Two-wire level measuring instrument
US4851831A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 29, 1984 |
| Grant date | Jul 25, 1989 |
| Priority date | — |
| Expiry date | May 29, 2004 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01F23/266
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An improved system for generating a signal representative of the level of a material having a dielectric constant within a vessel is disclosed. The system features use of a first probe for generating a signal indicative of the dielectric constant of the material which is divided into a signal varying with the level of the material whereby a compensated level signal irrespective of the actual dielectric constant is measured. In a preferred embodiment, a single integrator is used to perform the division operation whereby inaccuracies due to component variation including long-term drift are eliminated. The instrument is disclosed as functioning in a two-wire instrument system having low power requirements, permitting use of conventional signal limits. Means for calibrating the instrument in a fail-safe manner such that the operator is assured of proper calibration are disclosed, as is means whereby bridge circuits used to measure in the capacitance measurements supplied to the division circuit are both supplied by a single oscillator means, again increasing reliability and accuracy of the system.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.