WIKA TR25 - Handbuch (Seite 24)

14073045.01 10/2013 GB/D
24 WIKA operating instructions model TR25 (Ex i)
GB
10.3 Calibration, Recalibration
It is recommended that the measuring insert is recalibrated at regular intervals of
approx. 24 months. This period can reduce, 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.
11. Faults
Faults Causes Measures
No signal/
line break
Mechanical load too high or
overtemperature
Replacement of the resistance thermometer
Erroneous measured
values
Sensor drift caused by
overtemperature
Replacement of the resistance thermometer
Erroneous measured
values (too low)
Entry of moisture into cable Replacement of the resistance thermometer
Erroneous measured
values and response
times too long
Wrong mounting geometry or heat
dissipation too high
The temperature-sensitive area of the
sensor must be inside the medium. Beware
of the mounting position of the sensor!
Deposits within the thermowell Remove deposits
Indication of the
measured value jumps
Cable break in connecting cable
or loose contact caused by
mechanical overload
Check the supply cable
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 of screened connecting cables,
increase in the distance to motors and
power lines
Earth circuits Elimination of potentials, use of galvanically
isolated transmitter supply isolators or
transmitters
CAUTION!
If faults 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, follow the instructions given in chapter 12.2 “Return”.
10. Maintenance and cleaning / 11. Faults