WIKA TR12 Zusatzinformation Seite 21

5. Calculation examples for self-heating at the thermowell tip
5.2 Proof of intrinsic safety
Sensor with transmitter and barrier
ϑ
U
P
C + C
i
L + L
i
C / L = capacitance and inductance of the electrical connection lead
c c
Simplified verification of intrinsic safety for the above-mentioned combination
Measuring insert
U : DC 30 V
i
I : 550 mA
i
P ( max ) at the sensor = 1.5 W ≥
i
C : negligible
i
L : negligible
i
Upon comparing the values, it is obvious that it is permissible to connect these instruments
to one another. However, the operator must also take into account the values for
inductance and capacitance of the electrical connection leads.
WIKA additional information TR12/TC12, intrinsically safe designs (Ex i)
Hazardous area
≥ U
i o
l ≥ l
i o
≥ P
i o
≤ C C
c o
≤ L
c o
Head-mounted transmitter
≥ U : DC 6.5 V
o
≥ I : 9.3 mA
o
P : 15.2 mW
o
≤ C : 24 µF
o
≤ L : 365 mH
o
U ≥ U
i o
l ≥ l
i o
P ≥ P
i o
+ C ≤ C
i c o
L + L ≤ L
i c o
U : DC 30 V
i
I : 130 mA
i
P : 800 mW
i
C : 7.8 nF
i
L : 100 µH
i
Non-hazardous area
Isolated barrier
≥ U : DC 25.4 V
o
≥ I : 88.2 mA
o
≥ P : 560 mW
o
≤ C : 93 nF
o
≤ L : 2.7 mH
o
EN
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