HELIX GRANVILLE-PHILLIPS Convectron ATM, Инструкция по эксплуатации, Страница: 53 / 98

RS–485 Module Operation
Convectron
®
ATM Vacuum Gauge Module Instruction Manual
45
Be
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You Beg
in
In
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A
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log O
per
atio
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R
S–48
5 Op
er
ation
M
ain
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4.4 Setpoint relays
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
2
or air pressure at which the relay
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.
Reading pressure values
The graphs on pages 46–48 enable you to determine the indicated N
2
or air
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:
Find the point at which the horizontal line representing true pressure
intercepts the vertical line representing indicated N
2
(nitrogen equivalent)
pressure. For example:
• in Figure 4-3, an indicated N
2
or air pressure of 10 –2 Torr corresponds to
a true He pressure of 1.5 x 10
–2
Torr.
• In Figure 4-4, an indicated N
2
or air pressure of 20 Torr corresponds to a
true Ar pressure of 700 Torr.
• In Figure 4-5, an indicated N
2
or air pressure of 6 Torr corresponds to a
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.
Table 4-7 Appropriate graphs and tables for reading pressure
Figure or table number, page Pressure range in Torr Gases
Figure 4-3, page 46 1 mTorr to 100 mTorr All 12 process gases
Figure 4-4, page 47 100 mTorr to 1000 Torr Ar, CO
2
, CH
4
, freon 12, He, N
2
or air
Figure 4-5, page 48 0.1 mTorr to 1000 Torr D
2
, freon 22, Kr, Ne, O
2,
N
2
or air