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4.4
Setpoint relays
Reading pressure values
Table 4-7
Appropriate graphs and tables for reading pressure
Figure or table number, page
Figure 4-3, page 46
Figure 4-4, page 47
Figure 4-5, page 48
®
Convectron
ATM Vacuum Gauge Module Instruction Manual
The module includes four single-pole, single throw (SPST) relays. Each relay
has programmable activation and deactivation setpoints. The setpoint is a
programmable value representing an N
activates or deactivates.
• When the module is shipped from the factory, relays setpoints are out of
any acceptable operating range, and relays will not operate.
• You must configure relays to make them operable.
• After relays have been made operable, you may send an O command to
disable any specified relay.
The graphs on pages 46–48 enable you to determine the indicated N
pressure that corresponds to a specific true pressure of 10 other commonly
used process gases.
Refer to Table 4-7 to find the appropriate graph:
Pressure range in Torr
1 mTorr to 100 mTorr
100 mTorr to 1000 Torr
0.1 mTorr to 1000 Torr
Find the point at which the horizontal line representing true pressure
intercepts the vertical line representing indicated N
pressure. For example:
• in Figure 4-3, an indicated N
a true He pressure of 1.5 x 10
• In Figure 4-4, an indicated N
true Ar pressure of 700 Torr.
• In Figure 4-5, an indicated N
true Freon 22 pressure of 200 Torr.
If the gas being used is not included among those listed on pages 46–48, or
for a gas mixture, you will need to generate a calibration curve using a
gas-independent transfer standard such as a capacitance manometer.
RS–485 Module Operation
or air pressure at which the relay
2
Gases
All 12 process gases
Ar, CO
, CH
, freon 12, He, N
2
4
D
, freon 22, Kr, Ne, O
2
(nitrogen equivalent)
2
or air pressure of 10
–2
Torr corresponds to
2
–2
Torr.
or air pressure of 20 Torr corresponds to a
2
or air pressure of 6 Torr corresponds to a
2
or air
2
or air
2
N
or air
2,
2
45
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