DH Instruments PPC4, Operation And Maintenance Manual

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8. TROUBLESHOOTING
Page 209 © 2009 DH Instruments, a Fluke Company
SYMPTOM PROBABLE CAUSE SOLUTION
Poor pressure control characterized
by excessive overshooting/
undershooting and/or “hunting”
around target.
There is a restriction in the test connection
between the PPC4 and the test or the PPC4,
the RPM4 and the test. Restrictions are
particularly problematic at low absolute
pressures.
Remove the restriction to allow free flow
between the PPC4, the RPM4 (if present)
and the test. 2.3.7
Pneumatic control module needs to be
reconfigured. Reconfigure control module after all other
possible control issues are considered. 7.5
The volume connected to the TEST(+) port
is too small.
Add volume to the system connected to the
TEST(+) port. 1.2.3
A filter in the PPC4, the SPLT or an
accessory is dirty and causing a restriction.
Clean and dry or replace the filter element.
Excessive leak present in system.
Correct internal or external leak or increase
hold limit. 3.2.18, 3.2.13
Test volume too small.
Increase test volume. Consider use of
DVU (Dual Volume Unit) if Q-RPT is
G15K or BG15K. Consider
reconfiguration of pneumatic module
after all other possible control issues
have been evaluated. 2.3.7.2, 7.5
Poor pressure control characterized
by minor overshooting. Some overshooting is part of normal
operation to speed up pressure stabilization.
Check whether overshooting is within normal
limits. Objectively evaluate significance of
overshoot relative to UUT span and
specifications. Increase test volume.
Poor pressure control characterized
by very slow slew rate. Test volume is too large. Severe restriction
in a test line.
Reduce test volume if slew rate is
unacceptable. Remove restrictions in
line connected to
TEST(+) port.
Poor pressure control. Unstable or incorrect pressure supply.
Connect regulated pressure supply set to cor-
rect supply pressure to SUPPLY port. 2.3.4
Poor pressure control and
measurement. The PPC4 and/or the connection to the test
system are contaminated with liquids.
Purge and clean affected systems. Consider
use of Self-Purging Liquid Trap. Contact
DHI Authorized Service Provider if PPC4
is contaminated internally. 2.3.7.1, Table
36
Disagreement between two Q-RPTs
in system appears excessive.
Difference is actually within tolerance and
acceptable disagreement. Note the Internal,
Hi transducer may be a utility sensor which
has a much wider tolerance than a Q-RPT.
Compare differences observed to
tolerances on Q-RPT and/or utility sensor
measurements. 1.2.2.1, 1.2.2.2
Apparent inaccurate pressure control/
measure and little or no response
from Q-RPT or utility sensor:
Reference transducer destroyed by
overpressure. Contact DHI Authorized Service Provider.
Table 36
Apparent inaccurate pressure
control/measure when using
Internal, Hi (IH) RPT.
The IH transducer is a utility sensor, not a Q-RPT.
Operation is normal for lower specifications
of utility sensor. 1.2.2.2
Apparent inaccurate pressure
measurement/control.
Incorrect pressure units and/or
measurement mode (gauge or absolute).
Set desired pressure units and/or
measurement mode. Consider reference
temperature if unit is xxH2O. 3.2.10, 3.2.11
Q-RPT calibration coefficients have been
altered. Check and correct calibration coefficients if
needed. 7.2
AutoZ has been run and turned ON with an
incorrect standard for zero. Check value of P
offset
. Rerun AutoZ with a
valid reference. 3.2.22
Apparent inaccurate pressure
measurement/control and
<h> is
displayed on top line of screen.
An unplanned “head” correction is active or
head height or gas is incorrect. Operation is normal. Remove or change
“head” correction. 3.2.16