Motion sensors

[edit] Introduction

Motion, occupancy or vacancy sensors are used in a variety of situations within and around buildings, for security and lighting control as well as more continual in-use monitoring and assessment. A key specification of sensors that monitor use on a more continual basis is that they need to do so whilst maintaining the privacy of individuals and thus comply with the General Data Protection Regulations (GDPR).

Below a variety of different examples are given.

[edit] Passive infrared (PIR) sensors

Passive infrared (PIR) sensors- are small, low powered and cost effective, they sense a changes in temperature between the background and a warm heat emitting body. Everything emits low-level radiation, the pyro-electric sensor detects the differing levels of infrared radiation and thus senses movement or presence. Also called presence detectors these might be used within rooms such as offices, cubicles such as in washrooms or on the underside or desks or tables to detect occupancy.

[edit] Microwave sensors

Microwave sensors have a wider range but are more expensive, vulnerable to electrical interference and with the ability to penetrate surfaces which can cause false alarms. Continuous waves of microwave radiation or a high radio frequency are sent outwards and the reflections off an object are measured by noting the shift in frequency as the waves return.

[edit] Dual tech/hybrid

Dual tech/hybrid sensors are a combination of the above, so that both sensors need to sense changes to cause a trigger which reduces the number of false alarms, from wind movement or temperature changes etc.

[edit] People counters

People counters are a more general term for any of the above that focus on recording the number of occupants at a post or entering and leaving a space, they do so through a variety of technical means.

[edit] Time-of flight

Time-of flight sensors are similar to people counters, often using the reflection of an infrared beam on a sensor, to calculate if occupants are moving towards or away from a point, for example as an entry/exit sensor.

[edit] Infrared arrays

Infrared arrays use the same technology as described above but have greater capacity to detect directional movement within spaces and as such are able to assess how occupants might move around a building or room.

[edit] People flow sensors

People flow sensors, is a more generic term for sensors that can detect more accurately movement in a space in the same way infrared arrays can. These can monitor the real-time movement or flow of people around a space. They only detect movement, not faces, and as such are not cameras which makes them privacy and GDPR compliant.

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