Siemens SIMATIC RF600 Series System Manual page 415

Ignitions of dust-air mixtures
Using the RF640T transponder with radiant power greater than 1280 mW ERP requires
compliance with the reduced maximum ambient temperature (see diagram) for maintaining
the maximum temperature value of 135 °C.
Non-compliance with the permitted temperature ranges while using the transponder can
lead to ignitions of dust-air mixtures.
The respective temperature value and the maximum allowed ambient temperature in relation
to the radiated power of the antenna is shown in the diagram below:
Figure 7-32
SIMATIC RF600
System Manual, 11/2018, J31069-D0171-U001-A21-7618
WARNING
Temperature value
Ambient temperature
Temperature value and maximum permitted ambient temperature in relation to the
radiated power
Transponder
7.12 SIMATIC RF640T
415