Mass flow meter with vibration sensor

US4488439A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Theodor Gast · Berlin, DE
• Kurt Binder · Stuttgart, DE
• Gunter Honig · Ditzingen, DE

Key dates

• Filing date: Aug 6, 1982
• Grant date: Dec 18, 1984
• Expiry date: Aug 6, 2002

Classification

• Technology area (CPC G): Physics
• CPC primary: G01F1/78
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

The mass flow rate of a fluid, for example a gas or air, for example passing through a duct or the like, is determined by placing a vibrating element in the path or stream of air flow, and measuring the damping thereof due to the air flow; the damping can easily be measured, in accordance with the invention, by connecting the vibrating element in a circuit having a servo system including a controlled variable amplifier and a comparator, such as a proportional-integral (PI) controller (14) comparing the signal on the vibrating element with a reference establishing a vibrating amplitude and, in turn, controlling the amplification of the variable amplification amplifier (8) to maintain a constant amplitude of vibration, the control signal controlling the variable amplification amplifier being a measure of the damping, and hence of mass flow rate. To eliminate damping due to extraneous conditions, such as clamping of the mechanical vibrating elements, connection of electrodes and the like, an alternating current (10a) can be fed to the vibrating element, the alternating current having a frequency which is high with respect to the vibration frequency, and then being filtered out by a ba…