Owner's manual

Calibration  4
MultiCal mmHgA/PSIA Pressure Module Manual
Calibration
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RECOMMENDED EQUIPMENT
A calibration cycle of 1 year is recommended to maintain the MultiCal within specications.
Instrument Minimum Specication
Pressure Standard ± 0.025% of Reading
Digital Voltmeter ± 0.025% of Reading with a 10MΩ input impedance
You do not need to use a reference multimeter if the MultiCal will be used with only one multimeter. In those cases, your overall accuracy may be better if it is
calibrated as a set with the matching multimeter.
Many digital voltmeters have a 10 MΩ input resistance. Your reference multimeter should have the same input impedance as the multimeter(s) the module
will be used with. In some cases this may mean that the reference multimeter will need to have its input impedance lowered.
For example, if your reference multimeter has an input impedance of ≥10,000MΩ, and the MultiCal will normally be used with a 10MΩ impedance meter,
simply connect a 10MΩ resistor in parallel with the input to the reference.
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CALIBRATION PROCEDURE
1 Connect the MultiCal to the pressure calibration system and to the multimeter. Be sure that the pressure calibration system and the connection to the
MultiCal is leak free.
2
Allow the MultiCal to stabilize at room temperature, away from drafts, for at least 30 minutes before proceeding with calibration. Turn on the multimeter
and allow it to warm up per the multimeter operating instruction. Set the multimeter to the appropriate DC volt or millivolt scale.
3 Verify the condition of the battery and replace the battery if necessary. Follow steps 1– 4 of the Battery Replacement procedure to disassemble the Multi-
Cal (do not remove the battery or reassemble the MultiCal).
4
Set the switch on the MultiCal to the mmHgA position (switch in position closest to the banana plugs). Allow the MultiCal to warm up for two minutes.
5 Apply full vacuum to the MultiCal. When the vacuum gauge indicates 10 milliTorr adjust the Fine Zero potentiometer (R1) for a reading of 0.01mV ±0.01mV.
If the zero adjustment range of the Fine Zero potentiometer is inadequate, the coarse zero must be readjusted.