A passive infrared sensor (PIR sensor) is an electronic sensor that measures infrared (IR) energy radiating from objects in its field of view. They are most often used in PIR-based motion detectors where the change in this energy will cause it to trigger.
- Passive Infrared Detector
- Occupancy Sensors and Security Motion Sensors are designed to work differently. They are not interchangeable. While this trouble shooting guide will assist in problems with either device, it will not solve using the wrong product in the application.
- If you are using a detector with "Pet-Immunity" read the instructions carefully. The weight rating is only a guide. The infrared heat signature of a pet with short hair is larger than the same size pet with long hair.
- Keep the PIR, at least, 3 feet from a HVAC duct and/or faced away. HVAC ducts can blow a column of air that can be mistaken as an intruder
- Be aware of glossy surfaces in the detection area. Infrared energy can be reflected off any glossy surface. Sunlight or other sources with IR can be seen by the PIR even if the heat or cold source is not within the detection area. Some surfaces will reflect less than others will. Beware of mirrors, windows, floors or counter tops with a glossy finish. For example, a PIR can detect a quick change in infrared energy if sun light comes through a window (which may not be covered by the PIR) and shines on a tile floor (which is covered by the PIR).
- Do not aim a PIR at a window. Even though the PIR cannot “see” through glass, lights from a passing car can also pass through the window at night and directly into the lens of the detector.
- Insects crawling inside or across the lens of the PIR can cause the PIR to trigger an alarm. If the detector is in an area subject to insect activity, seal the detector.
- Do not use a PIR in rooms that allow temperatures to reach 95° to 120°F. The detection performance can decrease because is will have a difficult time differentiating an intruder over the ambient temperature of the room.
- A PIR cannot see through objects. If you obstruct the view of the PIR, (curtains, screens, large pieces of furniture, plants, etc.) it may block the pattern of coverage provided by the PIR.
- Objects moving in the detection area can cause the PIR to trip. Anything that can sway or move due to air current can cause a change in infrared energy within the fields of view. HVAC ducts or drafts from doors or windows can cause this to happen. Other objects to be aware of are curtains, blinds, balloons, loose paper, plants, hanging banners or baskets, etc.
- If PIR is not mounted on a solid surface, vibrations can cause the PIR to move a little. A vibration can cause the PIR may see a change in energy.
- If a PIR is aimed directly at an entry door, the PIR may detect door movement before the door contact can initiate an entry delay. , causing the PIR to trigger an alarm. If the PIR has to be installed this way, it is recommended that the alarm control panel program set the PIR as an entry delay.
- The PIR coverage pattern is usually diagrammed in the manual. Different lenses create different patterns. The PIR creates multiple beams of protection and intrusion can only be detected in unobstructed areas covered by those beams.
- The PIR cannot detect changes in infrared energy (motion) that takes place behind walls, ceilings, floors, closed doors, glass partitions, glass doors, or windows.
- Coating or covering any part of the PIR lens or any part of the optical sensor can reduce the detection ability of the PIR.
- The PIR, like other electrical devices, are subject to component failure. The electronic components in it could fail at any time whether by defect, power surge, or other damage.
Summary provided by Steve Hoh, Worthington Senior Tech.