Wika TC12-M Manual do Utilizador descarregar pdf (Página 33)

10. Maintenance and cleaning / 11. Faults

14083458.01 09/2013 GB/D

WIKA operating instructions models TR12, TC12 (Ex i) 33

10.3 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

reduce, depending on the particular application. The calibration can be carried out by the

manufacturer, as well as on site by qualied technical sta with calibration instruments.

11. Faults

Faults Causes Measures

No signal/line break Mechanical load too high or

overtemperature

Replacement of the sensor or the

measuring insert with a suitable version

Erroneous measured

values

Sensor drift caused by overtemperature Replacement of the sensor or the

measuring insert with a suitable version

Sensor drift caused by chemical attack Use of a suitable thermowell

Erroneous measured

values (too low)

Entry of moisture into cable or

measuring insert

Replacement of the sensor or the

measuring insert with a suitable version

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 ungrounded

Deposits on the sensor or thermowell

Remove deposits

Erroneous

measured values (of

thermocouples)

Parasitic voltages (thermal

voltages, galvanic voltage) or wrong

compensating cable

Use a suitable compensating cable

Indication of the

measured value jumps

Cable break in connecting cable or

loose contact caused by mechanical

overload

Replacement of the sensor or measuring

insert with a suitable design, for example

tted with strain relief or a thicker conductor

cross-section

Corrosion

Composition of the medium not

as expected or modied 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 elds

or earth loops

Use of screened connecting cables,

increase in the distance to motors and

power lines

Earth loops 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, the

instrument must be shut down immediately, and it must be ensured that signal

is 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 12.2 “Return”.

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