Measuring apparatuses and methods of using them

Abstract

“A measuring instrument includes a transducer for measuring the depth of liquid and a transducer for measuring a physical parameter that causes interference error. A calibration polynomial is used to correct the output signal. The calibration polynomial includes the signal generated by the transducers as independent variables and the output signal as the dependent variable. The calibration polynomial is formed by a correction polynomial having at least one primary measurement signal and at least a first interference related signal as independent variables and a calibrated signal as a dependent variable. To form the calibration polynomial, a preliminary calibration polynomial including the primary independent variable and at least one interference related independent variable is developed. A plurality of data sets is generated from a test fixture. This data is used to eliminate the least significant terms of the preparatory calibration polynomial and to add the most significant cross terms”.

1 . A measuring instrument for measuring a value and providing a calibrated signal, comprising:
 at least one primary sensor for sensing the value wherein the at least one primary sensor generates a primary measurement signal;   at least one secondary sensor for generating at least one interference related signal for sensing at least one interference related value that reduces the precision of the primary measurement signal generated by the at least one primary sensor; and   a microcontroller containing a criteria optimized correction polynomial having the at least one primary measurement signal and said at least one interference related signal as independent variables and said calibrated signal as a dependent variable;   said microcontroller being connected to receive said at least one primary measurement signal and said at least one interference related signal, whereby said microcontroller corrects said at least one primary measurement signal for said at least one interference related signal to provide said calibrated signal.   
   
   
       2 . A measuring instrument in accordance with  claim 1  wherein the measuring instrument is an apparatus for determining a volumetric rate of flow of a liquid within a flow bed comprising:
 a measuring apparatus for measuring an average rate of flow of the liquid in the flow bed;   said at least one primary sensor being a pressure sensor, wherein the at least one primary sensor may be positioned at a bottom of a flow path for the liquid whereby the at least one primary measurement signal is related to the depth of the liquid;   said at least one secondary sensor being a temperature measuring sensor;   said criteria-optimized correction polynomial having depth and temperature as independent variables;   said microcontroller further including means for multiplying measured values by average velocity to provide a volumetric velocity.   
   
   
       3 . A measuring instrument in accordance with  claim 2  wherein the measuring apparatus comprises:
 means for transmitting an ultrasonic signal into the liquid in the flow bed;   means for receiving reflected ultrasonic signals; and   means for utilizing digital signals to calculate an approximate average velocity by performing a Fourier transform on the digital signals and averaging certain of the coefficients of the Fourier transform.   
   
   
       4 . A measuring instrument in accordance with  claim 2  wherein the measuring apparatus comprises:
 means for transmitting an ultrasonic signal into a fluid stream at an angle so that it traverses at least a representative portion of the cross sectional area of the fluid stream;   means for receiving reflected ultrasonic signals from said at least a representative portion of the cross sectional area of the fluid stream;   means for converting the received reflected ultrasonic signals to electrical signals representing reflection from said at least a representative portion of the cross sectional area of the fluid stream; and   means for utilizing substantially all of the electrical signals representing reflection from said at least a representative portion of the cross sectional area of the fluid stream to calculate an approximate average velocity of the fluid stream;   wherein said means for utilizing substantially all of the electrical signals representing reflection from at least a representative portion of the cross sectional area of the fluid stream to calculate an approximate average velocity of the fluid stream includes means for performing a Fourier transform on said electrical signals and averaging certain of the coefficients of the Fourier transform.   
   
   
       5 . A measuring instrument in accordance with  claim 1  wherein a primary value is temperature, the at least one primary sensor is an organic vapor chemical sensor and the at least one secondary sensor measures humidity. 
   
   
       6 . A method of making an instrument, comprising the steps of:
 selecting a design criteria;   preparing a criteria-optimized calibration curve;   selecting a primary transducer and at least one secondary transducer;   programming a microcontroller to correct a value measured by the primary transducer using the criteria-optimized calibration curve; and   using the corrected value.   
   
   
       7 . A method according to  claim 6  wherein the step of programming a microcontroller to correct the value measured by the primary transducer using the criteria-optimized calibration curve includes the steps of:
 forming a preparatory calibration polynomial that includes as terms a primary independent variable and at least one interference related independent variable;   obtaining a plurality of data sets of a dependent variable, the primary independent variable and the at least one interference related independent variable;   using the data sets to eliminate the least significant terms of the preparatory calibration polynomial; and   adding the most significant cross terms.