초록 ▼

A system and probe for indicating the level of material in a vessel as a function of material capacitance comprising a resonant circuit including a capacitance probe adapted to be disposed in a vessel so as to be responsive to variations in capacitance as a function of material level. An rf oscillat

A system and probe for indicating the level of material in a vessel as a function of material capacitance comprising a resonant circuit including a capacitance probe adapted to be disposed in a vessel so as to be responsive to variations in capacitance as a function of material level. An rf oscillator has an output coupled to the resonant circuit and to a phase detector for detecting variations in phase angle as a function of probe capacitance. Level detection circuitry is responsive to an output of the phase detector and to a reference signal indicative of a predetermined level of material for indicating material level as a function of a difference between capacitance at the probe and the reference signal. In the preferred embodiments of the invention disclosed, an automatic calibration circuit adjusts the resonance characteristics of the parallel resonant circuit of the reference signal indicative of a predetermined reference material level.

대표청구항 ▼

A system for indicating the level of material in a vessel as a function of material capacitance comprising a parallel resonant circuit including a capacitance probe adapted to be disposed in a vessel so as to be responsive to variations in capacitance as a function of material level in said vessel,

A system for indicating the level of material in a vessel as a function of material capacitance comprising a parallel resonant circuit including a capacitance probe adapted to be disposed in a vessel so as to be responsive to variations in capacitance as a function of material level in said vessel, oscillator means having an output coupled to said resonant circuit including said capacitance probe, phase detection means responsive to variations in phase angle at said oscillator means as a function or probe capacitance and substantially independent of amplitude of said oscillator output coupled to said resonant circuit, calibration means for identifying a reference capacitance indicative of a predetermined level of material in said vessel, comparison means having a first input responsive to said phase detection means, a second input and an output responsive to a comparison between said first and second inputs, said calibration means including reference means connected to said second input and indicative of said reference capacitance, and means responsive to said comparison means for indicating material level in said vessel as a function of a difference between capacitance at said probe and said reference capacitance.