LTH MOD53, Operation Manual

Page: 78 / 110

15 Fault Finding
77
Relays Appear to Malfunction
♦
Check that the unit is “On-Line”
♦
Check that the set point configuration is correct
♦
If the relays are vibrating or “chattering” as they pass the set point, check the
hysteresis setting and increase if necessary.
♦
Ensure that the relays are connected properly and that the voltage/current
levels are not exceeding the specification
♦
Check that the instrument input cables are not picking up excessive noise,
A Bell Symbol is Flashing on the Display
The system has detected an error but the error messages have been disabled in
the “
Configuration ” menu. Enable the error messages, correct the error and then
disable the error messages only if absolutely necessary.
OE15 DO Probe Maintenance
In order to achieve the maximum reliability from the overall system the sensor will
require regular calibration and maintenance. The period for this will depend upon
the application; e.g. in aeration tanks, a weekly check on calibration and fouling
would be a reasonable estimate, for rivers a longer period, and in ditches it may
need to be more frequent. The zero check in Sodium Sulphite would be less
frequent, probably once a month.
The OE15 electrode incorporates a number of features to simplify maintenance.
The electrolyte contained within the cartridge is gelled and sealed. The cartridge is
detachable. It can be removed by undoing the large stainless steel bolt at the
bottom of the electrode.
Due to the Galvanic action of the sensor, the cartridge has a finite life. It will
provide at least 12 months of continuous use before replacement becomes
necessary. LTH Electronics operates an exchange service for electrodes, but we
recommend the purchase of a spare cartridge if the process being monitored is
continuous. The electrode should contain a weak solution of Sodium Sulphite,
which absorbs any residual oxygen in the probe and conditions the electrode for
immediate use.