Chapter Four: Analog and Digital Interfaces Analog Interface Input and Output Options
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metered flow output signal is still provided on the standard output pin 2.
Start-Up Procedure for the Analog MFC
1. Leak test the fittings on the unit using standard helium leak check procedures. Do not proceed to the
next step until you are certain that there is no gas leakage.
2. Before connecting the cable leading to the MFC, verify all pinouts for power and signals match those
for the connector being used.
3. Plug the power supply/readout cable (MKS or customer-supplied) into the connector (either a 9-pin or
15-pin D type) located at the inlet end of the device.
4. Plug the other end of the cable into an MKS or MKS-compatible power supply/readout unit.
5. Apply power to the device. Once the device is sufficiently warmed-up, you can proceed to zero it.
See instructions in Section 7.
Warm Up Time
After installation and power connection, allow the MKS MFC to warm up for a minimum of 30 minutes.
This is to account for both warm-up of the device electronics as well as for the device to reach ambient
temperature conditions.
Zeroing the Device
Although MKS flow devices are zeroed at the factory prior to shipment, it is normal to check the zero and re-
zero them, if needed, when they are first installed on the tool.
A mass flow meter or mass flow device will provide a zero output signal under no flow gas conditions.
Zero offset from improper zeroing procedures can contribute to flow measurement inaccuracy. This is more
apparent at the lower end of the device flow range.
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.
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