Swann MALARM1301012E Manual page 6

The PIR Sensors
The Passive InfraRed (PIR) Motion Sensor will, under
typical conditions, detect a human being moving around
within approximately thirty-three feet (about 10m) from
the sensor. This is an average value, as the actual detection
range is between 16ft/5m and 50ft/15m.
As the performance of the sensor is determined primarily
by environmental conditions, no guarantees can be
offered regarding the detection range. However, the
range is typically sufficient for the majority of interior
spaces (excluding the obviously absurd, such as
basketball courts or aircraft hangars). Some garages may
be large enough that one sensor cannot cover the whole
area – we suggest testing this in the actual environment
if there's any doubt.
The sensor has a 110º field of view horizontally, and a slightly narrower view
(approximately 70º) vertically. This means that most of what you could see if you
closed one eye and put your head where you'd mount the sensor is pretty close to
the area the sensor will cover. The main blind spots, of course, are above, below or
behind the sensor itself.
Typically, the ideal placement in an environment is in the upper corner of a room,
facing slightly towards the ground (perhaps 20-25º, depending on the height of the
sensor). Try to cover typical paths through the room, focusing particularly on likely
entry and exit points. If the room has several entry points, try to cover as many of
these as practicable.
A visible PIR motion sensor can be a great deterrent to intruders – but on the other
hand, skilled intruders can avoid obviously visible sensors. Try to mix it up a bit.
How it works:
The PIR motion sensor is a passive infrared motion sensor, meaning it detects infrared
radiation rather than projecting it (unlike a security camera with infrared night vision,
which is active infrared). All objects emit this "black-body radiation" (we commonly
call it "heat") and the infrared sensor looks for any of this radiation which moves.
The PIR motion sensor is not infallible – in particular, it cannot detect objects/people
which are the same temperature as their background. So a human being moving
about on an extremely hot day might go unnoticed. Also, a security camera with
active infrared night vision in the same vicinity as the infrared sensor may give false
alarms (particularly if it is a moving PTZ system).
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