JP2002357582A - Moisture detecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of a limit existing in measurement for needing a large dynamic range in a measuring range, the number of parts being numerous, experience needed for their adjustment and difficulty existing in performance holding. SOLUTION: A moisture sensor, whose electrostatic capacity changes is incorporated in an oscillation circuit system due to the difference of a dielectric constant of moisture, and change in the electrostatic capacity of the moisture sensor is converted into the change of a frequency with an oscillator. In this case, a capacitor is put between the moisture sensor and the oscillator. A CMOS timer is used in the oscillator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to water leakage, overflow, oil leakage,
The present invention relates to a moisture detecting device capable of detecting and determining the presence or absence of a liquid (moisture) such as rain and snow, the amount of the liquid, the type of the liquid, and the like.

[0002]

2. Description of the Related Art There are various types of moisture detecting devices for detecting liquids such as water and oil. The moisture detecting device is used for detecting water leakage around condominiums, detecting rain leakage from outside, detecting rainfall for controlling driving of a wiper of an automobile, and the like.

FIG. 4 shows a conventional moisture detector. In this method, a test signal from an oscillator is applied to a sensor unit, a change in voltage between the sensor units is measured by a voltmeter, and moisture is detected from the change.

[0004]

The moisture detecting device shown in FIG. 4 requires a large dynamic range in the measuring range depending on the sensor unit, so that the measurement is limited in some cases. In addition, the number of parts increases, and the adjustment of those components requires skill, and it is difficult to maintain the performance.

[0005]

As shown in FIG. 5 Means for Solving the Problems], when plate-like electrodes T ₁ of the area S, T ₂ is, which is two parallel spaced d, two electrode T _1, T ₂ When the battery E is connected to both electrodes, the positive and negative charges are equally distributed to both electrodes T ₁ and T ₂ . In this case, the capacitance (floating capacitance) C of the parallel electrodes T ₁ and T ₂ is expressed by the following equation (1). Therefore, the capacitance of the parallel electrodes T ₁ and T ₂ increases when the distance d is small and an electrode having a large area is formed. Further, it can be seen from the following equation (1) that the change is based on the difference in the relative dielectric constant (ε _r ) of the detection target. The present inventor has paid attention to the difference in the relative dielectric constant and the change in the capacitance C, and has earnestly studied the use of the difference for detecting a liquid, thereby completing the present invention. C = ε _r ε _O S / d (1) where d: interval between parallel plates S: area of parallel plates ε _r : relative permittivity of dielectric ε _O : permittivity of vacuum (natural constant)

In the moisture detecting device of the present invention, a moisture sensor whose capacitance changes due to a difference in the relative dielectric constant of water is incorporated in an oscillation circuit system, and a change in the capacitance of the moisture sensor is changed by an oscillator. Is converted to In this case, a capacitor is inserted between the moisture sensor and the oscillator.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a moisture detecting device according to the present invention will be described with reference to FIGS. The moisture detection device as in FIG. 1, the electrostatic capacitance by the difference in the dielectric constant of water is sensed moisture sensor 1 which changes (stray capacitance) C _x one end grounded and the other end of the oscillator 2 + Connected to the capacitor C ₁ connected to the pole, the change in the capacitance C _x of the moisture sensor 1 is sent to the oscillator 2, and a signal of a different frequency is output from the oscillator 2 in the oscillator 2 based on the capacitance C _x. It is oscillated and output from the output terminal of the oscillator 2.

The structure shown in FIG. 3 can be used as the moisture sensor 1 shown in FIG. In this method, two conductive detection lines 6 and 7 are provided in parallel on one side of an elongated insulating flexible substrate 5 at an interval, and both detection lines 6 and 7 are provided.
The detection projections 8 and 9 are alternately protruded from the inside to form a comb shape. When moisture comes in contact between the adjacent detection projections 8 and 9, the floating capacitance between the detection lines 6 and 7 changes. The detection lines 6 and 7 and the detection protrusions 8 and 9 are formed by printing a conductive paint on the flexible substrate 5 or coating a conductive material. A resin material is suitable for the flexible substrate 5, but the material, width, length, thickness and the like of the flexible substrate 5 can be arbitrarily selected according to the application. In addition, detection lines 6 and 7, detection protrusion 8,
Copper is suitable for the material of No. 9;
The interval between them, the interval between the detection protrusions 8 and 9, and the like can be arbitrarily selected according to the application.

The oscillator 2 has a CMOS (Complementar).
y Metal Oxide Semiconductor). Especially among CMOS, LMC555, TLC
555 etc. are suitable. The CMOS timer repeats charging and discharging, and in the cycle, the potential of the capacitor C is 1/3 Vdd
Until the charge reaches 2/3 Vdd. The CMOS timer has the following features. Low power consumption. Large noise margin and strong noise. Wide operating power supply voltage range. High input impedance and capacitive. High integration is possible. The present invention makes use of the high input impedance among these features. The oscillation frequency F of the oscillator 2 of FIG. 1 using a CMOS timer is determined by the following equation. F = (ln2) / R ₁ · C (2) where C = (C ₁ · C _x ) / (C ₁ + C _x ) R ₁ is the resistance in FIG.

