Excitation circuits for coriolis mass flowmeters

US6662120B2 · kind B2 · utility

Assignee

• Endress+Hauser Flowtec AG · CH

Inventors

• Wolfgang Drahm · Erding, DE
• Alfred Rieder · Landshut, DE
• Christian Matt · Lörrach, DE

Key dates

• Filing date: Jun 19, 2002
• Grant date: Dec 9, 2003
• Expiry date: Jun 25, 2022

Classification

• Technology area (CPC G): Physics
• CPC primary: G01F1/8477
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

Such an excitation circuit is intended for use in a Coriolis mass flowmeter which is connected to, is powered exclusively from, and outputs a measurement signal exclusively via, a two-wire process control loop. The Coriolis mass flowmeter has a vibrating flow tube and an excitation assembly for vibrating the flow tube at a frequency equal or adjacent to the instantaneous mechanical resonance frequency of the flow tube. It further comprises transducer assemblies which are positioned at a given distance from each other along the flow tube and provide respective transducer signals. The excitation circuit may comprise a peak detector to which one of the transducer signals is applied as an input signal, a comparsion stage which determines a deviation of the output signal of the peak detector from an adjustable reference signal that specifies an amplitude of the vibration of the flow tube, a multiplier for the input signal to the peak detector and the output signal from the comparsion stage, and an output stage having an input connected to an output of the multiplier and supplying the excitation assembly. Instead of the multiplier, a pulse duration modulator or a DC/DC converter and a co…