Capacitive fluid level sensor
US5042299A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 23, 1990 |
| Grant date | Aug 27, 1991 |
| Priority date | — |
| Expiry date | Jul 23, 2010 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01F23/266
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A linear compensated capacitive fluid-level sensing device includes three capacitors. A measurement capacitor is positionable during use to receive a fluid. A compensation capacitor is submerged in the fluid so that the fluid fills the space between the electrodes. An offset capacitor has a capacitance equivalent to the capacitance of the measurement capacitor when only air exists between the measurement electrodes. Charge applied to each of the three capacitors is discharged to an associated differential amplifier through a respective switch when the capacitors are disconnected from a charging voltage supply. The offset amplifier generates an inverted output current that is applied to the discharge currents of the measurement and compensation amplifiers. The compensation amplifier output gates a frequency-controlled oscillator that in turn controls the switches.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.