MKS 937B - 6.9 Pressure Control Using a Valve

MKS 937B Operation Manual
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these flow rates), while when RatioM is switched to RatioA control, the automated pressure control
will start from the current flow rates, instead of the values defined by the Initial SP.
During the Ratio process control, the mass flow rates of the slave channels are all based on the real
mass flow of the master MFC channel so that the appropriate gas ratio can be maintained. If a slave
channel MFC flow rate is out the +/-20% of the target value, the flow rate indicator will turn red. No
PID control recipe is required for RatioM control.
6.9 Pressure control using a control valve
System pressure can be controlled by using either an upstream solenoid control valve on a delivery
line or a downstream throttle valve on the line to the vacuum pump. In this case, a pressure control
board must be installed in the COMM slot of the 937B controller. The system pressure can then be
controlled by the position of the control valve.
To access the valve control interface screen, you need to pressure the
Pressure
Control
button on the 937B
front panel. The pressure setup screen for 937B is shown in Figure 6-16.
6.9.1 Valve selection
Two types of valves can be connected to the 937B pressure control board:
 Voltage driven throttle valves (MKS 153D): These valve are installed on the vacuum
foreline downstream of a process chamber. Therefore, larger valve openings produce
lower chamber pressures.
 Proportional current driven valves (MKS 148J, 154A and 248A): These valves are often
installed on the delivery line of a process chamber, therefore, they are also called
upstream control valves. When these valves are used, larger valve openings produce
higher chamber pressure.
Due to the fact the different valves demand different power supplies, and involves different
control mechanism, the type of valve must be manually selected before connecting the valve
to the 937B controller.
To select the valve type, you can move the cursor to the test box on the right hand side of the
Valve Type, press
Enter
to enter edit mode for changing this parameter, then, use or
keys to select appropriate valve type, and press
Enter
again to save the value.