Interactive Technologies, Inc.

Paul G Saldin

Keith D Kuhnly

Robert E Brunius

A PIR sensor apparatus and method make use of a dc amplifier circuit. The dc amplifier circuit amplifies a dc-coupled sensor signal generated by a PIR sensor for analysis. For improved accuracy, the dc amplifier circuit is controlled to compensate for dc offset in the sensor signal. In this manner, the dc amplifier circuit is capable of reducing false triggering and inhibited triggering due to excessive dc offset. The amplifier is dc-coupled to an output of the PIR sensor to receive the sensor signal. A detector detects a level of dc offset within the sensor signal. A controller controls the amplifier to compensate for the detected level of dc offset The amplifier may include a differential amplifier having a first input that receives the sensor signal and a second input that receives a reference voltage. A resistor-capacitor circuit can be provided to set the reference voltage received by the second input of the amplifier. The detector and controller may be realized by a processor that detects the level of dc offset in the sensor signal, and charges the capacitor in the resistor-capacitor circuit at a duty cycle selected to adjust the reference voltage to compensate for the dc offset.

Passive infrared sensor apparatus and method with DC offset compensation

A detection system and method are capable of reducing the occurrence of false alarms and detection failures by compensating for variations in the amplitude of a detection signal generated by a PIR sensor. An adaptive threshold can be used that varies according to ambient temperature of the detection area and the frequency of the detection signal. Comparison of the detection signal to the adaptive threshold allows compensation for temperature-and/or frequency-induced variations in detection signal amplitude. The adaptive threshold can be configured for standard detection area conditions or calibrated for conditions at the installation site. Relative measurement and adaptive sampling techniques also can be used to compensate for the presence of low frequency shifts in the detection signal. Such techniques can provide an accurate representation of signal amplitude relative to a threshold amplitude despite differences in absolute signal magnitude. The use of an adaptive sampling rate that increases with the onset of a potential intruder event contributes to power conservation in the detector.

Passive infrared detection system and method with adaptive threshold and adaptive sampling

A detection system and method are capable of reducing the occurrence of false alarms and detection failures by compensating for variations in the amplitude of a detection signal generated by a PIR sensor. An adaptive threshold can be used that varies according to ambient temperature of the detection area and the frequency of the detection signal. Comparison of the detection signal to the adaptive threshold allows compensation for temperature- and/or frequency-induced variations in detection signal amplitude. The adaptive threshold can be configured for standard detection area conditions or calibrated for conditions at the installation site. Relative measurement and adaptive sampling techniques also can be used to compensate for the presence of low frequency shifts in the detection signal. Such techniques can provide an accurate representation of signal amplitude relative to a threshold amplitude despite differences in absolute signal magnitude. The use of an adaptive sampling rate that increases with the onset of a potential intruder event contributes to power conservation in the detector.

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Oakdale, MN, United States of America

Paul G Saldin