Crystal MultiCal BAR/PSI - Manual (Page 2)

PN: 1763 Rev A, 4/2004
Page 2 of 7
PRESSURE is Our BUSINESS ™
Use and Operation
The internal pressure sensor measures the difference between a sealed atmospheric
reference pressure, and the pressure (or vacuum) applied to the pressure port. The pressure
being measured can be either liquid or gaseous, providing it is compatible with the materials
listed in the specification section.
CAUTION:
THE SENSOR DIAPHRAGM IS VERY THIN AND CAN BE DAMAGED OR
DESTROYED BY SOLID OR SHARP OBJECTS. NEVER INSERT ANY OBJECT
INTO THE INLET OF THE TRANSDUCER FITTING. CLEANING OF THE SENSOR
MUST BE DONE WITH APPROPRIATE SOLVENTS, ONLY.
Teflon tape or other suitable sealing compound should be used with any fitting connected to
the
1 /
8
” female NPT fitting.
Pressure Measurement
Follow this procedure to correctly use the MulitCal pressure module.
1. Plug the MultiCal into the retractile cord set and plug the cord set into the DV volts input
of the multimeter.
2. Set the multimeter to the mV (DC) range.
3. Check the battery condition: With the MultiCal still in the OFF position, the
multimeter must indicate a minumum reading of 100 mV. Readings less than 100
mV indicate the battery measurements are accurate, always check the battery condition
first, and replace the battery if necessary.
4. Turn on the MultiCal by sliding the switch to the range you intend to use.
5. “Zero” the MultiCal. With a small screwdriver adjust the small trimming potentiometer on
the end of the MultiCal until your meter reads precisely zero.
Prior to taking measurements, and recommended when changing scales, the module
should be “zeroed” at barometric pressure.
Some multimeters have a “relative” or “offset” button. This will have the same effect as
adjusting the zero knoob and accuracy of your measurements will not be degraded.
However, rezeroing the MultiCal will be required when changing scales.
Most multimeters “forget” the “relative” setting when changing from mV to any other scale,
even just to Volts. Some meters autorange from mV to Volts and then lose the “relative”
value. In these cases, the zero knob may be more convenient than the “relative” button on
the multimeter.
The zero reading may also shift when the MultiCal is shifted from a vertical to a
horizontal orientation. This is due to the oil filling that transmits the pressure signal from
the stainless diaphragm to the silicon sensor. The effect of the shift is not significant and can
be eliminated by any of the zero adjustment techniques noted above.