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O&M Manual
Rev-K (11/18)
Part 10 – Troubleshooting
10.1 General
The information included in this section is intended to be used in an attempt to quickly resolve an
operational problem with the system. During any troubleshooting process, it will save the most
time if the operator can first determine if the problem is related to the analyzer, sensor, or some
external source. Therefore, this section is organized from the approach of excluding any likely
external sources, isolating the analyzer, and finally isolating the sensor. If these procedures still
do not resolve the operational problems, any results the operator may have noted here will be
very helpful when discussing the problem with the factory technical support group.
10.2 External Sources of Problems
To begin this process, review the connections of the system to all external connections.
1. Verify the analyzer is earth grounded. For all configurations of the analyzer, an earth ground
connection MUST be present for the shielding systems in the electronics to be active.
Grounded conduit provides no earth connection to the plastic enclosure, so an earth ground
wiring connection must be made at the power input terminal strip. Verify metal shield is
present over incoming power connections. This shield is for safety purposes, but also blocks
electrical spikes from relay and power wiring.
2. Verify the proper power input is present (90-260 VAC or 12-24 VDC).
3. Verify the loads on any 4-20 mA outputs do not exceed the limits in the Instrument
Specifications. During troubleshooting, it is many times helpful to disconnect all these
outputs and place wire-shorts across the terminals in the instrument to isolate the system and
evaluate any problems which may be coming down the analog output connections.
4. Do not run sensor cables or analog output wiring in the same conduits as power wiring. If low
voltage signal cables must come near power wiring, cross them at 90° to minimize coupling.
If rigid conduit has been run directly to the Q46 enclosure, check for signs that moisture has
followed conduit into the enclosure.
5. Check for ground loops. Although the membrane sensor is electrically isolated from the
process water, high frequency sources of electrical noise may still cause erratic behavior in
extreme conditions. If readings are very erratic after wiring has been checked, check for a
possible AC ground loop by temporarily disconnecting feed and drain lines from the flow cell
while there is still water on the inside. The reading should be initially stable and then fall very
slowly in a smooth fashion as chlorine is depleted in the static sample.
6. Check the load that is connected to the relay contacts. Verify the load is within the contact
rating of the relays. Relay contacts which have been used for higher power AC current loads
may become unsuitable for very low signal DC loads later on because a small amount of
pitting can form on the contacts. If the load is highly inductive (solenoids, motor starters,
large aux relays), note that the contact rating will be de-rated to a lower level. Also, due to
the large amount of energy present in circuits driving these types of loads when they are
switched on an off, the relay wiring placement can result in electrical interference for other
