Moisture detection circuit
First Claim
1. A moisture detector comprising:
- an oscillator having an AC signal output;
a common electrode;
a detector electrode for placing in proximity to an object such that an impedance between the detector electrode and the common electrode is related to a moisture content of the object;
a first capacitor and a first resistor connected in series between the AC signal output of the oscillator and the detector electrode for driving the detector electrode with an AC signal which is affected by the impedance between the detector electrode and the common electrode such that a voltage level of the AC signal is thereby related to the moisture content of the object; and
a first diode connected between the detector electrode and a reference voltage node, whereby the voltage at the detector electrode is level shifted relative to a reference voltage at the reference voltage node.
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Accused Products
Abstract
A detector circuit in a moisture detector having an oscillator, a detector electrode and a common electrode for measuring the moisture content of wood and structural materials in buildings comprises a clamping diode network which couples an AC signal generated in the oscillator to a detector electrode. The clamping network clamps the AC signal to a reference voltage. The clamping network is balanced by a second clamping diode network which, together with a low pass filter, establishes the reference voltage. A low pass filter connected to the first clamping network produces an output voltage signal related to the impedance between the electrodes. To maintain the circuit'"'"'s stability, the diodes in the clamping networks are thermally coupled.
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Citations
29 Claims
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1. A moisture detector comprising:
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an oscillator having an AC signal output; a common electrode; a detector electrode for placing in proximity to an object such that an impedance between the detector electrode and the common electrode is related to a moisture content of the object; a first capacitor and a first resistor connected in series between the AC signal output of the oscillator and the detector electrode for driving the detector electrode with an AC signal which is affected by the impedance between the detector electrode and the common electrode such that a voltage level of the AC signal is thereby related to the moisture content of the object; and a first diode connected between the detector electrode and a reference voltage node, whereby the voltage at the detector electrode is level shifted relative to a reference voltage at the reference voltage node. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A detector circuit for a moisture detector comprising an oscillator, a detector electrode and a common electrode for placing in proximity to an object whereby an impedance between the electrodes is related to a moisture content of the object, the detector circuit comprising:
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a first capacitor having a first and a second terminal, the first terminal being connected to an AC signal output of the oscillator; a first resistor having a first terminal connected to the second terminal of the first capacitor and a second terminal connected to a first node, the first node being coupled to the detector electrode to drive the detector circuit with an AC signal having a voltage level affected by the impedance between the electrodes and thereby related to the moisture content of the object; and a first diode having a first terminal connected to the first node and a second terminal connected to a reference voltage node. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A moisture detector comprising:
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an oscillator for producing an AC signal at an output; a common electrode; a detector electrode for placing in proximity to an object whereby an impedance between the detector electrode and the common electrode is affected by a moisture content of the object; and a detector circuit for driving the detector electrode with the AC signal and applying a common voltage to the common electrode such that the AC signal is affected by the impedance between the detector electrode and the common electrode and thereby is related to the moisture content of the object, wherein the detector circuit comprises; a first capacitor having a first and a second terminal, the first terminal being connected to the oscillator output; a first resistor having a first terminal connected to the second terminal of the first capacitor and a second terminal connected to a first node, the first node being coupled to the detector electrode; and a first diode having a first terminal connected to the first node and a second terminal connected to a reference voltage node. - View Dependent Claims (24, 25, 26, 27, 28, 29)
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Specification