Troubleshooting Chart Chapter Eight: Troubleshooting
75
MFC output signal
matches setpoint, but
actual gas flow less (as
determined by transfer
standard)
Contaminated bypass Check process chamber pressure.
Compare to normal or reference.
MFC programmed for different
gas
Compare gas programmed in MFC to
actual gas used. Verify using DNet
or Ethernet interface.
MFC cannot achieve FS
flow
Inlet pressure low Increase inlet pressure
Outlet pressure high Decrease outlet pressure
Valve contamination Check valve current for maximum
position
Gas line
blockage/contamination
Measure pressure drop across
component suspected of
contamination such as filter or check
valve
MFC setpoint in counts > than
100% FS of 24567 counts
Program attributed 6 to 100% =
24567 counts (0x6000)
Output signal matches
setpoint @ higher flows,
but will not go to 0
MFC valve partial contamination Cycle-purge device, check valve
current
Faulty control valve, adjustment
or electronics
Run MFC diagnostics, call MKS
service center
Inlet pressure too high Decrease inlet pressure
Device zero offset re-zero device with known zero flow
conditions
Display powers up, but
MFC does not respond
Bad DNet/RS485 connection Check status DNet polled
connection/RS485 connection. check
network LED
Incorrect MAC ID Address Check MAC ID on device
Incorrect baud rate setting Check baud rate on device
Incorrect DNet I/O Instance
Setting
Check I/O setting using DNet
commissioning tool/software
Check tool host
Low power, power supply Measure current & voltage from
power source
MFC output shows large
overshoot
Inlet pressure too high Decrease inlet pressure
Actual inlet pressure higher
than pressure programmed to
Adjust programmed inlet pressure
through Ethernet GUI.
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