Presence and motion sensors are often treated as interchangeable, yet they solve different technical problems. The difference lies in sensitivity, detection method and how the signal is used inside an automation strategy.
1. PIR technology
PIR sensors detect changes in infrared radiation and are excellent for corridors, circulation zones and spaces with clear line of sight. They are reliable, low-power and cost-effective, but they need visible movement across detection zones.
2. Ultrasonic technology
Ultrasonic sensors emit high-frequency waves and analyse the returned echo. They are sensitive enough to detect small movements and can react around obstacles, which makes them suitable for offices, toilets and storage rooms.
3. Practical comparison
- PIR: better for large movements and simpler applications.
- Ultrasonic: better for micro-movements and occupied spaces with partitions or corners.
- Dual technology: combines both to reduce nuisance switching and false triggering.
4. Energy optimisation
When combined with constant light control, HVAC setback modes and room logic, presence sensing can substantially reduce operating costs. In professional buildings, accurate occupancy data often matters more than the switching device itself.
Conclusion
The correct sensor is chosen from the behaviour of the space, not from square metres alone. Good automation design translates occupancy information into comfort and measurable savings.