The oscillator (CMOS) 2 has a DC power supply E
Is supplied with a DC voltage. DC power supply E is up to 15
About V is suitable. CMOS timer repeats charge and discharge
You. In the cycle, the potential of the capacitor C is 1/3 Vdd
Until discharge, and charge up to 2/3 Vdd. CMOS tie
The duty ratio of the output signal of the
₁= T_Two), The detection line of the moisture sensor 1
Prevents electrical contact due to electrolysis of 6, 7 and detection protrusions 8, 9
be able to.

A capacitor C1 is connected between the moisture sensor 1 and the oscillator 2. The capacitor C1 blocks a DC component and regulates the maximum applied voltage to the moisture sensor 1 (2/3 of the power supply voltage). If the capacitor C1 is not provided, the output becomes 0 V when the input terminal is short-circuited, and it becomes impossible to distinguish whether the power supply is cut off or the input terminal is short-circuited (signal system disconnection).
In the present invention the output signal of the prescribed even shorted input terminals because of the capacitor C ₁ is obtained. The capacitance of the capacitor C ₁ several 10 times to several 100 times the capacitance C _x of the moisture sensor 1 (C _1> C _x), for example, about 1000PF is suitable.

The electrodes of the moisture sensor 1 of FIG. 1 are normally in contact with air. When it rains or leaks,
The moisture contacts the electrode of the moisture sensor 1. In this case, the dielectric constant of water for different relative dielectric constant of air, the capacitance C _x of the moisture sensor is changed, the frequency oscillated from the oscillator 2 is also changed. The relationship between the frequency F _x (H _z ) at this time and the frequency F _air (H _z ) oscillated from the oscillator 2 when the electrode is in contact with _air is as follows. F _air >> F _x or F _air >> F _x Therefore, it is possible to easily detect moisture by comparing both frequencies.

The moisture sensor in the moisture detecting device of the present invention is usually arranged horizontally to detect moisture, but if it is arranged vertically, it can also detect the amount of moisture (moisture depth).

Table 1 shows an experimental example of moisture measurement by the moisture detector of the present invention.

[0015]

[Table 1]

[0016]

The moisture detecting device of the present invention has the following effects. 1. From the change in the oscillation frequency oscillated by the CMOS timer, the detection of moisture by the moisture sensor can be confirmed. 2. The conventional moisture detection device requires an oscillator system to be measured and a measurement (detection) system, but the moisture detection device of the present invention has a simple circuit configuration because the oscillator system also serves as the measurement system. Become. 3. Since the oscillation frequency from the CMOS timer has the following relationship, only grasping the frequency oscillated from the CMOS timer, the presence / absence of power supply, presence / absence of normal state, presence / absence of disconnection of the sensor system, presence of liquid Can be detected. F _open > F _set > F _leakage > F _short F _open : Frequency value of output signal when input terminal is open (H _z ) F _set : Output signal frequency when moisture sensor is set to input terminal (in air atmosphere) _3. Frequency value (H _z ) F _leakage : Frequency value of output signal when liquid contacts the moisture sensor (H _z ) F _short : Frequency value of output signal when input terminal is short-circuited (H _z ) The duty ratio of the output signal of the CMOS timer is 5
If it is 0%, it is possible to prevent the sensor from touching,
The deterioration of the moisture sensor with time is small, and high detection sensitivity can be maintained over a long period of time. 5. High detection accuracy because it is hardly affected by external environment such as temperature and humidity. 6. S of the formula (1) (the contact area of the moisture sensor), since the capacitance C _x of the moisture sensor by changing the d (gap between electrodes) is changed, it is possible to adjust the easy detection sensitivity. 7. Since the change in capacitance due to the difference in relative permittivity is used, even if the moisture sensor is coated with a resin film or resin to protect the moisture sensor, there is no effect on the detection sensitivity. Moisture can be detected with a sensitivity of.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an example of a moisture detecting device according to the present invention.

FIG. 2 is a schematic diagram of an example of a moisture detection device according to the present invention.

FIG. 3 is a plan view of an example of a moisture sensor in the moisture detection device of the present invention.

FIG. 4 is an explanatory diagram of a conventional moisture detection device.

FIG. 5 is an explanatory diagram of capacitance between parallel flat plates.

[Explanation of symbols]

1 Moisture sensor 2 Oscillator C ₁ Capacitor connected to oscillator C _x Capacitance of moisture sensor

Claims (2)

[Claims] 1. A moisture sensor comprising: a moisture sensor whose capacitance changes based on the relative permittivity of moisture detected; and an oscillator for converting a change in capacitance of the moisture sensor into a change in frequency. A moisture detecting device, wherein a capacitor is inserted between the moisture detecting device and the water detecting device. 2. The moisture detecting device according to claim 1, wherein the oscillator is a CMOS timer.