Capacitance-type material level indicator
US5048335A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 1, 1987 |
| Grant date | Sep 17, 1991 |
| Priority date | — |
| Expiry date | Oct 1, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01F25/20
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A system 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 oscillator has an output coupled to the resonant circuit and to a phase detector for detecting variations in phase angle as a funciton of probe capacitance. Level detection circuitry is responsive to an output of the phase detector and to a reference signal indicative of a 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 in a predetermined or preprogrammed manner during a calibration operation to a point indicative of the predetermined reference material level. A timer measures the duration of the automatic calibration operation for indicating conditions at the probe, such as the amount of material coated onto the probe. A reed switch is positioned adjacent to the…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.