4.9.2 Establish a Proper “No Flow” Condition Across the MFC Control Valve The definition of a “no flow” condition is that the pressure on the inlet side of the MFC is equal to the pressure on the outlet side of the MFC control valve. Whether the MFC is at atmospheric pressure, vacuum pressure, or process pressure, the zero should not be initiated until the pressure differential across the MFC is zero. NOTE MKS recommends that an MFC be zeroed at its operating inlet gas pressure. To successfully complete the recommended procedures, a positive shut off valve should be installed in the gas line to properly isolate the MFC at operating pressures. 1. Pressurize the gas line to the inlet of the MFC (open upstream positive shut off valve if required). 2. Open the downstream shut off valve and give the MFC a full scale set point. 3. Let the MFC operate at full scale flow for 15 seconds and then close the downstream shut off valve while leaving the set point on the MFc 4. Allow the reported flow to fall to a stable zero value. NOTE The set point and flow signals can be monitored in real time on the plot page to confirm that the MFC has reached a stable zero condition. 5. If a positive shut off valve is installed upstream, close the valve and then give a zero set point to the MFC to close the control valve. 6. Issue a zero function to the MFC by holding down the button on the top of the enclosure for 3 seconds. NOTE The zero function can be also executed from the Configuration page of the web browser (see Appendix B). Digital protocols such as DeviceNet, Profibus, RS485, Ethercat, and Modbus also support zero commands that can be sent over the primary I/O (see I/O supplemental documentation for details).

Model #:GE50A013103MAV020 Serial #: 23689163 OrigConfig: N2-1000sccm IP:192.168.2.13 <\br> Model #:GE50A008103MAV020 Serial #: 23598846 OrigConfig: Air-1000sccm IP:192.168.2.14