PIR or HF: choosing an occupancy sensor
Detection principle, mounting height and activity determine whether occupancy is recognised reliably.
PIR sensors respond to changes in thermal radiation within their coverage area. HF sensors transmit electromagnetic signals and evaluate changes in their reflections. Depending on the material, HF may also detect movement beyond the intended room boundary. Both technologies require selection and adjustment for the real setting.
A coverage diagram is meaningful only with its stated mounting height and movement conditions. Walking people are different from occupants making small movements at a desk. Shelves, partitions and the direction of entry influence detection too.
Test the proposed sensor during actual use. The timeout should prevent interruptions without creating unnecessarily long operating periods. Accessible manual controls and recorded settings make daily operation and later adjustments easier. The shortest possible timeout is not automatically the most useful setting.
What to clarify for your project
- Compare coverage diagrams and mounting heights.
- Test seated work and entry directions.
- Exclude unwanted detection in adjacent areas.
Remember: Test occupancy detection against the real activity.