초록 ▼

A moisture sensor having an oscillator circuit with its output frequency directly proportional to moisture percentage present in the substance of interest. The oscillator circuit includes two spaced plates in the substance and functioning as a capacitor. The frequency of the oscillations changes as

A moisture sensor having an oscillator circuit with its output frequency directly proportional to moisture percentage present in the substance of interest. The oscillator circuit includes two spaced plates in the substance and functioning as a capacitor. The frequency of the oscillations changes as the capacitance between the plates changes due to the moisture present between the plates. The sensor is particularly adapted for use as a soil moisture detector and provides indications of wet or dry conditions.

대표청구항 ▼

A moisture sensor for detecting percentage moisture in a substance, said sensor being adapted to be coupled to indication means and comprising: a variable frequency oscillator having a pulsed output; plate capacitance means in said oscillator, the capacitance value thereof being responsive to the pe

A moisture sensor for detecting percentage moisture in a substance, said sensor being adapted to be coupled to indication means and comprising: a variable frequency oscillator having a pulsed output; plate capacitance means in said oscillator, the capacitance value thereof being responsive to the percentage of moisture between the plates of said capacitance means, the frequency of said oscillator being linearly related to the capacitance value of said capacitance means; timing means coupled to said oscillator output, said timing means having a set point, the output of said timing means depending on the value of said set point and being adapted to be coupled to the indication means, said timing means comprising: a first timing device having a predetermined first time-out period and comprising a retriggerable, monostable multivibrator, the output of which is constant when the period of the pulses from said oscillator is shorter than said first time-out period; and a second timing device having a predetermined second time-out period substantially longer than said first time-out period, said second timing device comprising a retriggerable, monostable multivibrator adapted to provide an enable signal to the indicating means when the period of the pulses from said oscillator is shorter than the time-out period of said first timing device; the output of said first timing device being pulsed when the period of the pulses from said oscillator is longer than said first time-out period, whereby said second timing device is adapted to provide a constant disable signal to the indication means; and means for varying the value of said set point, said set point varying means being connected to said first timing means so as to vary said first time-out period; said oscillator output being applied to said first timing device; said second timing device being coupled to the output of said first timing device and being adapted to be coupled to the indication means; whereby the moisture content at which said timing means is adapted to trigger the indication means is dependent on the value of said set point; whereby when the moisture percentage is above a value corresponding to the value of said set point, the output of said second timing device is adapted to trigger the indication means to indicate a high level of moisture in the substance; and when the moisture percentage is below a value corresponding to the value of said set point, the output of said second timing device is adapted to trigger the indication means to indicate a low level of moisture in the substance.