PROXIMITY DETECTION DEVICES

摘要

A proximity detection device comprises an oscillator adapted to produce a square wave oscillation, capacitive proximity sensor means whereby the self-capacitive proximity effect of an article or body to be detected modifies the rise and/or fall time of the square wave, and means for detecting the change between the two waveforms. Preferably means is provided for squaring up the modified waveform, which is then similar to the original square wave but delayed in time, and means is provided for detecting the delay between the two square waveforms. The detection device is readily adapted as a portable alarm the circuitry of which is shown in Figure 12.