WIKA TR30 - Handbuch (Seite 23)

14016442.01 06/2011 GB/D
WIKA operating instructions model TR30 per ATEX 23
GB
Example for model TR30-P-A
Resistance thermometer, diameter: 6 mm
T
amb
= 40 °C
Supplied power = 50 mW [Alternative example: 500 mW]
Temperature class for T3, Instrument Category 1
Additional information
Temperature class for T3 = 200 °C
Safety factor for type-tested instruments (for T6 to T3) 1) = 5 K
Safety factor for applications for Instrument Category 1 (Zone 0) 2) = 80 %
1) EN 50014: 1997 Section 23.4.6.1
2) EN 1127-1: 1997 Section 6.4.2
To determine: max. permissible temperature in °C at the sensor tip T
M
Thermal resistance [R
th
in K/W] from Table 4 = 75 K/W
Supplied power [P
o
in W] = 50 mW = 50 *10 -3 W = 0.05 W [0.5 W]
Self-heating [in K] = 75 K/W * 0.05 W = 3.75 K [37.5 K]
T
M
= (temperature class for T3 - safety factor for type-examined instruments) x safety factor
for applications for instrument category 1 - self-heating [in K]
T
M
= (200 °C – 5 K) x 0.8 – 3.75 K [(200 °C – 5 K) x 0.8 – 37.5 K]
T
M
= 152.25 °C [118.5 °C]
The permissible temperature in °C at the sensor tip (TM) = 152.25 °C [118.5 °C]
9. Safety-related instructions for Ex operation