6. TROUBLESHOOTING
Page 143
© 2007 DH Instruments, a Fluke Company
SYMPTOM
PROBABLE CAUSE
SOLUTION
Excessive leaks in system connected to
TEST
port.
Correct leaks to extent possible. Consider
using hi volume dynamic control. 3.2.2.2,
3.4.6.2
Test volume has recently been changed
significantly.
Set pressure points and allow PPCH-G to
adapt to the new volume or run the TPCU
configuration. 5.5
Thermal pressure control (TPC) module
needs to be reconfigured.
Reconfigure TPC module after all other
possible control issues are considered. 5.5
Poor pressure control characterized
by overshooting target.
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 PPCH-G or an accessory is
dirty and causing a restriction.
Replace the filter element.
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 after recently
changing to standard dynamic
control mode.
Thermal pressure control unit (TPCU) is
initializing and causes pressure to change as
its temperature stabilizes.
Be sure PPCH-G is vented when
changing to or from standard dynamic
control mode and wait at least five
minutes after the mode change before
setting a new pressure target. 3.2.2.2
Disagreement between two Q-RPTs
in system appears excessive.
Difference is actually within tolerance and is
acceptable. 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 of 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 28
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
Incorrect pressure units and/or measurement
mode (gauge or absolute).
Set desired pressure units and/or
measurement mode. 3.3.2, 3.3.3
Q-RPT calibration coefficients have been
altered.
Check and correct calibration coefficients if
needed. 5.2, 5.2.7
Apparent inaccurate pressure
measurement/control.
AutoZ has been run and turned ON with an
incorrect standard for zero.
Check value of P
offset
. Rerun AutoZ with a
valid reference. 3.5.1
Apparent inaccurate pressure
measurement/control and
<h>
is
displayed on top line of screen.
An unplanned “head” correction is active or
head height or fluid is incorrect.
Operation is normal. Remove or change
“head” correction. 3.3.7
Q-RPT is recovering from rapid
depressurization.
Wait for Q-RPT recovery.
Pressure indication is negative.
Control mode was changed from standard
dynamic to another mode while not vented.
It is preferable to be vented when changing
measurement modes and to wait 5 minutes
while vented when changing to or from
standard dynamic control mode.
Measurement mode is absolute and
indication is absolute pressure at
atmosphere which is not zero.
Check measurement mode setting. 3.3.3
Measurement mode is gauge and AutoZ is
OFF so PPCH-G is not rezeroing.
Turn AutoZ ON. 3.5.1
PPCH-G is vented but does not
indicate zero.
Measurement mode is gauge and a head
correction is applied. When the gauge
pressure at the PPCH-G is zero, the gauge
pressure at the level of the head is not zero.
Change the head correction if desired.
3.3.7
VENT
port is plugged.
Open
VENT
port to atmosphere.
Drive air supply is too low to open vent valve.
Check drive air supply. 2.3.5
Will not vent.
Vent valve not operating.
Contact
DHI
Authorized Service Provider.
Table 28
