GB
8. Examples of calculations, ... / 9. Disposal
14030069.01 12/2011 GB/D/F/E
WIKA operating instructions models TR10-W, TC10-W
16
Example: Resistance thermometer
Diameter: 6 mm
Medium temperature: T
M
= 150 °C
Supplied power: P
o
= 0.8 W
Temperature class T3 (200 °C) must not be exceeded
Thermal resistance [Rth in K/W] from table = 16 °K/W
Self-heating: 0.8 W x 16 °K/W = 12.8 °K
T
max
= T
M
+ self-heating: 150 °C + 12.8 °C = 162.8 °C
As a safety factor for type-tested devices (for T6 to T3), 5 °C must be deducted
from the 200 °C, therefore only 195 °C is allowed. Thus, in this case, the temper-
ature class T3 is not exceeded.
Additional information:
Temperature class for T3 = 200 °C
Safety factor for type-tested devices (for T6 to T3) *1 = 5 °K
Safety factor for type-tested devices (for T1 to T2) *1 = 10 °K
Safety factor for the use of the instrument Category 1 (zone 0) *2 = 80 % is not
applicable
*1 EN 60079-0 / EN 60079-1
*2 EN 60079-26
8.2 Calculation example for Version 2, thermocouple
Under the same conditions, there will be a lower value for the self-heating since
the supplied power is not only active at the sensor tip, but over the whole length
of the measuring insert.
Thermal resistance [Rth in K/W] from table = 3 °K/W
Self-heating: 0.8 W x 3 °K/W = 2.4 °K
T
max
= T
M
+ self-heating: 150 °C + 2.4 °C = 152.4 °C
As a safety factor for type-tested devices (for T6 to T3), 5 °C must be deducted
from the 200 °C, therefore only 195 °C is allowed. Thus, in this case, the temper-
ature class T3 is not exceeded.
This example clearly shows that the self-heating can be ignored.
9. Disposal
Dispose of the device components and packaging materials in accordance with
the relevant country-specific waste treatment and disposal regulations of the
region.
