JP2003202312A - Moisture content sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a moisture content sensor that can obtain stable sensor output without any variation in detection characteristics. <P>SOLUTION: The capacitive connection between an outer-periphery electrode 42 and a guard electrode 43 is secured by an object to be detected, the outer- periphery and guard electrodes 42 and 43 are driven in-phase, thus preventing an electric field from being formed between the outer-periphery and guard electrodes 42 and 43 that are driven in-phase, and separating an electric field region formed by a center electrode 41 and the outer-periphery electrode 42 from that formed by the guard electrode 43 and a peripheral metal container 2. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water content sensor for detecting the amount of water contained in an object to be detected by capacitance or impedance.

[0002]

2. Description of the Related Art FIG. 29 shows the structure of a conventional water content sensor used in a food waste processing machine. The water content sensor shown in the drawing is a metal as a waste processing tank in which the food waste 1 to be detected is stored. A detection electrode portion formed of a pair of parallel detection electrodes 4 and 4 attached to the inner bottom portion of an electrode case 3 made of an insulating material fitted into the peripheral wall of the container 2, and the detection electrodes 4 and 4 at the electrode connection ends of the pair. The capacitance C between the detection electrodes 4 and 4 is connected.
Oscillation circuit 5 that uses 0 as a capacitor to determine the oscillation frequency, outputs the capacitance that changes according to the amount of water (water content) contained in raw garbage 1 after converting the output frequency, and the output of this oscillation circuit 5. A phase comparator 6 for inputting a frequency, a low-pass filter 7 ,. It is composed of a PLL circuit composed of a voltage controlled oscillator (VCO) 8 and converts the DC voltage corresponding to the input frequency output from the low-pass filter 7, that is, the electrostatic capacity corresponding to the water content of the garbage 1 into a DC voltage. It is composed of a capacitance detection circuit 9 that outputs as a sensor output, and an output circuit 10 that converts the output voltage of the capacitance detection circuit 9 into a desired voltage corresponding to the moisture content and outputs the sensor output.

In the water content sensor having such a configuration, capacitive coupling (sensing electrode) is provided between each sensing electrode 4 and the peripheral wall of the surrounding metal container 2 due to the object to be sensed (raw dust 1 in the illustrated example). 4 and the capacitance C) between the circuit ground and the circuit ground are generated respectively.

Therefore, as shown in FIG. 30, a capacitance C is provided between the electrode connection end connecting the electrostatic capacitance C0 that determines the oscillation frequency of the oscillation circuit 5 and the circuit ground.

As a result, although the degree of influence varies depending on the configuration of the oscillation circuit 5, the relationship between the oscillation frequency (MHz) and the water content (%) of the oscillation circuit 5 depends on the size of the capacitance C between the detection electrode 4 and the circuit ground. The characteristics are as shown in FIG. In FIG. 31, the vertical axis represents the oscillation frequency (MHz), and the horizontal axis represents the water content (%). In the graph (a), when the capacitance C is not present, in the graph (b), the capacitance C is 2 pF. In this case, the graph (c) shows the case where the capacitance C is 7 pF, and the graph (d) shows the case where the capacitance C is 10 pF.

Further, since the capacitance value between the detection electrode 4 and the circuit ground also changes depending on the composition of the object to be detected and the amount of water, the change in the oscillation frequency of the oscillation circuit 5 with respect to the change in the amount of water is not constant, and the water amount sensor There was a problem in that the detection characteristics of were different.

Further, as shown in FIG. 32, the arrangement of the detection electrodes 4 and 4 is the same as that of the conventional example shown in FIG. 29. The oscillation circuit 5 oscillates at a constant frequency, and the oscillation output of the oscillation circuit 5 is composed of resistors. An operational amplifier 11 for inputting and amplifying via an impedance element Z ₀ and a detection circuit 1 for detecting an amplified output.
2, the impedance value Zd consisting of the electrostatic capacitance between the detection electrodes 4 and 4 is used as a factor for determining the amplification factor of the operational amplifier 11, and the impedance value Zd depending on the water content of the garbage 1 as the detection object is Change the operational amplifier 11
Of the impedance detection circuit 13 that outputs a DC voltage corresponding to the amplification rate from the detection circuit 12, and the output voltage of the impedance detection circuit 13 is converted into a desired voltage corresponding to the amount of water to obtain a sensor output. A moisture sensor including an output circuit 10 for outputting is also conventionally provided.

