WIKA TR21-A Manual De Instrucciones página 5

2. Design and function
2.2 Description
The model TR21 miniature resistance thermometers consist of a temperature sensor and a
thermowell with a hygienic process connection.
Any change in the temperature causes a change in the resistance of the sensor in the
temperature sensor. This change can be measured directly or can, optionally, be converted
into a 4 ... 20 mA signal proportional to the temperature.
The thermowell is used to adapt the thermometer to the process and protects the sensor
against harsh process conditions. Furthermore, the detachable connection from the
thermowell in the TR21-A and TR21-B variants enables the removal of the temperature
sensor without having to open the process. In this way, any hygienic risk is minimised
and it is possible to calibrate the entire measuring chain (sensor, transmitter if required,
connection cable) on site, without having to disconnect the electrical connections.
Overview of the process connections, thermowell variants
Miniature resistance thermometer, model TR21-A with thermowell model TW22
■
Clamp
+
Union nut SMS
WIKA operating instructions model TR21
VARIVENT ®
Process connection, straight
BioControl ® DIN 11851/DIN 11864
Welding ball
Ball-/Collar-type
compression fitting
EN
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