Automated liquid level sensing system
US5627522A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 3, 1994 |
| Grant date | May 6, 1997 |
| Priority date | — |
| Expiry date | Jan 3, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2035/1086
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An automated liquid level sensing system for use in an automated, continuous, and random access analytical system is disclosed. A pipette probe is positioned above, and lowered into, a liquid sample container which contains the liquid to be detected. The probe is energized by a near radio-frequency (RF) signal source. A receiving antenna is positioned below the sample container, and is oriented so that very little signal is detected from the probe while the probe is in air. When the probe contacts liquid in the sample container, the electromagnetic field of the RF signal is increased and reoriented toward the receiving antenna. An autozero circuit maintains a near-zero output from the receiving antenna when slow changes in signal level occur due to changes in probe position or other environmental factors. The autozero circuit allows the sudden increase in signal amplitude, due to liquid contact, to pass to a receiver. A shield-driven triax cable connects the autozero circuit to the receiver, and significantly reduces the normal capacitance of the cable, enabling the signal change to be more easily detected.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.