In this conventional example, the capacitance C between the detection electrode 4 and the circuit ground becomes the load capacitance of the oscillation circuit 5 and the input capacitance and load capacitance of the operational amplifier 11, so that the output of the oscillation circuit 5 decreases and the calculation is performed. This leads to an oscillation phenomenon of the amplifier 11, resulting in variations in the detection characteristics of the water content sensor and malfunctions.

As another conventional example, as shown in FIG. 33 (a), a circular center electrode 41 and an annular outer peripheral electrode 42 arranged concentrically around the center electrode 41 as a center. There is also a configuration in which the detection electrode section is configured by the above, and the impedance value Zd between the electrodes 41 and 42 is converted into the amplification factor of the operational amplifier 11 of the impedance detection circuit 13 as in the conventional example of FIG. As in the conventional example of FIG. 32, however, there is a problem that the capacitance C between the outer peripheral electrode 42 and the ground (X) of the metal container 2 becomes a load capacitance and the operation of the operational amplifier 11 becomes unstable (oscillation, etc.). It was Note that FIG.
(B) is an equivalent circuit of FIG.

The capacitance C between the metal container 2 and the ground (X)
As shown in FIGS. 34 (a) and 34 (b), there is a conventional example in which the impedance detection circuit 13 is connected to the input terminal of the operational amplifier 11, but in this conventional example, the capacitance C is the input capacitance of the operational amplifier 11. Therefore, the operation of the operational amplifier 11 becomes unstable (oscillation, etc.).

Further, as shown in FIG. 35 (a), the oscillation circuit 5
Oscillation output and the input terminal (inverting input terminal) of the operational amplifier 11
There is also a conventional example in which an impedance Zd, which is a capacitance between the center electrode 41 and the outer peripheral electrode 42, is inserted between and. In this conventional example, the impedance Zd and the capacitance C between the outer peripheral electrode 42 and the ground (X) become the load capacitance of the oscillation circuit 5,
Since the oscillation output fluctuates, there is a problem that an output error of the water content sensor occurs. For example, when the water content of the object to be detected is high, the capacitance C between the outer peripheral electrode 42 and the ground (X) becomes large, and the load of the oscillation circuit 5 becomes a low impedance load. There was a problem that the output could not be maintained. Note that FIG. 35 (b) is an equivalent circuit of FIG. 35 (a).

The capacitance C between the metal container 2 and the ground (X)
As shown in FIGS. 36 (a) and 36 (b), there is a conventional example in which the capacitance C is connected to the input of the operational amplifier 11 of the impedance detection circuit 13, but in this conventional example, the capacitance C is the operational amplifier 1.
However, there is a problem in that the operation capacity of the operational amplifier 11 becomes unstable (oscillation, etc.) due to the input capacitance of 1.

Further, as shown in FIG. 37, the center electrode 41 and the outer peripheral electrode 42 constitute a detection electrode portion, and the oscillation frequency of the oscillation circuit 5 is changed by the capacitance Cd due to the object to be detected between the electrodes 41 and 42. There is also a water content sensor in the past, but in this conventional example, it is difficult to obtain stable operation due to various grounding conditions, and when used in a garbage processing machine, the size of the processing tank and the amount of garbage etc. There was a problem that its stability changed.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a moisture sensor capable of obtaining a stable sensor output without variations in detection characteristics. To provide.

