Capacitance-type material level indicator
US4555941A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 21, 1984 |
| Grant date | Dec 3, 1985 |
| Priority date | — |
| Expiry date | Sep 21, 2004 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01F23/268
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.