MKS Stabil-Ion 370 Series, Инструкция по эксплуатации, Страница: 112 / 122

7 Service and Maintenance
7-8
Series 370 Stabil-Ion Instruction Manual - 370119
7.9 Overpressure Shutdown
As pressure increases, the ion current to the collector increases until the high density of gas molecules
begins to interfere with the ionization process. When some electrons cannot acquire sufficient energy to
ionize the gas molecules, the collector current no longer increases with increasing pressure. This
pressure is called the “turn around” pressure. Further pressure increases will result in a decreasing ion
current.
The Stabil-Ion Controller is factory set so the ion gauge will shut down when the pressure rises above the
overpressure setpoint pressures shown in Table 7-7.
For reliable operation in general applications, the overpressure shutdown point is factory set below the
Stabil-Ion Gauge turn around point at both emission currents. The overpressure shutdown can be
readjusted for specific applications according to the following procedure.
The default factory setting for this function is 100%.
1. Press the
▼
arrow key until you see the setup menu.
2. Press the SELECT key to see the units display.
3. Press the
▼
key until you see the overpressure threshold display.
4. Press the SELECT key again so that the overpressure percent is flashing.
5. Press the
▲
or
▼
arrow keys to select the desired overpressure threshold
percentage.
6. Press the SELECT key to store the new setting in memory.
Table 7-7 Overpressure Shutdown Settings.
Pressure Range Overpressure Point (Torr) % Factory Setting
H
2 x 10
-2
100
✔
H
1 x 10
-2
50
H
4 x 10
-3
20
H
2 x 10
-3
10
L
8 x 10
-4
100
✔
L
4 x 10
-4
50
L
1.6 x 10
-4
20
L
8 x 10
-5
10
Setup
Menu
UNITS
TORR
OVP. THLD
100%
OVP. THLD
100%
OVP. THLD
90%
OVP. THLD
90%