[0015]

In order to achieve the above object, in the invention of claim 1, the object to be detected in the metal container is surrounded by the peripheral wall of the metal container for housing the object to be detected. The oscillation frequency is determined by the capacitance between the first electrode and the second electrode formed so as to surround the first electrode and the first electrode opposite to the first electrode, and the capacitance between the first and second electrodes. An oscillation circuit that changes, a capacitance detection circuit that converts the oscillation frequency of the oscillation circuit into a voltage that corresponds to the moisture content of the object to be detected, and outputs the output voltage of the capacitance detection circuit to a desired voltage that depends on the moisture content. A water content sensor configured by an output circuit for converting and outputting, includes a third electrode arranged so as to surround the detection electrode portion, and the third electrode and the second electrode are provided in the same manner. It is characterized by driving in phase.

According to a second aspect of the invention, in the first aspect of the invention, the driving of the third electrode and the second electrode in the same phase is performed by capacitive coupling by the detection object. .

According to a third aspect of the invention, in the first aspect of the invention, the driving of the third electrode and the second electrode in the same phase is performed, and the oscillation output end of the oscillation circuit is connected to the third electrode. It is characterized by performing by doing.

According to a fourth aspect of the invention, in the first aspect of the invention, the driving of the third electrode and the second electrode in the same phase is performed between the output end of the oscillation circuit and the third electrode. It is characterized by performing the connection through an impedance element having a constant impedance value.

According to a fifth aspect of the present invention, in the first aspect of the invention, the third electrode and the second electrode are driven in phase, and the electrode connection end of the oscillation circuit that connects the second electrode is connected. And the third electrode are connected via an impedance element having a constant impedance value.

According to a sixth aspect of the invention, in the first aspect of the invention, the electrode connection end of the oscillation circuit is connected to drive the third electrode and the second electrode in phase with each other. And the third electrode are connected via a buffer circuit.

According to a seventh aspect of the invention, in the first aspect of the invention, the electrode connection end of the oscillation circuit is connected to the second electrode for driving the third electrode and the second electrode in the same phase. And the third electrode are connected via an inverter circuit.

According to an eighth aspect of the invention, in the first aspect of the invention, the driving of the third electrode and the second electrode in the same phase is performed by the oscillation output end of the oscillation circuit and the third electrode. It is characterized in that it is performed by connecting the two via a buffer circuit.

According to a ninth aspect of the present invention, in the first aspect of the invention, the driving of the third electrode and the second electrode in the same phase is performed by the oscillation output end of the oscillation circuit and the third electrode. It is characterized by performing the connection between the two via an inverter circuit.

According to a tenth aspect of the present invention, the first electrode and the first electrode that are opposed to the object to be detected in the metal container are surrounded by the peripheral wall of the metal container that houses the object to be detected. Between the first and second electrodes, a sensing electrode portion formed of a second electrode formed so as to surround the oscillation electrode, an oscillation circuit connecting an oscillation output of a constant frequency between the second electrode and ground. Impedance conversion circuit that outputs the voltage corresponding to the moisture content of the object to be detected and the output voltage of the impedance detection circuit is converted to a desired voltage corresponding to the moisture content and output. A water content sensor including an output circuit, comprising a third electrode arranged so as to surround the detection electrode portion, and driving the third electrode and the second electrode in the same phase. Is characterized by.

According to an eleventh aspect of the invention, in the tenth aspect of the invention, the oscillation output end of the oscillation circuit is connected to the first electrode.

The invention of claim 12 is characterized in that, in the invention of claim 10, the oscillation output end of the oscillation circuit is connected to the second electrode through a known impedance element.

According to a thirteenth aspect of the invention, in the tenth aspect of the invention, the oscillation output end of the oscillation circuit is connected to the first electrode through a known impedance element.

According to the invention of claim 14, claims 11 to 1
In the invention of any one of 3), the oscillation output end of the oscillation circuit is connected to the third electrode via a buffer circuit or an inverter circuit.

In the invention of claim 15, claims 11 to 1
In the invention of any one of 3 above, the oscillation output end of the oscillation circuit is connected to the third electrode through an impedance element having a constant impedance value.

