INSTALLATION INSTRUCTION FOR PIR-75
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2824-00001
4. Field of View
The PIR-75 has a curtain-shaped field of view formed by differential detector zones for long to short range
detection. Their relative sensitivity is balanced in function of their respective range for the recommended
mounting height of 2.5 to 4.0 m. The vertical opening angle is app. 15° resulting in a detection zone
starting at app. 12 m with the PIR-75 mounted at 4.0 m height and aligned for a detection range of 75 m
(Fig. 1).
The mounting should be done in a way to allow easy horizontal and vertical alignment while giving the
required long term stability.
5. Alignment
The detection range of a PIR detector is not limited but a function of size, speed and temperature contrast
of a target against its background. The PIR-75 should be aligned so that the field of view is terminated by a
natural or artificial background at the end of the range.
Where a terminating screen is used its surface should not be glossy to avoid reflected images from outside
the field of view. Also the material may be transparent for visible light but it has to block thermal radiation;
wood, poly-carbonate and acrylic are suitable materials.
Effectiveness of a screen has to be checked by walk testing around the screen. Signals from walk tests in
front of the screen should still be strong while movements behind the screen should result in signals well
below the threshold level. If walk tests or vehicles passing behind the screen are strong enough to trigger
an alarm the PIR-75 should be tilted slightly downward. The Installation Tester IT 44 gives accurate
information about signal strengths during a test.
Coarse alignment can be done visually by looking along the grove on top of the detector. Accurate fine
alignment is easily achieved with the help of the Universal Telescopic Sight ZA P 03 which can be placed on
top of the PIR-75 for this purpose.
The graticule of the ZA P 03 corresponds to the axis of the detector. The detection curtain extends from +
0.6° to _15° in the vertical plane from the axis of the detector. Table 1 shows the elevation (Z) of the upper
edge of the field of view from the axis and the total width (Y) of the field of view as a function of the actual
distance from the PIR-75.
Table 1
Note:
The dimensions „Y“ and „Z“ are calculated figures verified by experiments. Actual dimensions
will vary with contrast conditions.
Distance X
Total width Y
Elevation Z
20 m
0.65 m
0.25 m
40 m
1.30 m
0.50 m
60 m
1.95 m
0.75 m
80 m
2.60 m
1.00 m
100 m
3.25 m
1.25 m
