Technique for substantially eliminating temperature induced measurement errors from a coriolis meter
First Claim
1. Circuitry for measuring first and second input signals comprising:
- first, second and third input channels, having first, second and third channel inputs, for respectively producing first, second and third channel output signals in response to a predetermined characteristic of said first, second and third channel inputs;
measurement means comprising;
means, responsive to said first, second and third channel output signals for determining first and second internal offset values respectively associated with first and second pairs of said input channels and for respectively measuring first and second signal values through said first and second pairs so as to produce first and second measured signal values; and
means, responsive to said first and second measured signal values and said first and second internal offset values, for respectively compensating said first and second measured signal values by said first and second internal offset values to yield first and second compensated values, respectively, as measurements of said first and second input signals;
means for selectively routing said first or second input signals to corresponding inputs of said first, second and third input channels; and
control means, connected to said selectively routing means and to said measurement means, for specifying which one of said input signals is to be simultaneously applied as input to each one of the input channels and for operating said selectively routing means and said first and second pairs of the input channels in conjunction with said measurement means such that while the first pair is determining the first internal offset delay value the second pair is measuring the second signal value and for reversing operation of said channel pairs after a pre-defined interval of time has elapsed such that the first pair will measure the signal value while the second pair will determine the second internal offset delay value so as to continuously measure the first and second input signals and compensate measurements of the first and second input signals produced by each of the channel pairs by the value of the internal offset associated with that particular channel pair.
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Abstract
Apparatus and accompanying methods for inclusion in a Coriolis meter that substantially eliminate temperature induced measurement errors which might otherwise be produced by performance differences existing between the separate input channels contained in the meter. Specifically, two pairs of input channels are used in the meter. In operation, the meter repetitively measures the internal phase delay of each of these pairs and then subtracts the delay associated with each pair from actual flow based measurement data subsequently obtained therefrom. While one channel pair is measuring actual flow, the other channel pair is measuring its internal phase delay, with the channels being continuously cycled between these functions. Because both channel pairs are cycled at a sufficiently rapid rate, the current value of the internal phase delay for each of the pairs accurately reflects any temperature induced changes then occurring in the performance of that pair thereby eliminating substantially all temperature induced error components from the flow measurements subsequently obtained therefrom. In addition, the meter measures flow tube temperature in a manner that removes temperature induced errors therefrom.
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Citations
15 Claims
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1. Circuitry for measuring first and second input signals comprising:
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first, second and third input channels, having first, second and third channel inputs, for respectively producing first, second and third channel output signals in response to a predetermined characteristic of said first, second and third channel inputs; measurement means comprising; means, responsive to said first, second and third channel output signals for determining first and second internal offset values respectively associated with first and second pairs of said input channels and for respectively measuring first and second signal values through said first and second pairs so as to produce first and second measured signal values; and means, responsive to said first and second measured signal values and said first and second internal offset values, for respectively compensating said first and second measured signal values by said first and second internal offset values to yield first and second compensated values, respectively, as measurements of said first and second input signals; means for selectively routing said first or second input signals to corresponding inputs of said first, second and third input channels; and control means, connected to said selectively routing means and to said measurement means, for specifying which one of said input signals is to be simultaneously applied as input to each one of the input channels and for operating said selectively routing means and said first and second pairs of the input channels in conjunction with said measurement means such that while the first pair is determining the first internal offset delay value the second pair is measuring the second signal value and for reversing operation of said channel pairs after a pre-defined interval of time has elapsed such that the first pair will measure the signal value while the second pair will determine the second internal offset delay value so as to continuously measure the first and second input signals and compensate measurements of the first and second input signals produced by each of the channel pairs by the value of the internal offset associated with that particular channel pair. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. In circuitry for measuring first and second input signals, a method comprising the steps of:
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respectively producing through first, second and third input channels having first, second and third channel inputs first, second and third channel output signals in response to a predetermined characteristic of said first, second and third channel inputs; determining, in response to said first, second and third channel output signals, first and second internal offset values respectively associated with first and second pairs of said input channels and respectively measuring first and second signal values through said first and second pairs so as to produce first and second measured signal values; respectively compensating, in response to said first and second measured signal values and said first and second internal offset values, the first and second measured signal values by said first and second internal offset values to yield first and second compensated values, respectively, as measurements of said first and second input signals; selectively routing said first or second input signals to corresponding inputs of said first, second and third input channels; and specifying, to said selectively routing step, which one of said input signals is to be simultaneously applied as input to each one of the input channels, operating said selectively routing means and said first and second pairs of the input channels in conjunction with said measurement means such that while the first pair is determining the first internal offset delay value the second pair is measuring the second signal value and reversing operation of said channel pairs after a pre-defined interval of time has elapsed such that the first pair will measure the signal value while the second pair will determine the second internal offset delay value so as to continuously measure the first and second input signals and compensate measurements of the first and second input signals produced by each of the channel pairs by the value of the internal offset associated with that particular channel pair. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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Specification