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103A - PAGE 4
CALIBRATION
Calibration is relatively easy with this gauge, since a pressure of only 10 microns Hg (10 millitor) or lower is all that
are required. It need not be known accurately as long as it is this low or lower. A good clean, dry, compound
mechanical vacuum pump can achieve this pressure if the oil is clean and fresh and the volume of the system small.
1. Check mechanical meter zero with the gauge turned off. Set to read ATM if necessary with screw adjust in
lower left center of meter
2. Turn on and allow about 30 minutes warm-up. With gauge tube at atmospheric pressure, set the trim
potentiometer in the rear marked "ATM" until the meter needle reads ATM.
3. Pump down to 10 microns Hg or lower. Allow sufficient time to outgas the tube after exposure to ATMin (2)
above. Set "ZERO" adjust trim potentiometer in the rear until the meter reads "0" pressure.
Calibration is now complete. Repeat 2 and 3 if desired for a final trim.
EXTENSION CABLES
A maximum of 12 ft extension may be used provided recalibration of the ATM and span adjustments are
accomplished. Extension cables are of the type "OMS-(length)-OFS" and are available from Hastings Instruments.
A 5 wire cable of no less than #18 wire is required. Hastings provides an extension of 12 ft.