US 9,810,567 B2
Calibration-free continuous bin level sensor
Barry C. Mears, Auburn, IL (US)
Assigned to DICKEY-JOHN CORPORATION, St. Paul, MN (US)
Filed by DICKEY-john Corporation, Auburn, IL (US)
Filed on Apr. 30, 2014, as Appl. No. 14/265,957.
Claims priority of provisional application 61/819,373, filed on May 3, 2013.
Prior Publication US 2014/0326066 A1, Nov. 6, 2014
Int. Cl. G01F 23/26 (2006.01); G01F 23/00 (2006.01)
CPC G01F 23/266 (2013.01) [G01F 23/0069 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A sensor assembly for measuring the level of a material or fluid in a container or vessel comprising:
a sensing capacitive element configured from two parallel sensing electrodes positioned adjacent the container or vessel such that changes in a material level cause a proportionate change in a first capacitance of the sensing electrodes, the sensing capacitive element including a first ground electrode and a driven electrode coupled to a first oscillator, wherein said sensing first ground and driven electrodes have a length LL and a nominal capacitance per unit length C0;
a reference capacitive element configured from two parallel reference electrodes positioned adjacent to a bottom of the container or vessel, the reference capacitive element including a second ground electrode and a second driven electrode coupled to a second oscillator, said reference second ground and driven electrodes having a length LR and a capacitance per unit length C0, wherein said reference electrodes are in contact with the material or fluid within the container; and
an electronics module configured to measure a material or fluid level of the container, said electronics module having at least first and second oscillators, each of said oscillators coupled to a respective amplifier, said electronics module including a processor to process frequency signals received from each of the sensing and reference capacitive elements, each signal of which is a function of electrode capacitance, to be processed by said processor to determine a capacitance for each of said sensing and reference electrodes in each of an empty container and the container having the material or fluid therein, the processor multiplying a ratio of a sensing capacitance to a reference capacitance to a ratio of a length of the reference electrode to the sensing electrode to thereby calculate a level measurement of the material or fluid in the container.