Motion Detectors and REM Pods — PRN Equipment Guide

## Passive infrared motion detectors Passive infrared (PIR) motion detectors respond to changes in the infrared radiation pattern in their field of view — specifically, the movement of a warm body (people, animals) across the detector's zone. They are called "passive" because they emit nothing; they only receive. Consumer PIR sensors used in investigation are the same technology found in security lighting and burglar alarms. **What PIR sensors detect:** movement of a warm object across the detection zone. They are motion detectors, not presence detectors. A warm body standing perfectly still in view of a PIR will typically not trigger it. **Common false triggers:** small animals (mice, moths, birds), draughts that move IR-reflective materials (foil-backed insulation exposed during renovation, curtains, loose paper), direct sunlight or heating appliance moving across the zone during a timed investigation. Before treating a PIR trigger as anomalous, confirm: is the site free of rodents, birds, and insects? Is there any material in the detection zone that can move? ## Microwave and ultrasonic motion detectors Microwave detectors emit a continuous microwave signal and detect the frequency shift (Doppler effect) caused by a moving object. They can detect through non-metallic walls and materials, which makes them both sensitive and prone to triggering on movement outside the monitored space. Ultrasonic detectors work on the same Doppler principle but use ultrasound. For investigation use, PIR is generally preferred because it is more spatially bounded and easier to characterise. ## REM pods REM (Radiating EM field) pods create a small antenna that radiates a weak electromagnetic field around the device. When a conductive object — including a human hand — enters the field and disturbs it, the device triggers an alert, usually a tone or LED display. They are often marketed specifically for paranormal investigation. REM pods are essentially capacitive proximity sensors. They will respond to any conductive object that enters their field: a person's hand, a metal surface moving nearby, electromagnetic interference from radio sources, and in some cases other active electronics in the room. Their range and sensitivity can vary considerably between units, and they have not been independently calibrated for any purpose beyond detecting proximity. They are best used as broad-sweep alerts rather than precision instruments. If a REM pod triggers, the first question is always: what conductive objects or active electronics are in the vicinity? ## Combined use Deploying a PIR and a REM pod at the same location and requiring both to trigger simultaneously — or deploying a motion detector alongside audio and video recording — increases the evidentiary weight of any trigger event significantly, because it requires a simultaneous response from two independent sensors. ## Logging triggers Any motion or field trigger is only as useful as its log entry. Record: timestamp, sensor ID, location, who was present, environmental conditions, and any concurrent sensor readings. A trigger without context is noise.