EN
14170746.05 03/2022 EN/DE/FR/ES
WIKA additional information model TR21 (Ex i)10
3.1 Mounting within metallic enclosures
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The case must be grounded against electromagnetic fields and electrostatic charge.
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It must not be connected separately to the equipotential bonding system.
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It is sufficient if the metallic thermowell has a solid and secured contact with the metallic
vessel or its structural components or pipelines, so long as these components are
connected to the equipotential bonding system.
3.2 Mounting within non-metallic enclosures
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Ground the cable shield at one end, preferably in the safe, and so non-Ex, area
(EN 60079-14). For instruments with cable outlet, the shield is connected to the case.
The simultaneous connection of the case and the cable shield to ground is only
permitted if any potential losses between the shield connection (e.g. at the isolated
barrier) and the case can be excluded (see EN 60079-14).
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Power the resistance thermometer via an intrinsically safe current circuit (Ex ia).
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Both the effective internal capacitance and inductance must be considered
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Fine-stranded leads with bare ends must be finished with end splices (cable
preparation)
3.3 Electrical connection
The temperature resistance of the connection lead must match the permissible operating
temperature of the cases. For ambient temperatures above 60 °C, heat-resistant
connection leads must be used (see chapter 6 “Accessories”).
3.4 Electrical connection values
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Thermometer with transmitter and output signal 4 … 20 mA (models TR21-x-xTT,
TR21-x-xTB)
Parameters Hazardous gas
atmosphere
Hazardous dust
atmosphere
Terminals + / - + / -
Voltage UiDC 30 V DC 30 V
Current li120 mA 120 mA
Power Pi800 mW 750/650/550 mW
Effective internal capacitance Ci29.7 nF 29.7 nF
Effective internal inductance Linegligible negligible
Maximum self-heating at the
sensor or thermowell tip
15 K 15 K
3. Commissioning, operation
