MAINTENANCE
The RF Voltmeter is designed to give long periods of service
without maintenance when operated in accordance with these
instructions.
It is recommended, however, that the instrument
be checked occasionally using reliable standards to insure
against errors resulting from deterioration of tubes or chopper.
To make these checks, it is necessary to have a signal source
in the 200 to 500 Kc region with less than 2% distortion at
A precision electronic volt-
levels up to 3 Volts across
meter of the averaging response type, such as the Ballantine
Model 310A or 314, Hewlett Packard Model 400D or 400H, may be
used to monitor the signal source for this purpose. To insure
its accuracy, the monitoring meter should be checked at some
dynamometer type AC meter of at least 1% accuracy.
When attempting to check the voltage calibration accuracy on
art instrument having the sensitivity and bandwidth of this
RF Voltmeter, it is essential to take precautions to avoid
errors resulting from stray pick-up voltages.
(See paragraph
3.4c,d). A well shielded signal source must be used in con-
junction with coaxial connections to both the RF Voltmeter
and the standard referenced meter. Even with a well shielded
generator and associated connections, it is sometimes possible
for the reference meter to pick up stray RF signals and feed
them into the probe. Check for this condition by disconnecting
the standard meter and noting change in level.
AN/URM- 145
a
