Level sensor apparatus and method
US4326851A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 24, 1980 |
| Grant date | Apr 27, 1982 |
| Priority date | — |
| Expiry date | Oct 24, 2000 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2035/1086
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A level sensor of a fluid transfer mechanism for determining when the bottom tip of a fluid aspirating probe touches or contacts the top surface of a sample fluid. The level sensor senses the contact capacitively by grounding one plate of a capacitor through the sample fluid and fluid aspirating probe. One capacitor plate is formed of an electrode biased against the bottom of a rotatable supply tray and positioned under a sample containing cavity in the tray. The other capacitor plate is formed by the bottom surface of the sample fluid in the supply cavity, and the dielectric of the capacitor is formed of the supply tray material. An AC signal is applied to the electrode and the probe is grounded. The change in voltage occurring in the AC signal at the electrode when the probe touches the top surface of the sample fluid it is sensed to provide the touch signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.