Recorder Output - HP 8901B Operation And Calibration Manual

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