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