Capacitive type electromagnetic flowmeter

US4953408A · kind A · utility

Assignee

• Fischer & Porter GmbH · US

Inventors

• Eggert Appel · Dransfeld, DE
• Wilfried Kiene · Menden, DE
• Rudi Kuchemann · Hardegsen, DE
• Dieter Meier · Bad Nenndorf, DE
• Peter Neal Nissen · Frederikssund, DK

Key dates

• Filing date: Aug 30, 1989
• Grant date: Sep 4, 1990
• Expiry date: Aug 30, 2009

Classification

• Technology area (CPC G): Physics
• CPC primary: G01F1/60
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

An electromagnetic flowmeter in whose primary the fluid to be metered is conducted through a flow tube to intercept a composite magnetic field to induce therein a voltage which is picked up by capacitive metering electrodes. The composite field is formed by a low-frequency comparison field having a long period on which is superimposed a high-frequency switching field having a short period. The voltage from the capacitive electrodes is fed by way of a high pass filter to the input amplifier of a secondary whose amplified output is analyzed to provide separate components, one originating from the comparison field and the other from the switched field. An output signal is produced in accordance with the time phasing of these components, after compensating for the signal loss experienced in the filter by the comparison field component by means of a compensation voltage derived from the switched field component.