PIR Detector Selection Guide

Author: Brian Rhodes, Published on Apr 05, 2012

Motion sensors are a frequent source of 'false alarm' headaches in many intrusion systems. 'PIR', or 'Passive Infrared' technology have been widely deployed over many years of use, yet these sensors are still a considerable source of false alarms. In this note, we examine the major types of 'PIR' sensors, including wall mount, ceiling mount, curtain mount, describing where each type is best used, how to avoid false detections, and how to estimate pricing.

Overview of PIR function

As a basic function, PIR sensors monitor the change in infrared energy (IR) within a certain area. The 'passive' notation in the description indicates that these types of sensors do not emit or broadcast any infrared energy on their own; they simply monitor the infrared energy already present. The sensors have been built to be sensitive to subtle changes in radiated heat energy. Any object with mass gives off a certain level of energy detectable by these sensors, and when the sensor detects movement of that energy across the sensor face, it is used to trigger an alarm.

A common feature of PIR sensors are lenses with 'faceted' faces. Like an optical lens, the reception of the sensor is 'tuned' to be focused on specific areas. Notice in the image below how the PIR sensor lens is individually segmented:

Each segment is tuned to a certain sensitivity tolerance or detection range. In many cases, multiple sensors are divided up to cover broad areas. This 'coverage range' is the key criteria for selection. Many patterns and coverage ranges exist, and choosing the PIR sensor with a detection area designed to match the monitored area is key.

Major PIR types

Selection of the proper type of PIR sensor is key in reducing the risk of false alarms. These sensors are not designed to be 'universally' applied. In the following section, we describe the major types of PIR sensors and how application is affected.

  • Wall Mount
  • Ceiling Mount
  • Pet Immune
  • Curtain Sensors
  • Multiple Technology Sensors

Wall Mount: These sensors are typically used to monitor small floor areas, doorways, and hallways. The coverage range is typically configured to detect movement in a cone shaped zone immediately in front of and surrounding the sensor. Because this range is so tightly defined, the physical distance and angle of detection zone must be considered when specifying this type. 'One size' does not fit 'all'.

 

Get Video Surveillance News In Your Inbox
Get Video Surveillance News In Your Inbox

Ceiling Mount: These sensors are built to monitor broad ranges on all sides of the detector, but are not necessarily designed to be sensitive immediately underneath and close to the sensor. Mounting the sensors in the middle of large rooms is ideal, since all four sides surrounding the sensor can be covered.

 
 

Pet Immune: Especially in residential applications, house pets moving around at night can trip motion sensors. PIRs designed with 'pet immunity' or 'pet resistance' typically have the lowest detection zones adjusted to be less sensitive than other zones. In this way, low-moving small masses like animals will not exceed the tripping threshold of the sensor, but a larger human being will.

 

Curtain sensors: These PIRs are designed to detect movement in a narrow vertical band, akin to a hanging curtain. This is useful in setting up perimeter detections or boundary zones. Curtain PIRs can be set up adjacent to windows or doorways, triggered only when someone passes through.

 

Multiple technology sensors: PIRs designed with more than one IR sensor reduce false alarms since both sensors must be independently tripped to alarm. The concept behind a 'multiple technology' sensor is the same, except that two or more different types of detection sensors must be tripped. Often, 'microwave' or 'ultrasonic' type sensors are paired with PIRs to achieve this effect. These sensors might appear cosmetically similar to 'single technology' PIR sensors but they can significantly cut the risk of false alarms.

Notice in the coverage map below that two detection zones are depicted, one labeled 'Motion, IR' and the other 'Motion, Ultrasonic'.  These labels indicate the zones and sensitivity of both technologies working together in one unit.

5 Steps to Minimize False Alarms

When properly applied, PIRs will not often be a source of false alarms. However, many factors contribute to "proper application".  The 5 item checklist below covers some of the basic considerations that contribute to good PIR use:

1. Place PIRs so they are not near windows: IR interference from sunlight or headlights can cause false alarms. Strong IR sources and heat can be found within ambient light sources. 'White light filtering' is commonly designed into PIRs, and especially should be used if the sensor faces windows.

2. Avoid air exchanger registers: temperature changes will influence the sensitivity of electronics, and airborne dust can interfere with or trip detection zones.

3. Do not mount PIRs adjacent to lighting: The ambient light might not interfere with detection, especially if proper white light filter is in place, but swarming insects, interference from light ballasts, and local heat zones can blind a sensor or trigger false alarms.

4. Confirm sensor power is adequate and stable: another source of frequent false alarms is insufficient device electricity. If a particular sensor is a frequent source of false alarms and no other obvious trouble sign is present, double checking device power can reveal problems.

5. Blinded by the light: Hotspot IR illuminators, like those commonly used in video surveillance, can also blind or falsely trigger some PIRs. This type of interference is sometimes difficult to pinpoint because it is not a visual type of interference. Noting where IR illuminators are in use and masking the PIR accordingly may be necessary.

Pricing

The pricing guidlines below extend to the basic type of sensor, but more costly programmable PIRs are available. In general, unit cost increases with greater sensitivity range and longer detection zones. 

