Standard / Universal automatic switch 1.1 m
–
Temperature of the heat source: surfaces at 37 °C radiate more intensely than at
10 °C(Figure 5).
–
Contrast between the heat source and the environment: if the heat source radiates just as
intensely as the environment. detection will be significantly more difficult (Figure 4).
–
Speed of movement: a faster moving object produces clearer signals in the sensor.
–
Direction of movement: if detection radiation passes tangentially, this typically results in an
abrupt sensor signal which can be evaluated well. However, if a heat source moves radial
to the sensor, the sensor signal changes happen more slowly. This makes differentiation
from the background noise significantly more difficult (Figure 5).
–
Concentration of the detection field: the number of sectors and switch segments of the de-
tection field determines the the concentration of the scan and therefore the response be-
haviour.
–
Sensor sensitivity: the sensor sensitivity can be adjusted according to application and en-
vironment. Low heat contrasts outdoors may require a high sensitivity that is far to high for
indoor use. The sensitivity should be decreased in this case.
–
Environmental medium: high humidity or rain can negatively influence the permeability for
infrared radiation.
Figure 4: Detection of heat sources – detection field geometry and distance (photometric dis-
tance law)
Figure 5: Size, insulation and contrast of heat sources
Interference sources for motion detection
In addition to the mentioned effects, other objects within the detection field could also trigger the
motion detector, e.g.:
–
Heat sources such as heating units, outlets from ventilation openings or air conditioners,
copiers, printers, coffee machines, etc. (Figure 6)
–
Draughty doorways
–
Incandescent lamps when switching on or off
–
Animals, e.g. stray cats
–
Reflections on reflecting surfaces (Figure 3)
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