Chapter 3
34
Convectron
®
ATM Vacuum Gauge Module Instruction Manual
3.4
Reading relay status
Use the setpoint indicators, illustrated in Figure 3-15, to read
activation/deactivation status of relays.
• The ON indicator is green when the module power supply is ON.
• The SETPOINT1 indicator is green when relay 1 is activated.
• The SETPOINT2 indicator is green when relay 2 is activated.
Figure 3-15 Power ON and setpoint indicators
3.5
Calibrating Convectron
gauge at atmospheric
pressure
An atmospheric pressure calibration is performed on the Convectron gauge,
using N
2
, at the factory before the module is shipped. The factory
calibration sets the atmospheric calibration point for N
2
to 760 Torr of N
2
.
Because performance varies depending on the process gas, you may wish
to reset the atmospheric calibration point if a gas other than N
2
or air is
being used. Periodic resets of the atmospheric calibration point also
improve the accuracy and repeatability of the Convectron gauge near
atmospheric pressure, even if the process gas is N
2
or air.
Regardless of the process gas that is being used, you should always use N
2
or air to calibrate the Convectron gauge at atmospheric pressure.
1.
Shut off the pump and, using N
2
or air, allow the vacuum chamber
pressure to increase to the value at which the atmospheric pressure
point will be set.
2.
Refer to Figure 3-16 and use a high-precision, high-input impedance
(Z
in
> 1 M
Ω
) DVM to measure the voltage across the CONVECTRON
ANALOG and COMMON test points on the module front panel.
3.
Use a flat-head instrument screwdriver to adjust the CONVECTRON
ADJUST ATM potentiometer to a voltage that corresponds to the
atmospheric pressure at your location. Table 3-7 on page 35 lists
typical atmospheric pressure at altitude/Torr/voltage relationships.
Setpoint indicators
Power ON indicator
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