Method for the optical determining of a measured variable of a medium

US8625100B2 · kind B2 · utility

Assignee

• Endress+Hauser Conducta Gesellschaft fuer Mess- und Regeltechnik mbH + Co. KG · DE

Inventor

• Michael Hanko · Dresden, DE

Key dates

• Filing date: Jul 7, 2009
• Grant date: Jan 7, 2014
• Expiry date: Jun 7, 2030

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N2201/0691
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

In a method for determining a measured variable of a measured medium, wherein the measured medium is brought in contact with an indicator or an indicator mixture, whose absorption spectrum has a first, and a second, wavelength range, which essentially do not overlap, a first light source is activated for emitting a first light signal with a wavelength from the first wavelength range and a second light source is activated for emitting a second light signal with a wavelength from the second wavelength range. The intensity of the first light signal is modulated by a first and the intensity of the second light signal by a second, periodic signal, wherein at least a part of the first light signal and at least a part of the second light signal propagate as first and second measurement light signals along a measuring path and are transformed on the measuring path by optical interaction with the indicator or the indicator mixture to transformed measurement light signals, and wherein a total intensity of the transformed first and second measurement light signals is registered. The first periodic signal has a first phase difference relative to the second, periodic signal, and a second phase …