Wika TR10-C Manual de usuario descargar pdf (Pagina 27)

WIKA operating instructions resistance thermometers and thermocouples, Ex n

14106886.01 06/2014 GB/D

10. Faults

Faults Causes Measures

No signal/ line breakage 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

The 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 suitable compensating cable

Display of 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

tted with a 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 shielded connecting cables, and

increase the separation from motors

and power cables

Earth circuits Eliminate potential dierences by

using galvanically isolated transmitter

power supplies 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 pressure and/or signal

are 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 11.2 “Return”.

10. Faults

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