946 Controller Instruction Manual
pg. 61
A1
A2
B1
B2
C1
C2
FC
210.3
39.99
1.50
160.01
FC
FC
CM
10.07
CM
269.9
FC
4.0E+2
SCCM
Close
SCCM
80.0%
SCCM
SP
SCCM
20.0%
75%
V
a
l
v
e
P
o
s
Torr
Manual
Figure 6-23 946 Display with a Pressure Control Module Installed
The position displayed on the front panel for an upstream solenoid valve is actually the
percent of the full scale driving current of the valve, not the true opening position of the valve.
Note that 20-40% of the full scale driving current is often required to overcome the sealing force
and open the valve and is then the minimum indicated opening position.
6.8.1 Valve Type Selection
Following is list of valves that can be operated by the 946 controller:
•
Valves (MKS 153/T3B): This valve is installed on the vacuum pumping line of a process
chamber (also called downstream control valve). With these valves, larger valve openings
produce lower chamber pressures.
•
MKS 148, 154 and 248: These proportional current driven valves are often installed on the
delivery line of a process chamber, and are also called upstream control valves. With these
valves, larger valve openings produce higher chamber pressure.
When an upstream valve is used to control the vacuum system pressure, the valve inlet
pressure should be regulated to ensure stable pressure control. If the control system pressure is
low (say, below 10
-4
Torr), the inlet pressure should be regulated at a similar pressure range, or a
small leak valve (orifice) should be installed to avoid a pressure burst during the control,
especially if a CC or HC sensor is used.
See Figure 6-24 and use following steps below for setting the valve type on a 946 vacuum system
controller:
1. Press
System
Setup
key on the front panel to display the system setup screen as shown in Figure
6-24;
2. Move the cursor with the
or
keys to highlight Valve Type parameter;
3. Press
Enter
key to enter the edit mode;
4. Select appropriate valve type and press
Enter
again to save the setting.