Signal processing apparati and methods for attenuating shifts in zero intercept attributable to a changing boundary condition in a Coriolis mass flow meter

摘要

In the field of Coriolis mass flow meters, determination of the true zero of the meter has always been problematic due to zero drift effects with changing boundary conditions and fluid parameters. Disclosed are apparatus and methods for determining the true mass flow related component of the signal of the meter separately from errors caused by changing boundary conditions and fluid parameters. Accordingly, an apparatus for measuring a mass flow rate of a fluid flowing relative to a flow conduit includes: (1) a force driver for vibrating the flow conduit, (2) a sensor for measuring a resulting motion of the flow conduit and producing a sensed motion signal indicative thereof, the resulting motion containing a Coriolis mode component and a boundary condition mode component, (3) signal processing circuitry, coupled to the sensor to receive the sensed motion signal therefrom, for determining a magnitude of the Coriolis mode component of the resulting motion and (4) output circuitry for producing an output signal proportional to the mass flow rate, the output signal substantially free of influence from the boundary condition mode component of the sensed motion signal.