WIKA TR10-C - Handbuch (Seite 27)

WIKA operating instructions resistance thermometers and thermocouples, Ex n
14106886.01 06/2014 GB/D
27
GB
10. Faults
Faults Causes Measures
No signal/ line breakage Mechanical load too high or
overtemperature
Replace probe or measuring insert
with a suitable design
Erroneous measured
values
Sensor drift caused by
overtemperature
Replace probe or measuring insert
with a suitable design
Sensor drift caused by chemical
attack
Use a design with thermowell
Erroneous measured
values (too low)
Entry of moisture into cable or
measuring insert
Replace probe or measuring insert
with a suitable design
Erroneous measured
values and response
times too long
Wrong mounting geometry, for
example mounting depth too deep
or heat dissipation too high
The temperature-sensitive area of the
sensor must be inside the medium,
and surfaces must be isolated
Deposits on the sensor or
thermowell
Remove deposits
Erroneous measured
values
(of thermocouples)
Parasitic voltages (thermal
voltages, galvanic voltage) or
wrong equalisation line
Use suitable compensating cable
Display of measured
value jumps
Cable break in connecting cable
or loose contact caused by
mechanical overload
Replace probe or measuring insert
with a suitable design, for example
fitted with a strain relief or a thicker
conductor cross-section
Corrosion Composition of the medium not
as expected or modified or wrong
thermowell material selected
Analyse medium and then select a
more-suitable material or replace
thermowell regularly
Signal interference Stray currents caused by electric
fields or earth loops
Use shielded connecting cables, and
increase the separation from motors
and power cables
Earth circuits Eliminate potential differences by
using galvanically isolated transmitter
power supplies or transmitters.
CAUTION!
If faults cannot be eliminated by means of the measures listed above, the instrument
must be shut down immediately, and it must be ensured that pressure and/or signal
are no longer present, and it must be prevented from being inadvertently put back into
service. In this case, contact the manufacturer.
If a return is needed, follow the instructions given in chapter 11.2 “Return”.
10. Faults