CAUTION: There are live circuits inside the controller even when the power switch is in the
OFF position! Servicing and troubleshooting the controller must be performed by Qualified
Service Personnel.
10
Section 5:
WEL-PH Housing
+ Electrode OR
WEL Transmitter Housing
+
Electrode
Reading is Unstable
Step 1:
The pH reading is unstable when the pH electrode is
placed in the system water.
Remove the pH electrode from the system water and
place it in a beaker of water. Does the reading
stabilize? If yes, then proceed to
Step 2
. If no,
proceed to
Step 3
.
Step 2:
The electrode is still in the beaker of water, and the reading is stable.
Obtain a length of wire (the ends of the wire must be stripped) long enough to place
one end in the water in the beaker, and the other end in the system water.
With this length of wire connecting the beaker water to the system water, does the
reading stay stable?
If the reading does not stay stable, this can indicate a ground loop. A ground loop
could cause readings to be stuck at a high or low value. Or there is some electrical
interference in the system water, possibly from a mixer, recirculation pump, etc.
Removing power from each device and checking to see if the reading stabilizes can
help determine the source of the electrical interference.
Step 3:
The electrode is still in the beaker, and the reading is still unstable.
Power down the controller, disconnect the pH electrode shield wire from the Earth
ground stud inside the controller.
Does the reading stabilize?
If the reading stabilizes, then there is possibly some electrical noise coming in
through the controller VAC mains.
If the reading does not stay stable, then connect the controller to an alternate
supply voltage circuit. This may necessitate temporarily running an extension cord
for this test. If the reading still does not stay stable, please contact your supplier of
Walchem equipment for further instructions.
