Measuring and testing – Liquid level or depth gauge – Hydrostatic pressure type
Patent
1999-05-28
2000-03-07
Williams, Hezron
Measuring and testing
Liquid level or depth gauge
Hydrostatic pressure type
73756, G01F 2300
Patent
active
060325291
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.
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patent: 5005408 (1991-04-01), Glassey
patent: 5599105 (1997-02-01), Ridley et al.
patent: 5636547 (1997-06-01), Raj et al.
patent: 5661228 (1997-08-01), Young
patent: 5802910 (1998-09-01), Krahn et al.
Fujimoto Hisashi
Saito Kyoko
Sato Nobuyoshi
Seto Hideaki
Yamamoto Haruhiko
LSI Logic Corporation
Tran Thuy Vinh
Williams Hezron
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