Detecting and identifying a change in a vibratory meter

1 . A meter electronics ( 20 ) for detecting and identifying a change in a vibratory meter ( 5 ), the meter electronics ( 20 ) comprising:

a processing system ( 202 ) including a storage system ( 204 ) configured to store a central tendency value of a meter verification parameter and dispersion value of the meter verification parameter, said processing system ( 202 ) being configured to:

obtain the central tendency value and the dispersion value from the storage system ( 204 ); and

determine a probability based on the central tendency value and the dispersion value to detect if the central tendency value is different than a baseline value, wherein the probability comprises a confidence interval of the central tendency value, wherein the confidence interval is compared to zero, and wherein:

if the confidence interval does not include zero, then detect that the central tendency value does not equal the baseline value; and

if the confidence interval includes zero, then detect that the central tendency value equals the baseline value;

determine a condition of the conduit ( 130 , 130 ′) based on a combination of:

a first detected stiffness change associated with a first location of a conduit ( 130 , 130 ′) of the vibratory meter ( 5 ); and

a second detected stiffness change associated with a second location of the conduit ( 130 , 130 ′) of the vibratory meter ( 5 ).

2 . The meter electronics ( 20 ) of claim 1 , wherein the processing system ( 202 ) being configured to determine a probability based on the central tendency value and the dispersion value comprises the processing system ( 202 ) being configured to calculate a t-value and calculate the probability using the t-value.

3 . The meter electronics ( 20 ) of claim 1 , wherein the processing system ( 202 ) being configured to determine the probability based on the central tendency value and the dispersion value comprises the processing system ( 202 ) being configured to calculate a degree-of-freedom based on the number of meter stiffness measurements comprising a meter stiffness.

4 . The meter electronics ( 20 ) of claim 3 , wherein the processing system ( 202 ) being configured to determine the probability based on the central tendency value and the dispersion value comprises the processing system ( 202 ) being configured to calculate a standard error based on a standard deviation and the degree-of-freedom.

5 . The meter electronics ( 20 ) of claim 4 , wherein the standard error is calculated using the following equation:

stderror

pooled

=

(

2

·

(

stddev

pooled

)

2

)

n

DOF

;

where:

stddev pooled is the meter stiffness standard deviation; and

n DOF is the degree-of-freedom.

6 . The meter electronics ( 20 ) of claim 1 , wherein the dispersion value is a pooled standard deviation comprising a standard deviation of meter stiffness measurements and baseline meter stiffness measurements.

7 . The meter electronics ( 20 ) of claim 1 wherein the central tendency value is a meter stiffness and the confidence interval of the meter stiffness is calculated using the following equation:

CI=Stiffness mean ±CI range ;

where:

CI is the confidence interval of the meter stiffness;

Stiffness mean is the meter stiffness obtained from the storage system ( 204 ); and

CI range is a confidence interval range calculated based on the meter stiffness standard deviation and a t-value.

8 . The meter electronics ( 20 ) of claim 7 , wherein the confidence interval range is calculated using the following equation:

CI range =stderror pooled ·t student,99,8 ;

where:

stderror pooled is the meter stiffness standard error; and

t student,99,8 is a t-value calculated based on a significance level and a degrees-of-freedom determined from a number of meter stiffness measurements comprising the meter stiffness.

9 . The meter electronics ( 20 ) of claim 1 , wherein the processing system ( 202 ) is further configured to set a bias dead band, wherein if the central tendency value is less than the bias dead band, then the meter stiffness is not detected as being different than the central tendency value.

10 . A method for detecting and identifying a change in a conduit of the vibratory meter, the method comprising:

obtaining a central tendency value of a meter verification parameter and a dispersion value of the meter verification parameter from a storage in a meter electronics of the vibratory meter; and

determining a probability based on the central tendency value and the dispersion value to determine if the central tendency value is different than a baseline value, wherein the probability comprises a confidence interval of the central tendency value, and wherein the confidence interval is compared to zero, wherein:

if the confidence interval does not include zero, then detect that the central tendency value does not equal the baseline value; and

if the confidence interval includes zero, then detect that the central tendency value equals the baseline value; and

determine a condition of the conduit ( 130 , 130 ′) based on a combination of:

a first detected stiffness change associated with a first location of a conduit ( 130 , 130 ′) of the vibratory meter ( 5 ); and

a second detected stiffness change associated with a second location of the conduit ( 130 , 130 ′) of the vibratory meter ( 5 ).

11 . The method of claim 10 , wherein determining the probability based on the central tendency value and the dispersion value comprises calculating a t-value and calculating the probability using the t-value.

12 . The method of claim 10 , wherein determining the probability based on the central tendency value and the dispersion value comprises calculating a degree-of-freedom based on a number of meter stiffness measurements comprising a meter stiffness.

13 . The method of claim 12 , wherein determining the probability based on the meter stiffness comprises calculating a standard error based on a standard deviation and the degrees-of-freedom.

14 . The method of claim 13 , wherein the standard error is calculated using the following equation:

stderror

pooled

=

(

2

·

(

stddev

pooled

)

2

)

n

DOF

;

where:

stddev pooled is the meter stiffness standard deviation; and

n DOF is the degrees-of-freedom.

15 . The method of claim 10 , wherein the dispersion value is a pooled standard deviation comprising a standard deviation of meter stiffness measurements and baseline meter stiffness measurements.

16 . The meter electronics ( 20 ) of claim 10 wherein the central tendency value is a meter stiffness and the confidence interval of the meter stiffness is calculated using the following equation:

CI=Stiffness mean ±CI range ;

where:

CI is the confidence interval of the meter stiffness;

Stiffness mean is the meter stiffness obtained from the storage system ( 204 ); and

CI range is a confidence interval range calculated based on a meter stiffness standard deviation and a t-value.

17 . The method of claim 16 , wherein the confidence interval range is calculated using the following equation:

CI range =stderror pooled −t student,99,8 ;

where:

stderror pooled is the meter stiffness standard error; and

t student, 99,8 is a t-value calculated based on a significance level and a degrees-of-freedom determined from a number of meter stiffness measurements comprising the meter stiffness.

18 . The method of claim 10 , further comprising setting a bias dead band, wherein if the central tendency value is less than the bias dead band, then the central tendency value is not detected as being different than the baseline value.