Liquid level sensor for buffered hydrofluoric acid
US6032529A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 28, 1999 |
| Grant date | Mar 7, 2000 |
| Priority date | — |
| Expiry date | May 28, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01F23/165
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An object of the present invention is to prevent erroneous operation of a liquid level sensor due to deposition of ammonium fluoride dissolved in buffered hydrofluoric acid used as a process solution. The present invention provides a liquid level sensor comprising a chemical solution bath for receiving a chemical solution including buffered hydrofluoric acid, a gas feed tube for introducing a gas for detecting the variation in the liquid level of said chemical solution into said chemical solution, and a gas pressure detector for detecting a change in the pressure of said gas and converting it into an electric signal to indicate a change in liquid level, characterized in that the diameter of a gas outlet provided at an end of said gas feed tube is smaller than the inner diameter of said gas feed tube.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.