WIKA TR10-A - Handbuch (Seite 36)

3345267.12 01/2014 GB/D
36 WIKA operating instructions RTD and TC, intrinsically safe designs (Ex i)
GB
11. Faults
Faults Causes Measures
No signal/ line break 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
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 a suitable equalisation line
Indication of the
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
equipped 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 screened connecting cables,
increase in the distance to motors and
power lines
Earth circuits Eliminate potentials, use galvanically
isolated transmitter supply isolators or
transmitters
CAUTION!
If deficiencies cannot be eliminated by means of the measures listed above, shut
down the instrument immediately, and ensure that pressure and/or signal are no
longer present, and secure the instrument from being put back into operation
inadvertently. In this case, contact the manufacturer.
Should a return be necessary, please observe the information in chapter
12.2 “Returns”.
11. Faults