Analog Module Operation
Convectron
®
ATM Vacuum Gauge Module Instruction Manual
37
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3.8
Calibrating differential
pressure sensor zero
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
in
> 1 M
Ω
) DVM to measure the voltage across the DIAPHRAGM
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.
Figure 3-18 Differential pressure sensor zero test points and potentiometers
COMMON
test point
DIAPHRAGM ATM ZERO
ADJUST potentiometer
DIAPHRAGM ZERO
test point
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