Capacitance-type material level indicator
US4624139A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 21, 1984 |
| Grant date | Nov 25, 1986 |
| Priority date | — |
| Expiry date | Sep 21, 2004 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01F23/266
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A system for indicating level of material in a vessel as a function of material capacitance comprising a bridge circuit which includes 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 adjacent bridge arm includes a plurality of capacitors coupled to controlled electronic switches for selective connection into the bridge circuit. The bridge circuit is powered by an rf oscillator, and a differential amplifier is connected across the bridge circuit for detecting the balance condition of the bridge. An automatic calibration circuit includes a digital counter having outputs connected to the electronic switches. A comparator is responsive to the differential amplifier for enabling operation of the counter during a calibration mode of operation for selectively connecting the fixed capacitors into the bridge circuit until a preselected balance condition, corresponding to a preselected reference material level, is obtained. Thereafter, the differential amplifier is responsive to variation of probe capacitance from the reference level to indicate material level.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.