Danfoss A/s

Frands W Voss

Henning M Hansen

James Digby Collier

Jens K Simonsen

Karsten Westermann

Niels H Gade

Richard-Jan E Jansen

Hans Jo Pedersen

Hans J&oslash;rgen Moos

Roger F Sewell

Niels Per Mondrup

In a circuit arrangement for deriving the measured variable from the signals (S to S ) of at least two sensors ( ) of a flow meter, which flow meter comprises one or several parallel fluid lines ( ) and means ( ) for exciting oscillations of a predetermined fundamental frequency (&ohgr;) in the fluid line(s), the sensors ( ) detect the oscillations and the sensor signals (S to S ) are supplied by way of a respective A-D converter ( ) to a digital processing unit (P) having a computation circuit ( ), in which their phase difference (&PHgr;) is determined as a measure of the flow. In order to be largely independent of unwanted changes in the fundamental frequency (&ohgr;) of the sensor signals (S , S ), and to measure the flow with little effort and with as few errors as possible, provision is made for the processing unit (P) between the A-D converter ( ) of each sensor signal (S , S ) and the computation circuit ( ) to comprise a digital multiplier circuit (M) and a digital filter arrangement (F) downstream thereof, for the digital sensor signals (S , S ) to be multiplied in the multiplier circuit (M) with respective digital signals (I, R) phase-displaced by 90&deg; with respect to one another that represent sinusoidal oscillations of identical maximum amplitude (x) and of a frequency (&ohgr;&plus;&Dgr;&ohgr;) that varies by a slight difference frequency (&Dgr;&ohgr;) from the fundamental frequency (&ohgr;), and for the pass band of the filter arrangement (F) to be matched to the difference frequency (&Dgr;&ohgr;).

Circuit arrangement for deriving the measured variable from the signals of sensors of a flow meter

Isolated liner for an electromagnetic flowmeter

The flow meter works on the Coriolis principle and has a measuring tube and at least two energy converters. At least one of the energy converters is an oscillation exciter for oscillating the tube to generate a wave traveling along the tube and an oscillation detector. An evaluating circuit uses the speed of travel of waves in the direction of flow of fluid through the tube and in the direction opposite the direction of flow to determine the mass flow of fluid through the tube.

Mass flow meter working on the coriolis principle

The invention relates to a magnetically inductive flow meter which generates a combined signal made up of a coil generated alternating voltage and an alternating simulated voltage. An evaluating circuit processes the combined signal to determine a flow rate output value in a manner which minimizes the temperature and time drift influences on the components of the flow meter.

Magnetic inductive flow meter

A mass flow meter based on the Coriolis principle. The meter has two rectilinear measuring tubes juxtaposed in parallel and mechanically connected at adjacent ends thereof. An oscillation generator is connected to the tubes between the ends thereof for driving the tubes in opposite directions. A sensor connected to the tubes on opposite sides of the oscillation generator sense and signal relative oscillations of the tubes which is indicative of the flow through the tubes. The measuring tubes have different bending strengths in two perpendicular axial planes thereof to reduce the amplitudes of vibration in the plane normal to the plane of interest. Individual masses applied to the measuring tubes cause the natural frequency of at least the first mechanical harmonic of the measuring tubes to differ from the natural frequency of the mechanical fundamental counter-oscillation by a factor x which differs from a whole number by at least 0.1.

Mass flow meter based on the coriolis principle

Growing community of inventors

Sonderborg, Denmark

Frands W Voss