Each sensor requires a source of power, and specific mounting hardware depends on the unit purchased.

4 reports cite this report:

Bosch Blue Line Intrusion Motion Detector Tested on Jan 03, 2017
False alarms from motion sensors are one of the most aggravating parts of intrusion detection.   Bosch says their sensors are better, even...
Intrusion Motion Sensors Tutorial on Oct 04, 2016
Motion sensors are one of the most common, and most useful alarm sensors, but they also often cause problems. Many motion sensors types exist and...
Intrusion Sensor Selection guide on Jul 21, 2016
When designing intrusion systems, a number of sensor types can be selected, including: Magnetic Acceleromteter Glass Break PE/PIR/Laser...
'DIY' vs Professional Alarm Systems on Apr 18, 2012
A growing yet controversial trend in alarm systems is for people to do it themselves, installing their own alarm systems and monitoring it...
Comments : PRO Members only. Login. or Join.

Related Reports

Axis Vs. Hikvision IR PTZ Shootout on Sep 20, 2018
Hikvision has their high-end dual-sensor DarkfighterX. Axis has their high-end concealed IR Q6125-LE. Which is better? We bought both and tested...
Amazon Ring Spotlight Cam Tested on Sep 17, 2018
Amazon's Ring has released their latest camera entry, the Spotlight Cam, which we bought and tested in our Consumer IP Camera Analytics...
IP Camera Cable Labeling Guide on Sep 14, 2018
Labeling cables can save a lot of money and headaches. While it is easy to overlook, taking time to label runs during installation significantly...
Vivotek 4MP Camera Tested (FD8379-HV) on Sep 13, 2018
Next in our series of updated 4MP testing, we bought and tested Vivotek's FD8379-HV, and entry level 4MP model claiming "top-notch quality video in...
October 2018 Camera Course on Sep 13, 2018
Today is the last day to save $50 on the October 2018 Camera Course, register now. This is the only independent surveillance camera course,...
VMS Export Shootout - Avigilon, Dahua, Exacq, Genetec, Hikvision, Milestone on Sep 13, 2018
When crimes, accidents or problems occur, exporting video from one's video surveillance system is critical to proving incidents. But who does it...
Door Fundamentals For Access Control Guide on Sep 12, 2018
Assuming every door can be secured with either a maglock or an electric strike can be a painful assumption in the field. While those items can be...
Dahua Low-Cost 4MP Camera Tested (N44CL52) on Sep 10, 2018
4MP use continues to increase, especially in low-cost models, according to integrators in our 2018 Resolution Usage Statistics. We bought Dahua's...
IP Camera Cable Termination Guide on Sep 06, 2018
Terminating cables properly is critical to network performance, but it can be a tricky task with multiple steps. Fortunately, this task is easy to...
Hikvision Value Express IP Cameras Tested Poorly on Sep 05, 2018
Even lower cost Hikvision products? Their new Value Express line is marketed for applications where "budgets are limited and performance is...

Most Recent Industry Reports

Avigilon Announces AI-Powered H5 Camera Development on Sep 19, 2018
Avigilon will be showcasing "next-generation AI" at next week's ASIS GSX. In an atypical move, the company is not actually releasing these...
Favorite Request-to-Exit (RTE) Manufacturers 2018 on Sep 19, 2018
Request To Exit devices like motion sensors and lock releasing push-buttons are a part of almost every access install, but who makes the equipment...
25% China Tariffs Finalized For 2019, 10% Start Now, Includes Select Video Surveillance on Sep 18, 2018
A surprise move: In July, when the most recent tariff round was first announced, the tariffs were only scheduled for 10%. However, now, the US...
Central Stations Face Off Against NFPA On Fire Monitoring on Sep 18, 2018
Central stations are facing off against the NFPA over what they call anti-competitive language in NFPA 72, the standard that covers fire alarms....
Chinese Government Praises Hikvision Following Xi Jinping on Sep 17, 2018
The Chinese government council responsible for managing China's state-owned companies praised Hikvision’s obedience to China’s authoritarian leader...
Amazon Ring Spotlight Cam Tested on Sep 17, 2018
Amazon's Ring has released their latest camera entry, the Spotlight Cam, which we bought and tested in our Consumer IP Camera Analytics...
European Mega Security Firm Verisure Pushing Security Fog on Sep 17, 2018
The European mega security firm Verisure (Securitas Direct), with a reported 2 million customers, is pushing security fog, as shown in this BBC...
IP Camera Cable Labeling Guide on Sep 14, 2018
Labeling cables can save a lot of money and headaches. While it is easy to overlook, taking time to label runs during installation significantly...
Favorite Intercom Manufacturers 2018 on Sep 14, 2018
Intercoms are certainly increasing in popularity, driven by the integration of video and IP networking. But who is the favorite? On the one side,...

The world's leading video surveillance information source, IPVM provides the best reporting, testing and training for 10,000+ members globally. Dedicated to independent and objective information, we uniquely refuse any and all advertisements, sponsorship and consulting from manufacturers.

About | FAQ | Contact