26 June 2020 - Rick Wakeham
Featured in: Product information and OPTEX tech tips, Tech Tip, Intrusion detection
When installing an external PIR or dual tech intrusion detection system, it is important to check if any elements within the detection area may generate nuisance alarms. If some have been identified, they should be masked.
What could generate nuisance alarms?
A moving tree or bush could create a contrast of temperature with the background and generate a nuisance alarm. Metallic or glass surfaces reflecting sunlight and heat such as cars can be another potential source of false alarms for outdoor motion PIR sensors. The use of dual-technology sensors, combining Passive Infrared and Microwave technologies helps reduce nuisance alarms. Even with dual tech sensors, it is best-practice to mask the identified elements.
How to mask part of the detection area?
The area to mask can be located anywhere within the detection area: on the left, the right or in the middle. The way to mask it is to block the sensor’s infrared beam covering this specific area, using masking sticker strips. The strips should be applied on the inside of the sensor’s lens, not on the outside. Sliding mechanisms on the side of the sensor and plastic masking plates are also a solution provided with our WXI and WXS 180 degree Sensors.
Our low-mount 12m external VXI or VXS sensors are delivered with masking template stickers to create different detection shapes ranging from L and V shapes to rectangular shapes. This gives a high degree of flexibility to adapt the detection area to the different sites. Read the guide to special detection area setting here.
OPTEX 180 degree low-mount PIR sensors feature a sliding shutter system which allows adjustment of the angle of detection and therefore mask the angle which covers the item likely to generate nuisance alarms. Additionally, if the area to mask is in the middle of the detection area, we provide masking plates. Click here to watch the area masking guide for WXI.
For our high mount sensors, such as the HX and QXI series, masking strips are supplied in the box. You can mask individual sections of the detection area by placing the corresponding strip on the inside of the lens. The latches that hold the lens in place can be found at the top, bottom, left and right of the lens. The lens can be removed easily by unlocking each latch with your thumb or screwdriver and gently push the lens out.
Things to avoid
The masking strips we provide are made of a specific material and cut in a particular shape to cover accurately the lens area. Don’t use any other adhesive to cover the sensor lens and certainly don’t try to spray part of the lens. This will void the warranty.
Be careful when you are masking part of the detection area that you don’t create any blind spots in vulnerable areas.