CALIBRATION PROCEDURE
General
In the following procedure, a test equipment setup is shown
for each major setup change. Complete control settings are
listed following the illustration. To aid in locating individual
controls which have been changed during the complete cali-
bration, the control names are printed in bold type. If only
a partial calibration is performed, start with the setup pre-
ceding the desired portion of the procedure.
NOTE
When performing a complete recalibration, best
performance will be obtained if each adjustment is
set to the exact setting, even if the Check is with-
in the allowable tolerance. The following pro-
cedure uses the equipment listed under Equipment
Required.
Preliminary Procedure
Remove the instrument from the container, connect the
autotransformer (if used) to a suitable power source, then
connect the Type 491 power cord to the autotransformer
output (or directly to the power source). Set the autotrans-
former output voltage to 115 (230) volts, check the rear panel
power selector and set to the same nominal voltage. Turn
the Type 491 power switch to on and allow at least 20
minutes warmup at 25° C, ±5° C before checking the instru-
ment to the given accuracy.
6-7
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