What is PIR?

PIR stands for Passive Infrared. A passive infrared Sensor is an electronic device that measures infrared (IR) light radiating from objects in its field of view. PIR sensors are most commonly used in PIR alarms, or, in other words, PIR-based motion detectors.

Every object above absolute zero emits heat energy as infrared radiation. A PIR sensor contains a (Fresnel) lens divided into multiple zones. When a warm object moves across those zones, the thermal pattern changes and the detector triggers. The word “passive” means the sensor emits no energy of its own — it only receives.
PIR sensors do not detect heat as a temperature measurement. They detect movement of a heat source across their detection zones. A person standing completely still in front of a PIR sensor will often not trigger it.

A PIR motion sensor detects moving heat sources within a defined area. People and large animals are detected; small creatures such as insects and spiders are not. The sensor’s range, angle, and sensitivity vary between products — indoor units typically cover a wide angle at short range, while outdoor detectors are engineered for longer distances and higher resistance to environmental interference.
For indoor use, the Mobeye MiniPir iCM41 is a compact battery-powered PIR alarm with built-in GSM. For demanding outdoor environments, the Mobeye Outdoor Alarm CMVXI-R uses dual-layer detection to significantly reduce false triggers.

Any moving heat source can trigger a PIR alarm — not just intruders. Draughts, direct sunlight, reflections off dark surfaces such as black leather, and swaying vegetation are common causes of false alarms.
To minimise false triggers:
– Position the sensor away from windows and heating vents
– Avoid pointing the detector towards areas with direct sun exposure
– Adjust the sensitivity setting if your device supports it
– For outdoor installation, choose a detector with animal-filtering technology

The Mobeye CMVXI-R Outdoor Alarm addresses this with two independent detection patterns that must both trigger simultaneously to activate the alarm. This makes it highly resistant to false alarms caused by birds, cats, dogs, and small animals, which rarely cross both the upper and lower detection zones at the same time.

Digital Double Layer Detection requires both an upper and lower detection zone to be crossed simultaneously before an alarm is raised. Two internal PIR sensors independently analyse the detection, filtering out coincidental events. This is particularly effective at eliminating false alarms triggered by smaller animals on the premises.
The Mobeye CMVXI-R is also equipped with SMDA (digitally enhanced signal recognition logic), which improves resistance to environmental noise including climate changes and vegetation movement — making it well suited to outdoor and construction site security.