Patent ID: 6420882
Filing Date: 2002-07-16
Classification: G01F,G01N

Abstract:
An apparatus for detection or measurement of a medium using electrical capacitance, comprising:at least one electrode, wherein a capacitance to be measured is between said at least one electrode and a counter-electrode and said capacitance is of a medium being measured or detected; a lead conductor for connecting the at least one electrode to an associated LC-oscillator circuit, said conductor having a substantially smaller capacitance than a capacitance of the at least one electrode; the associated LC-oscillator circuit being comprised of an air coil and being operative for generating an output frequency which is a function of the capacitance associated with the at least one electrode and a dielectric constant of the medium, said output frequency being taken as a basis for the detection or measurement; a temperature sensing element for generating a temperature measuring signal to provide for temperature compensation; an analog-digital converter for receiving the temperature measuring signal and for outputting a corresponding digital temperature signal; a frequency counter for receiving the output frequency and for outputting a corresponding digital frequency signal to a microprocessor; and a microprocessor for receiving the digital temperature signal and the digital frequency signal and for computing a detection or measurement signal using the digital frequency signal and the digital temperature signal.