Radio Frequency State Variable Measurement System And Method

Abstract

A measurement system and method of conducting cavity resonance and waveguide measurements is disclosed. The cavity or waveguide may be used to monitor the amount, composition, or distribution of a material or sample contained in the cavity or waveguide or passing through the cavity or waveguide. Improved means for operating the measurement system to reduce measurement variability, improve measurement accuracy, and decrease measurement response times are described. The invention's broad applications range from measurements of filters, catalysts, pipe, and ducts where the material collected in or passing through the cavity or waveguide exhibits dielectric properties different from the material which it displaces.

What is claimed is: 
     
         1 . A radio frequency measurement system comprising:
 at least one radio frequency probe configured to transmit and receive radio frequency signals through a medium;   the medium containing a first material whose dielectric properties varies in a predetermined manner as a function of exposure to at least one second material to the medium; and   a control unit configured to determine accumulation of the second material on the medium, based on the received radio frequency signals.   
     
     
         2 . The radio frequency measurement system of  claim 1 , wherein properties of the first material are affected by the second material. 
     
     
         3 . The radio frequency measurement system of  claim 2 , wherein the first material interacts physically or chemically with the second material. 
     
     
         4 . The radio frequency measurement system of  claim 3 , wherein the first material stores the second material, thereby affecting a dielectric constant of the first material. 
     
     
         5 . The radio frequency measurement system of  claim 3 , where the first material causes oxidation of the second material. 
     
     
         6 . The radio frequency measurement system of  claim 3 , where the medium is a filter element, and the first material comprises a coating on the filter element. 
     
     
         7 . The radio frequency measurement system of  claim 3 , wherein the medium is a filter element, and the first material comprises particles embedded in the filter element. 
     
     
         8 . The radio frequency measurement system of  claim 1 , wherein the control unit determines accumulation based on a parameter computed from the received radio frequency signals, where the parameter is selected from the group consisting of absolute power attenuation, relative power attenuation, absolute phase shift and relative phase shift. 
     
     
         9 . The radio frequency measurement system of  claim 1 , wherein the medium is used for a first purpose, and the first material does not improve performance of the medium to perform the first purpose. 
     
     
         10 . A radio frequency measurement system, comprising:
 a sample conditioning system designed to control conditions of a sample;   a cavity in communication with the sample conditioning system;   at least one radio frequency probe configured to transmit and receive radio frequency signals through the cavity containing the sample; and   a control unit configured to determine at least one characteristic of the sample based on the received radio frequency signals under the controlled conditions.   
     
     
         11 . The radio frequency measurement system of  claim 10 , wherein the sample conditioning system adjusts a temperature of the sample. 
     
     
         12 . The radio frequency measurement system of  claim 10 , wherein the sample conditioning system adjusts an amount of moisture in the sample. 
     
     
         13 . The radio frequency measurement system of  claim 10 , further comprising a first sensor disposed in a conduit disposed upstream of the sample conditioning system and a second sensor disposed in a conduit disposed downstream of the sample conditioning system, wherein the control unit uses closed loop control to control the conditions of the sample. 
     
     
         14 . A radio frequency measurement system, comprising:
 a non-conductive conduit through which a sample is passed;   a conducting cavity positioned around at least a portion of the non-conductive conduit;   at least one radio frequency probe configured to transmit and receive radio frequency signals through the conducting cavity; and   a control unit configured to determine at least one characteristic of the sample based on the received radio frequency signals.   
     
     
         15 . The radio frequency measurement system of  claim 14 , where the non-conductive conduit and the conducting cavity have an annular configuration. 
     
     
         16 . The radio frequency measurement system of  claim 14 , where the non-conductive conduit directs the sample within a specific region of the conducting cavity. 
     
     
         17 . The radio frequency measurement system of  claim 16 , wherein the specific region is a region of low electric field. 
     
     
         18 . The radio frequency measurement system of  claim 16 , wherein the specific region is a region of high electric field. 
     
     
         19 . The radio frequency measurement system of  claim 14 , wherein the radio frequency probe is not exposed to the sample.