MKS P9B, Instruction Manual, Page: 49 / 112

Analog Interface Input and Output Options Chapter Four: Analog and Digital Interface
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In order to complete a true zeroing of the device, ensure the following conditions are satisfied prior to
beginning the procedure.

Device is installed in the orientation intended for final use (i.e. horizontal base down, vertical flow up,
etc.).

Device is powered at operating temperature, preferably for 30 or more minutes.

Devices subject to ambient temperatures other than room temperature (23º C) should be zeroed under
those conditions.

Pressure drop and flow across the device is reduced to zero. Depending on the gas panel configuration,
this may be done by one of the referenced procedures. See Chapter 7 “Maintenance” for zeroing
procedures.
How To Override the Valve (Controllers Only)
The valve override feature enables the control valve to be fully opened (purged) or closed independent of the
setpoint command signal.
If the MFC is equipped with a 9-pin Type D connector:
To Open
the valve, apply 5 to 15 VDC to Pin 1.
To Close
the valve, apply -5 to -15 VDC Low to Pin 1 or connect Pin 1 to Signal Ground.
Normal Setpoint operation occurs when Pin 1 is allowed to float.
If the MFC is equipped with a 15-pin Type D connector:

To Open
the valve by applying a +5 to 15 VDC to pin 4
or
connect pin 4 to the power ground pin.

To Close
the valve by applying a -5 to 15 VDC low to pin 3
or
connect pin 3 to the power ground pin.
Priority of the Valve Commands
The MFC executes commands based on a hierarchical command structure. The highest priority command is
Valve Close, followed by Valve Open, and then Setpoint Control. Therefore, if the flow controller is
operating under Setpoint Control, you can send a Valve Open command to force the valve to the full open
position.
Note
When both the Valve Close and Valve Open pins are pulled down, the Valve Close command
takes precedence and the valve is moved to the closed position.