Patent ID: 6446012
Filing Date: 2002-09-03
Classification: G08B,H03K

Abstract:
A proximity detection system for detecting the presence or level of material comprising:an oscillator that produces an output signal, the oscillator comprising a transistor having a base, an emitter and a collector, the transistor having an open and a closed loop gain and a base-emitter junction that rectifies resonant signals at the collector to produce the output signal, the oscillator further comprising negative feedback for reducing the sensitivity of the closed loop gain to variations in the transistor's open loop gain and for stabilizing the frequency of the oscillator; a sensor operatively coupled to the oscillator for varying the level of the oscillator output signal in response to electrical properties of the material; and a controller operatively coupled to the oscillator to receive the oscillator output signal and being responsive to variations of predetermined magnitudes of the amplitudes of the oscillator output signal for detecting the presence or level of the material, wherein the oscillator and the sensor have a merit factor Q, the merit factor Q decreasing as the sensor is placed in proximity to the material and wherein the amplitude of the oscillations of the oscillator will correspondingly diminish as the merit factor Q decreases, and wherein the oscillator output signal indicates the amplitude of the diminished oscillations.