Liquid level and composition sensing systems and methods using emf wave propagation

Abstract

An automotive urea solution monitoring device is deployed in conjunction with the urea tank of a selective catalytic reduction vehicle. An RF signal of a constant frequency may be generated across a resonant circuit, which may be comprised of an inductor and a PCB trace capacitor, or the like. Electromagnetic radiation is propagated into the automotive urea solution in the urea tank. The conductivity and dielectric properties of the liquid change the impedance of the discrete/trace capacitor and or the discrete/trace inductor. These changes are proportional to ammonia content, temperature, and/or level of the automotive urea solution in the urea tank and are preferably detected by a microcontroller, or the like, and then transmitted to a selective catalytic reduction vehicle engine management system, or the like.

1 - 35 . (canceled) 
     
     
         36 . A monitoring device comprising:
 an antenna driver having output terminals, and input terminals, coupled to an RF generator;   a resonant circuit coupled to the antenna driver and having an inductor positioned proximate a liquid in a container or tank; and   a controller, the controller including the RF generator, the controller controlling an operating frequency of the RF generator to be proximate to a resonant frequency of the resonant circuit and measuring a change in an electrical parameter associated with the resonant circuit caused by changes in said liquid in said tank.   
     
     
         37 . The device of  claim 36 , wherein said liquid is an automotive urea solution. 
     
     
         38 . The device of  claim 37  wherein said changes in said liquid comprises a change in level of said urea in said tank. 
     
     
         39 . The device of  claim 37  wherein said changes in said liquid comprises a change in concentration of said urea. 
     
     
         40 . The device of  claim 37  wherein said changes in said liquid comprises a change in ammonia concentration of said urea. 
     
     
         41 . The device of  claim 36 , wherein the controller, antenna driver, and resonant circuit are mounted on a printed circuit board. 
     
     
         42 . The device of  claim 36 , wherein the sensor is installed external to the container or tank. 
     
     
         43 . The device of  claim 36 , wherein the resonant circuit includes a capacitor. 
     
     
         44 . The device of  claim 43 , wherein said capacitor is a printed circuit board trace capacitor. 
     
     
         45 . The device of  claim 41 , wherein said printed circuit board is a flexible printed circuit board. 
     
     
         46 . A system comprising:
 an RF generator functional to generate an RF signal at an operating frequency;   an antenna circuit electrically coupled to the RF generator, the antenna circuit comprising a resonant circuit and a radiating component mounted proximate to a urea tank, the resonant circuit having a resonant frequency; and   a controller operatively connected to the RF generator and to the antenna circuit, the controller being functional to sweep between a range of a frequencies, from a first frequency to a second frequency, to identify a signal at said resonant frequency within said range and measuring a change in an electrical parameter of said signal associated with the resonant circuit caused by changes in a concentration of ammonia in urea in said tank.   
     
     
         47 . The system of  claim 46  wherein the controller is further functional to transmit the measured change in the electrical parameter. 
     
     
         48 . The system of  claim 46  wherein the controller is further functional to convert the measured change in the electrical parameter to an ammonia concentration signal and to transmit the ammonia concentration signal to an engine management system of a selective catalytic reduction vehicle. 
     
     
         49 . The system of  claim 46 , wherein the resonant circuit is a series resonant circuit, and the controller further comprises a calibration module operative to sweep between a range of a frequencies, from a first frequency to a second frequency, to identify a signal at said resonant frequency within said range and measuring a change in an electrical parameter of said signal associated with the resonant circuit caused by changes in concentration of ammonia said urea in said tank. 
     
     
         50 . The system of  claim 46 , wherein the controller further comprises a compensation module functional to adjust the ammonia concentration signal for changes in ambient temperature. 
     
     
         51 . The system of  claim 46 , wherein the controller further comprises a compensation module functional to adjust the ammonia concentration signal for changes in temperature of the liquid in the tank.