The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 06, 2004
Filed:
Apr. 27, 2001
Shori Mokuo, Tosu, JP;
Tokyo Electron Limited, Tokyo, JP;
Abstract
Apparatus and method for correctly detecting the level of a processing liquid such as HPM in a processing tank in the event that any drift occurs in a detector is disclosed. A liquid level detecting apparatus ( ) comprises a pressure sensor ( ) operable to generate an output signal S which is maintained at a constant signal level until the level of HPM reaches a predetermined position M in the tank and rises in the signal level as the liquid level rises in the tank after reaching the predetermined position M, a determination circuit ( ) for determining whether the liquid level reaches the predetermined position M and a liquid level detecting circuit ( ) for detecting the liquid level. The output signal S from the pressure sensor is input to an amplifier ( ). The liquid level detecting circuit ( ) comprises a low-pass filter ( ) which receives the amplified signal and generates an output pressure signal S The liquid level detecting circuit ( ) is operable to calculate any difference between the output signal S from the low-pass filter and a correction signal &Dgr;S generated by a signal holding circuit ( ).