WIKA TC12-M - Handbuch (Seite 12)

GB
3. Specifications / 4. Design and function
14083458.01 09/2013 GB/D
WIKA operating instructions models TR12, TC12 (Ex i) 12
Measuring point insulated (ungrounded) Measuring point not insulated (grounded)
Thermocouple Thermocouple Measuring point Measuring point
Sheath Sheath
Tolerance value
For the tolerance value of thermocouples, a cold junction temperature of 0 °C has been
taken as the basis. When using a compensating cable or thermocouple cable, an additional
measuring deviation must be considered.
For tolerance values and further specifications, see the corresponding WIKA data sheet
and Technical Information IN 00.23, “Application of thermocouples”.
For further important safety instructions for operation in hazardous areas, see
chapter 7 “Information on mounting and operation in hazardous areas”.
4. Design and function
4.1 Description
The model TR12-B (resistance thermometer) and model TC12-B (thermocouple) electrical
thermometers consist of a module (TR12-M, TC12-M) which is built into a housing. The
module is made up of a spring-loaded measuring insert (TR12-A, TC12-A) built into a neck
tube. The measuring insert (TR12-A, TC12-A) is replaceable.
Sensor design in TR12-A, TR12-B, TR12-M:
The measuring resistor is embedded in ceramic powder, heat-resistant potting compound,
cement compound or thermally conductive paste. A one-sided sealed tube, which is welded
to a mineral-insulated cable, forms the external shell of the sensor tip of the measuring
insert.
Sensor design in TC12-A, TC12-B, TC12-M:
The measuring insert of the thermocouple is manufactured from mineral-insulated cable.
The thermocouple consists of the internal leads of the mineral-insulated cable. The weld
spot of the thermocouple is, depending on the design, either ungrounded welded with the
sheath of the mineral-insulated cable or grounded welded.
If the temperature sensor is designed as a grounded thermocouple, the thermocouple is
joined directly to the sheath. Designs with a diameter smaller than 3 mm and with grounded
thermocouples should be considered as galvanically connected with earth potential.