초록 ▼

A sensing device includes a pair of sensing electrodes disposed within a medium and a circuit connected to the sensing electrodes via impedance matching networks for producing an output signal which varies in response to a capacitive change in the medium. The circuit includes a first circuit portion

A sensing device includes a pair of sensing electrodes disposed within a medium and a circuit connected to the sensing electrodes via impedance matching networks for producing an output signal which varies in response to a capacitive change in the medium. The circuit includes a first circuit portion including the sensing electrodes and a second circuit portion including the oscillator. The first and second circuit portions are tuned to match their impedance for more accurately measuring the capacitive changes.

대표청구항 ▼

[ What is claimed is:] [1.] A moisture sensing device for measuring the moisture content of a medium, comprising:a pair of sensing electrodes disposed within said medium;a circuit connected to said pair of sensing electrodes for producing an output signal which varies in response to a change in the

[ What is claimed is:] [1.] A moisture sensing device for measuring the moisture content of a medium, comprising:a pair of sensing electrodes disposed within said medium;a circuit connected to said pair of sensing electrodes for producing an output signal which varies in response to a change in the dielectric constant of said medium, said circuit comprisingan oscillator providing a signal having a constant frequency;an electrode circuit portion including said sensing electrodes and said medium, said electrode circuit portion having an output resistance sufficiently low to be insensitive to a chance in conductance of the medium, and an output reactance which varies substantially in response to the change in the dielectric constant of said medium, said electrode circuit portion providing the output signal; anda matching circuit portion, coupled between the oscillator and the electrode circuit portion, the impedance of the matching circuit portion approximately matching the impedance of the electrode circuit portion at the constant frequency, if the medium has a predetermined condition, wherein a measurable mismatch occurs when the dielectric constant of said medium varies from the dielectric constant at the predetermined condition, indicating a change in moisture content of said medium.