Patent ID: 8319638
Filing Date: 2012-11-27
Classification: G08B

Abstract:
1. A method for detecting tampering of a motion sensor comprising the steps of: providing a lens through which energy passes; focusing the energy passing through the lens onto a single Sensing element; detecting a single voltage change in the single sensing element; filtering the voltage change by filtering out a portion of the voltage change outside of a first bandwidth, the first bandwidth including a frequency band consistent with motion detection; filtering the voltage change by filtering out a portion of the voltage change outside of a second bandwidth, the second bandwidth including a frequency band consistent with spraying on the lens and with brushing on the lens; evaluating at least one of a rate of change, duration, and amplitude of the voltage change in the first bandwidth and of the voltage change in the second bandwidth; comparing the at least one of the rate of change, the duration, and the amplitude of the voltage change in the first bandwidth with first predetermined threshold values to determine if the at least one of the rate of change, the duration, and the amplitude of the voltage change in the first bandwidth is indicative of motion and the at least one of the rate of change, the duration, and the amplitude of the voltage change in the second bandwidth with second predetermined threshold values to determine if the at least one of the rate of change, the duration, and the amplitude of the voltage change in the second bandwidth is indicative of spraying or brushing; and generating an alarm signal based upon the comparing.