US 5,555,190 A · Method and apparatus for adaptive line enhancement in Coriolis mass flow meter measurement

Abstract

An apparatus and method for determining frequency and phase relationships of vibrating flow tubes in a Coriolis mass flow meter. Adaptive line enhancement (ALE) techniques and apparatus are used in a digital signal processing (DSP) device to accurately determine frequency and phase relationships of the vibrating flow tube and to thereby more accurately determine mass flow rate of a material flowing through the mass flow meter. In a first embodiment, an adaptive notch filter is used to enhance the signal from each corresponding sensor signal on the vibrating flow tubes. In a second embodiment, a plurality of adaptive notch filters are cascaded to enhance the signal from each corresponding sensor signal. In both embodiments an anti-aliasing decimation filter associated with each sensor signal reduces the computational complexity by reducing the number of samples from a fixed frequency A/D sampling device associated with each sensor signal. Computational adjustments are performed to compensate for spectral leakage between the fixed sampling frequency and the variable fundamental frequency of the vibrating flow tubes. Despite this added computational complexity, the present invention is simpler than prior designs and provides better noise immunity due to the adaptive notch filtration. Heuristics are applied to the weight adaptation algorithms of the notch filters to improve convergence of the digital filters and to reduce the possibility of instability of the filters interfering with mass flow measurements.

Claims35

Dependent claims

An apparatus for measuring mass flow rate of a material in a Coriolis mass flow meter having a flow tube and having first and second sensors associated with said flow tube for generating output signals indicative of the oscillatory movement of said flow tube, said apparatus comprising:

analog to digital converter means for periodically sampling said sensor output signals and for converting sampled sensor output signals to digital form to generate a sequence of discrete sampled values representative of said output signals, including any undesirable components, of each of said first and second sensors;
digital notch filtration means, responsive to the generation of said sequence of discrete sampled values, for generating a sequence of discrete enhanced values, each discrete enhanced value corresponding to a sample of said sequence of discrete sampled values with said undesirable components removed;
phase value determination means, responsive to the generation of said sequence of discrete enhanced values, for generating the phase values of the oscillatory movement of said flow tube indicated by said sequence of discrete enhanced values;
phase difference means, responsive to the generation of said phase values, for determining a phase difference between the output signals of said first and second sensors;
and
mass flow measurement means, responsive to the determination of phase difference, for determining a mass flow rate value of the material flowing through the flow tube.

3 more elements

In a Coriolis mass flow meter having a flow tube and having first and second sensors associated with the flow tube for generating output signals indicative of the oscillatory movement of the flow tube, a method for measuring the mass flow rate of a material flowing through said flow tube of said flow meter comprising the steps of:

periodically converting analog output signals generated by the first and second sensors into digital form to generate a sequence of discrete sampled values representative of said output signals, including any undesirable components, of each of said first and second sensors;
applying said sequence of discrete sampled values to digital notch filtration means to generate a sequence of discrete enhanced values, each discrete enhanced value corresponding to a sample of said sequence of discrete sampled values with signals representative of noise removed;
applying said sequence of discrete enhanced values to phase value determination means to determine phase values of the oscillatory movement of the flow tube indicated by said sequence of said discrete enhanced values;
applying said phase values to phase difference computation means to determine a phase difference between the output signals of said first and second sensors;
and
determining the mass flow rate of the material flowing through said flow meter responsive to the determination of phase difference.

3 more elements

Dependencies are inferred from the claim text.

Method and apparatus for adaptive line enhancement in Coriolis mass flow meter measurement

Life of this patent

Method and apparatus for adaptive line enhancement in Coriolis mass flow meter measurement

Life of this patent

Abstract

Claims35