Fluid condition monitoring using broad spectrum impedance spectroscopy

Abstract

Impedance spectroscopy is used to determine values associated with properties of a substance such as a fluid. In some embodiments, the present invention is applied to engine lubricants. A spectral matrix is constructed that comprises data taken from spectral plots. Also constructed is a result matrix comprising known quantities of a plurality of fluid constituents. A known analytic technique is performed on the spectral matrix to identify at least one principal component having significant influence on the spectral matrix. A reduced spectral matrix, wherein each column in the reduced spectral matrix is associated with a principal component having significant influence on the spectral matrix, is next created. A statistical technique uses the reduced spectral matrix and the result matrix to create at least one prediction equation. The prediction equation is used to predict at least one property in a second substance in situ.

1 - 63 . (canceled)  
   
   
       64 . A method of creating an information library comprising information about a substance, comprising the steps of: 
 (1) generating a plurality of first plots of spectra over a range of frequencies; and    (2) creating a second plot that comprises the plurality of first plots by sequentially assigning x-values to selected frequencies in the plurality of first plots.    
   
   
       65 . The method of  claim 64 , further comprising: 
 (3) repeating steps (1)-(2) at least once to generate a plurality of second plots.    
   
   
       66 . The method of  claim 65 , further comprising building a spectral matrix that comprises data taken from the plurality of second plots.  
   
   
       67 . The method of  claim 65 , wherein the plurality of first plots comprises at least one Bode plot.  
   
   
       68 . The method of  claim 65 , wherein at least one of the plurality of first plots comprises at least one datum derived from a Nyquist plot.  
   
   
       69 . The method of  claim 68 , wherein the at least one datum derived from a Nyquist plot includes at least one datum from the bulk region of the Nyquist plot and at least one datum from the interfacial region of the Nyquist plot.  
   
   
       70 . The method of  claim 66 , wherein at least one of the plurality of first plots is a plot of resistive impedance spectra.  
   
   
       71 . The method of  claim 70 , wherein at least one of the plurality of first plots is a plot of reactive impedance spectra.  
   
   
       72 . The method of  claim 64 , wherein the range of frequencies is between approximately 75 kilohertz and 0.0075 hertz.  
   
   
       73 . The method of  claim 66 , further comprising performing a Principal Component Analysis on the spectral matrix.  
   
   
       74 . The method of  claim 73 , further comprising using the results of the Principal Component Analysis to create a reduced spectral matrix having at least one column.  
   
   
       75 . The method of  claim 74 , further comprising using a regression plot to analyze the results of the Principal Component Analysis.  
   
   
       76 . The method of  claim 74 , further comprising applying a pre-processing function to the spectral matrix before performing a Principle Component Analysis on the spectral matrix.  
   
   
       77 . The method of  claim 74 , further comprising building a result matrix comprising known quantities of a plurality of components in the substance.  
   
   
       78 . The method of  claim 77 , further comprising performing a statistical technique that uses the reduced spectral matrix together with the result matrix to create at least one prediction equation.  
   
   
       79 . The method of  claim 78 , further comprising using the at least one prediction equation to predict at least one property in a second substance.  
   
   
       80 . The method of  claim 79 , further comprising predicting the at least one property in the second substance in situ.  
   
   
       81 . The method of  claim 79 , further comprising providing an end of life (EOL) indication for the second substance when the amount of at least one of the at least one properties in the second substance has reached a predetermined value.  
   
   
       82 . The method of  claim 79 , further comprising providing a remaining useful life (RUL) indication for the second substance by comparing at least one of the at least one properties in the second substance to at least one baseline value for the substance.  
   
   
       83 . The method of  claim 78 , wherein the statistical technique is selected from the group consisting of Multivariate Least Squares Regression, Principle Component Regression, and Group Methods of Data Handling.  
   
   
       84 - 120 . (canceled)  
   
   
       121 . A method of creating an information library comprising information about a substance, comprising the steps of: 
 (1) generating a plurality of first plots of spectra over a range of frequencies, wherein at least one of the plurality of first plots comprises at least one Bode plot, and wherein at least one of the plurality of first plots comprises at least one datum derived from a Nyquist plot; and    (2) creating a second plot that comprises the plurality of first plots by sequentially assigning x-values to selected frequencies in the plurality of first plots.