In the sixteenth aspect of the present invention, the eleventh to first aspects are provided.
In any one of the inventions 3 to 3, the oscillation output end of the oscillation circuit and the third electrode are coupled by the capacitance of the detection object.

In the seventeenth aspect of the present invention, the eleventh to first aspects are provided.
In the invention of any one of 3) to 3) above, the third electrode is connected to an AC stable potential of the oscillation circuit.

In the eighteenth aspect of the present invention, the first electrode and the first electrode that are opposed to the object to be detected in the metal container are surrounded by the peripheral wall of the metal container that houses the object to be detected. Between the first and second electrodes, a sensing electrode portion formed of a second electrode formed so as to surround the oscillation electrode, an oscillation circuit connecting an oscillation output of a constant frequency between the second electrode and ground. Impedance conversion circuit that outputs the voltage corresponding to the moisture content of the object to be detected and the output voltage of the impedance detection circuit is converted to a desired voltage corresponding to the moisture content and output. A water content sensor comprising an output circuit, the first electrode, the second electrode
Are divided into a plurality of electrodes of the same number, and the divided electrodes of the first electrode and the divided electrodes of the second electrode are divided into two groups corresponding to the paired electrode connection ends of the oscillation circuit, and they are different from each other. It is characterized in that the respective divided electrodes of the second electrode belonging to the group and the peripheral wall of the surrounding metal container have the same coupling capacitance.

According to a nineteenth aspect of the present invention, the first electrode and the first electrode, which are opposed to the detection target in the metal container such that the periphery is surrounded by the peripheral wall of the metal container for storing the detection target, are provided. Between the first and second electrodes, a sensing electrode portion formed of a second electrode formed so as to surround the oscillation electrode, an oscillation circuit connecting an oscillation output of a constant frequency between the second electrode and ground. Impedance conversion circuit that outputs the voltage corresponding to the moisture content of the object to be detected and the output voltage of the impedance detection circuit is converted to a desired voltage corresponding to the moisture content and output. In a water content sensor including an output circuit, the coupling capacitance between the first electrode and the surrounding peripheral wall of the metal container is equal to the coupling capacitance between the second electrode and the surrounding peripheral wall of the metal container. So that the first or And second electrodes, and wherein the connecting the impedance elements of constant impedance value between the same potential relative to the potential of the peripheral wall surrounding the metal container.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to embodiments. (Embodiment 1) In this embodiment, as shown in FIG. 1A, a circular first electrode (hereinafter referred to as a center electrode) 41 in the center is provided.
And a sensing electrode portion composed of an annular second electrode (hereinafter referred to as an outer peripheral electrode) 42 concentrically arranged so as to surround the center electrode 41, and further concentrically outside the outer peripheral electrode 42. The third electrode (hereinafter, referred to as a guard electrode) 43 arranged in a ring shape is provided.

These electrodes 41 to 43 are arranged on the inner bottom portion of the electrode case 3 made of a resin molded product as shown in FIG. 2 similarly to the above-mentioned conventional example, and are detected when used in, for example, a garbage disposal machine. It is used by fitting the outer bottom portion of the electrode case 3 into the opening of the electrode case 3 of the metal container 2 which is a raw garbage treatment tank for containing the raw garbage as an object so as to face the inside of the metal container 2.

Here, in this embodiment, the oscillation circuit 5 using the electrostatic capacitance between the center electrode 41 and the outer peripheral electrode 42 as an element for changing the oscillation frequency, as in the conventional example of FIG. A capacitance detection circuit 9 which inputs the oscillation output of the oscillation circuit 5 and outputs a DC voltage corresponding to the oscillation frequency, and an output voltage of the capacitance detection circuit 9 is converted into a desired voltage corresponding to the amount of water and is output. And an output circuit 10.
Since the configuration of the capacitance detection circuit 9 is the same as that of the conventional example shown in FIG. 29, detailed description of the configuration is omitted.

