Long-range PIR detector used for detection of crawling people

The paper presents design and principle of operation of a passive IR detector of large detection range. Significant virtue of the described PIR detector is highly efficient detection of very slowly moving or crawling people. High signal-to-noise ratio was obtained by using larger number of pyroelectric sensors or by increasing number of detection zones (channels). Larger number of pyroelectric sensors forces development of a complex optical system. The presented optical system of PIR detector consists of one lens (germanium or amtir) and mirror concentrators. The optical system ensures continuity of detection zones (no "blind" area between particular detection zones). Original electronic system for PIR detector was described in which direct current amplifiers of a signal from pyroelectric sensors were applied. Electronic system automatically reduces a voltage drift from pyroelectric sensors, thus significantly decreases low limit frequency of a conduction band of amplification channel. Together with a fulfillment of this condition, low-frequency noises enhancement is observed and next detector sensitivity diminishes. To ensure large detection ranges, a new method of signals analysis was applied. PIR detector has been equipped with a channel of RS 485 standard data transmission. For registration of measurement results, special software was developed for detector diagnostics allowing registration of signals from particular detection zones. The investigation results for various ranges of PIR detector were presented. The signals from PIR detector were shown which were caused by crawling people being at the distance of 140 meters and walking, running people being at the distance more than 200 meters.