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3.8
Calibrating differential
pressure sensor zero
Figure 3-18 Differential pressure sensor zero test points and potentiometers
DIAPHRAGM ATM ZERO
ADJUST potentiometer
®
Convectron
ATM Vacuum Gauge Module Instruction Manual
The differential pressure sensor is factory calibrated to produce a 4.000
VDC output at zero differential pressure. Any offset in this value may be
adjusted in the field.
An offset error is 1 Torr per 4 mV error in the analog output. For example,
if output voltage equals 4.040 V, the zero error for the differential pressure
sensor is +10 Torr. (Temperature and hysteresis stability is ±0.020 V, or
approximately 5 Torr.)
1.
Allow atmospheric and vacuum chamber pressures to achieve the
same value. This is a pressure differential of zero, which should be
represented by a 4.000 V output across the DIAPHRAGM ZERO and
COMMON test points.
2.
Refer to Figure 3-18 and use a high-precision, high-input impedance
(Z
> 1 MΩ) DVM to measure the voltage across the DIAPHRAGM
in
ZERO and COMMON test points on the module front panel.
3.
With the Convectron gauge port exposed to ambient atmospheric
pressure, use a flat-head instrument screwdriver to adjust the
DIAPHRAGM ZERO ADJUST potentiometer to 4.000 V.
DIAPHRAGM ZERO
test point
Analog Module Operation
COMMON
test point
37
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