which are documented more fully in
Sccfion
( I
of the Stwicc Manrid. Use the following partial list of Special Functions to "freeze" the
instrument (no ranging, retuning, etc.) and deliver to the RECORDER OUTPUT a dc voltage equal
to the level being read by the internal dc voltmeter:
3-9
1
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