Calibration, Recalibration; Faults - WIKA TR Manual De Instrucciones

8. Faults

7.3 Calibration, Recalibration

It is recommended that the measuring insert is recalibrated at regular intervals (resistance
thermometers: approx. 24 months, thermocouples: approx. 12 months). This period can be
reduced, depending on the particular application. The calibration can be carried out by the
manufacturer, as well as on site by qualified technical staff with calibration instruments.
8. Faults
Faults
No signal/line breakage
Erroneous measured values Sensor drift caused by
Erroneous measured values
(too low)
Erroneous measured values
and response times too long
Erroneous measured values
(of thermocouples)
Indication of the measured
value jumps
Corrosion
Signal interference
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.
If a return is needed, please follow the instructions see chapter 9.2 "Return".
WIKA operating instructions resistance thermometers, thermocouples
Causes
Mechanical load too high or
overtemperature
overtemperature
Sensor drift caused by chemical attack Use a design with thermowell
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 connecting 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 loops
Earth circuits
Measures
Replace probe or measuring insert
with a suitable design
Replace probe or measuring insert
with a suitable design
Replace probe or measuring insert
with a suitable design
The temperature-sensitive area of the
sensor must be inside the medium,
and surfaces must be isolated.
Remove deposits
Use a suitable equalisation line
Replace probe or measuring insert
with a suitable design, for example
equipped with a strain relief or a
thicker conductor cross-section
Analyse medium and then select a
more-suitable material or replace
thermowell regularly
Use of screened connecting cables,
increase in the distance to motors and
power lines
Elimination of potentials, use of
galvanically isolated transmitter supply
isolators or transmitters
EN
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