Capacitive fill level sensor

US9658095B2 · kind B2 · utility

Assignee

• BALLUFF GMBH · DE

Inventors

• Frank Winkens · Ludwigshafen, DE
• Juergen Glock · Hirschberg, DE

Key dates

• Filing date: Apr 8, 2014
• Grant date: May 23, 2017
• Expiry date: May 12, 2034

Classification

• Technology area (CPC G): Physics
• CPC primary: G01F23/268
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A capacitive fill level sensor for measuring the fill level of a medium in a container has an electrode unit, which contains a strip-shaped measurement electrode, a strip-shaped counter electrode and a strip-shaped shielding electrode, the shielding electrode at least partially surrounding the measurement electrode. A first AC voltage source having a predefined frequency and amplitude is provided, to which the shielding electrode is connected such that a shielding capacitor formed between the shielding electrode and the measurement electrode has a shielding capacitance that is proportional to the length of the shielding electrode. A second AC voltage source of equal frequency and a predefined second amplitude is provided, the second amplitude being in phase opposition to the first amplitude, to which AC voltage source the counter electrode is connected, such that a measurement capacitor formed between the counter electrode and the measurement electrode has a measurement capacitance that is proportional to the fill level. The measurement electrode voltage present at the measurement electrode is used to determine the fill level.