PIR-045
PASSIVE INFRARED DETECTOR
2800-00006 Page 4 of 10
Adaptive Threshold Discrimination (ATD)
The background noise is constantly averaged and used to adjust the threshold levels for the alarm. This special feature is
reducing the probability of nuisance alarms caused by wind, moving vegeta tion or objects that have a thermal contrast
although usually weaker than a person.
Each signal exceeding a certain minimum value will activate the ATD and increase the threshold levels depending on its
strength. The time constants for increase and decrease are chosen in a way to adapt to gradual changes. Signals generated
by a person moving within the specified speed range, however, are fast enough for detection.
Repeated movement of any kind within the field of view is therefore activating the ATD, reducing the overall sensitivity. This
has to be noted particularly when walk testing the PIR-045 following installation.
The
DIP – Switch 3
is used to activate or deactivate the
ATD
(Adaptive Threshold Discrimination), for details of the ATD
function see below.
*) Operation of the PIR-045 in this mode is possible but not recommended in outdoor applications as the nuisance alarm
rate could increase significantly as a result of turbulences.
The
DIP – Switch 4
has no function in this detector model.
Alarm Time
Alarm time and count per event is determined by the duration of the detected event and depends on the shape and amplitude
of the alarm signal. Individual alarm pulses have a minimum time of app. 2.0 s.
Internal Temperature Compensation
The PIR-045 is detecting radiation differences of a target against its background. In the course of the day and year the
contrast of a person will vary considerably and affect the signal strength. To compensate for this contrast variation, the PIR-
045 has internal temperature compensation with maximum sensitivity at app. 30°C (where the contrast of a human target is
weakest) and gradual reduction at higher and lower temperatures.
•
When installing a unit the internal temperature may take up to 30 minutes or more to stabilise to the actual external
temperature. Sufficient time should be given to the PIR-045 to reach the correct internal temperature and sensitivity
before performing walk tests.
During the initial period of operation it is strongly recommended that walk tests are repeated and signals monitored under
various weather conditions such as high and low temperatures, wind fog, snow, rain etc. to obtain comparative data and
information on the effects of environmental conditions on detection and nuisance alarm probabilities for this particular site.
Fine-tuning of the detector based on this data by changing the sensitivity settings may optimise the performance.
Switch 3
ATD
off
„off“
*)
on
„on“
