Apparatus for establishing and/or monitoring a predetermined filling level in a container through controlled transducer phase and impedance

US6138507A · kind A · utility

Assignee

• Endress+Hauser Inc. · DE

Inventors

• Igor Getman · Lörrach, DE
• Sergej Lopatin · Lörrach, DE
• Volker Dreyer · Lörrach, DE

Key dates

• Filing date: Apr 6, 1998
• Grant date: Oct 31, 2000
• Expiry date: Apr 6, 2018

Classification

• Technology area (CPC G): Physics
• CPC primary: G01F23/2967
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

An apparatus for establishing and/or monitoring a predetermined filling level in a container is described, in which a fixed phase difference (.DELTA..phi..sub.R), which is independent of the oscillation quality of the apparatus, exists between a transmission signal and a reception signal (E) at the resonant frequency (f.sub.r) of the mechanical oscillatory structure. This apparatus comprises a mechanical oscillatory structure (1), an electromechanical transducer (2) having at least one transmitter (23) and a receiver (24), an evaluation unit (9), which determines the frequency of the reception signal (E), compares it with a reference frequency (f.sub.R) and generates an output signal which indicates that the mechanical oscillatory structure (1) is covered by a charge material if the frequency has a value which is less than the reference frequency (f.sub.R) and a control loop, which regulates a phase difference existing between the electrical transmission signal and the electrical reception signal (E) to a specific, constant value at which the oscillatory structure (1) oscillates at a resonant frequency (f.sub.r). A reception signal line (6), which transmits the reception signal (E)…