Model 8901B
Recorder
Output
Operation
FUNCTIONS
Special Functions 49 and
50
(Display Internal Voltages)
Voltages greater than
10
Vdc applied to the
RECORDER
OUTPUT
could
cause damage to the internal circuitry.
DESCRl
PTlON
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 RF Power measurement.
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 of 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 on a stripchart recorder)
and accuracy improvement.
Special Functions 49 and
50
are Service Special knctions which are documented more fully in
Section
8
of the
Service Manual.
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:
Recorder Output
3-87
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