WIKA TR12-A Mode D'emploi page 18

6. Faults
Faults
No signal/cable break
EN
Erroneous measured
values
Erroneous measured
values (too low)
Erroneous measured
values and response
times too long
Erroneous measured
values (of thermocouples)
Temporary or sporadic
interruptions of the
measured value signal
Corrosion
Signal interference
18
Causes
Mechanical load too high or
overtemperature
Sensor drift caused by
overtemperature
Sensor drift caused by
chemical attack
Entry of moisture into cable
or measuring insert
Wrong mounting geometry,
for example mounting depth
too deep or heat dissipation
too high
Deposits on the sensor or
thermowell
Parasitic voltages (thermal
voltages, galvanic voltage) or
wrong equalisation line
Cable break in connection
cable or loose contact
caused by mechanical
overload
Composition of the medium
not as expected or modified
or wrong thermowell material
selected
Stray currents caused by
electric fields or earth circuits
Earth circuits
WIKA operating instructions models TR12, TC12
Measures
Replace probe or measuring insert
with one of a suitable design
Replace probe or measuring insert
with one of a suitable design
Use a suitable thermowell.
Replace probe or measuring insert
with one of a suitable design
The temperature-sensitive area
of the sensor must be inside the
medium, and surface measurements
must be ungrounded
Remove deposits
Use suitable compensating cable
Replace probe or measuring insert
with a suitable design, for example
equipped with a bend protection
spring or a thicker conductor cross-
section
Analyse medium and then select a
more suitable material or replace
thermowell regularly
Use shielded connection leads, and
increase the distance to motors and
power cables
Eliminate potential differences by
using galvanically isolated barriers
or transmitters