HELIX GRANVILLE-PHILLIPS Convectron ATM, Инструкция по эксплуатации, Страница: 57 / 98

RS–485 Module Operation
Convectron
®
ATM Vacuum Gauge Module Instruction Manual
49
Be
for
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You Beg
in
In
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A
na
log O
per
atio
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R
S–48
5 Op
er
ation
M
ain
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Adjusting setpoints
If the module will measure the pressure of any process gas other than N
2
or
air, you must adjust setpoints for the process gas that will be used.
If the module will measure the pressure of a gas other than N
2
or air, you
must adjust setpoints for the process gas. The true pressure of a gas other
than N
2
or air may be substantially different from the pressure that the
output indicates. For example, outputs might indicate a pressure of 10 Torr
for argon, although the true pressure of the argon is 250 Torr. Such a
substantial difference between indicated pressure and true pressure can
cause overpressurization resulting in an explosion.
1. Make sure the module is properly installed and the axis is horizontal.
(See page 8.)
2. Figure 4-3, Figure 4-4, and Figure 4-5 on pages 46–48 are graphs that
show true pressure versus indicated pressure for 12 commonly used
process gases, including N
2
and air. Refer to Table 4-8 to find the
appropriate graph:
3. Refer to the following example process control (PC) command
sequence to program
indicated pressures at which the relay will
activate and deactivate:
The example PC command sequence causes relay 1 to deactivate
when
indicated vacuum chamber pressure increases to 2.00 x 10
–1
Torr and to activate when indicated vacuum chamber pressure
decreases to 1.01 x 10
–1
Torr.
WARNING
Failure to use accurate pressure conversion data for N
2
or air to other gases can cause an explosion due to
overpressurization.
If the module will measure any gas other than N
2
or air, before
connecting relays to system control devices, adjust setpoints for
the process gas that will be used.
Table 4-8 Appropriate true pressure versus indicated pressure graphs
Figure number, page Pressure range in Torr Gases
Figure 4-3, page 46 1 x 10
–4
to 1 x 10
–1
Torr All 12 common gases
Figure 4-4, page 47 1 x 10
–1
to 1 x 1000 Torr Ar, CO
2
, CH
4
, Freon 12, He
Figure 4-5, page 48 1 x 10
–1
to 1 x 1000 Torr D
2
, Freon 22, Kr, Ne, O
2