JUMO 902930 Wtrans Transmitter RTD Temperature Probe with Ex approval Operating Manual - Manual (Page 31)

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4 Transmitter Range
4.1 General information about radio transmission
Radio signals are electromagnetic waves. Their strength becomes weaker while traveling from
the transmitter to the receiver (this process is referred to as path attenuation). The field strength
is reduced inversely proportional in relation to the square of the distance between the transmit-
ter and receiver.
In addition to this natural range restriction, a reduced range can also be the result of the follow-
ing causes:
•
Reinforced concrete walls, metallic objects and surfaces, heat insulation, or heat protection
glass with vapor deposited metal layer reflect and absorb electromagnetic waves – the re-
sult is a radio shadow that is formed behind these objects.
• Metal pipes, chains, etc. on the transmitter case – for this reason, do not fasten any metallic
objects on the transmitter case.
• Insufficient spacing between several transmitters – for this reason maintain a minimum dis-
tance of 20 cm.
• The antenna is placed at an insufficient height – for this reason install as high as possible
above the ground with visual contact between transmitter and receiver.
The following are reference values concerning permeability of radio signals:
The range between the transmitter and the receiver is 300 m in open air and when using the
antenna wall holder for the receiver. The optimum reception can be achieved if visual contact
between the transmitter and receiver can be established.
When installing the receiver in a control cabinet behind concrete walls or concrete ceilings then
the antenna and the antenna cable along with the wall holder must be installed so that they
point in the direction of the transmitter.
Material Permeability
Wood, plaster, glass uncoated 90 to 100 %
Brickwork, press boards 65 to 95 %
Armored concrete 10 to 90 %
Metal, aluminum lamination 0 to 10 %