7-4
GF Series
Installation and Operation Manual
X-TMF-GF Series-MFC-eng
Part Number: 541B137AAG
March, 2010
Section 7 System Troubleshooting
Symptoms & Possible Causes Corrective Action
6. Gas flow, or GF1XX pressure reading
oscillates.
Are inlet and outlet pressures stable? If outlet pressure is unstable, check for
(no oscillation or hunting) a faulty vacuum pump,
or hunting at a downstream valve.
NOTE: Most GF1XXs calibrated
with nitrogen will oscillate Check inlet pressure on tool. A faulty
with hydrogen or helium. pressure regulator can make the
GF1XX appear to oscillate.
Adjust inlet pressure up or down by 2
psig increments until hunting disappears.
Verify common gas pressure is
within range.
NOTE: Hunting or oscillation can be
contributed to multiple GF1XXs sharing
a common gas manifold. Therefore,
inspect gas delivery sources to
the gas box. (for example; two tools
sharing a common gas bottle and
calling for gas at the same time.) Valve leak.
Unregulated gas pressure from Facilities.
7. GF1XX does not read zero pressure
when gas is shut off.
Is the differential pressure across Verify that the pressure is correct for
the GF1XX really zero? the gas and range. If the GF1XX has
been contaminated, it may not be able
to close, and therefore, will not zero.
Equalize the pressure across the GF1XX by
opening it briefly. Set up the GF1XX for zeroing.
Then perform the zeroing procedure in Section 5.
Is the GF1XX configured properly Use the tool software to verify.
in the tool software?
Is the GF1XX mounted to the Refer to the side can label on the GF1XX.
proper attitude? The GF1xx should be calibrated
in the attitude it will be operating at.
8. OEM tool does not read correct GF1XX
zero reading.
Is the differential pressure across the GF1XX GF1XX valve leakage.
really zero? Incorrect MFC zero.
Is the supply voltage within specified range?
Is the GF1XX mounted in the proper attitude?
Is the flow output signal of the GF1XX
really zero?
9. Zero Drift.
Improper zero of the GF1XX? GF1XX aging or sensor stabilization.
Excessive Valve leakage? Zero is not correct.
Table 7-2 GF1XX Troubleshooting Guide (Continued)
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