In the present embodiment configured as described above,
As shown in FIG. 1A, there is a capacitance Cd between the center electrode 41 and the outer electrode 42, which varies depending on the object to be detected, and the guard electrode 43 and the surrounding metal container 2 are grounded (X). There is a capacitance C _GE between them, and as shown in FIG. 1B, a capacitance C _OG due to the object to be detected exists between the outer peripheral electrode 42 and the guard electrode 43. Further, it is assumed that the circuit ground (Y) and the ground (X) are AC-connected by a large-capacity capacitor.

Therefore, the capacitive coupling between the outer peripheral electrode 42 and the guard electrode 43 is ensured by the object to be detected, and the outer peripheral electrode 42 is
By driving the guard electrode 43 and the guard electrode 43 in the same phase (and substantially the same CR charge / discharge waveform), an electric field is not formed between the outer electrode 42 and the guard electrode 43 driven in the same phase, and the center electrode 41 and the outer electrode It is possible to separate the electric field region formed by 42 and the electric field region formed by the guard electrode 43 and the surrounding metal container 2. Further, there is no effect on the load capacitance of the oscillator circuit 5.

(Second Embodiment) In the first embodiment, the capacitive coupling of the object to be detected is secured between the guard electrode 43 and the outer peripheral electrode 42, and both electrodes 43 and 42 are driven in the same phase. However, in the present embodiment, as shown in FIG. 3A, the oscillation output of the oscillation circuit 5 is connected to the guard electrode 43, and the addition of this connection wiring is different from the first embodiment.

Since the other construction is the same as that of the first embodiment, the arrangement of the electrode parts is not shown, and the same constituent elements are designated by the same reference numerals.

Thus, in the present embodiment, the guard electrode 43 is driven in the same phase as the outer peripheral electrode 42 by the output of the oscillation circuit 5, so that an electric field is generated between the outer peripheral electrode 42 and the guard electrode 43 driven in the same phase. Therefore, the electric field region formed by the center electrode 41 and the outer peripheral electrode 42 and the electric field region formed by the guard electrode 43 and the surrounding metal container 2 can be separated. FIG. 3B shows an equivalent circuit of FIG.

In the above embodiment, the driving state does not change depending on the water content of the object to be detected. The capacitance C _GE between the guard electrode 43 and the ground (X) serves as the load capacitance of the oscillator circuit 5. Further, the drive waveform of the outer peripheral electrode 42 is a CR charge / discharge waveform, while the drive waveform of the guard electrode 43 is the output waveform (rectangular wave) of the oscillation circuit 5. Furthermore, since capacitive coupling by the object to be detected is not used, the drive state does not change depending on the amount of water in the object to be detected.

(Third Embodiment) In the second embodiment, the oscillation circuit 5
However, in the present embodiment, as shown in FIG. 4A, the oscillation circuit 5 is connected directly to the guard electrode 43.
Is characterized in that the output of is connected via an impedance element having a constant impedance value, a capacitor C1 in the illustrated example.

Since the other structure is the same as that of the first and second embodiments, the arrangement structure of the electrode portions is not shown, and the same constituent elements are designated by the same reference numerals.

Thus, in this embodiment, the guard electrode 43 is driven in the same phase as the outer peripheral electrode 42 by the output of the oscillation circuit 5, so that an electric field is generated between the outer peripheral electrode 42 and the guard electrode 43 driven in the same phase. Therefore, the electric field region formed by the center electrode 41 and the outer peripheral electrode 42 and the electric field region formed by the guard electrode 43 and the surrounding metal container 2 can be separated. FIG. 4B shows an equivalent circuit of FIG.

In the present embodiment configured as described above,
The combined capacitance of the capacitance C _GE between the guard electrode 43 and the ground (X) and the capacitor C1 becomes the load capacitance of the oscillation circuit 5.
Further, the drive waveform of the outer peripheral electrode 42 is a CR charge / discharge waveform, while the drive waveform of the guard electrode 43 is the output waveform (rectangular wave) of the oscillation circuit 5. Further, since the capacitive coupling by the detection target is not used, the driving state does not change due to the water content of the detection target.

Here, the load capacitance of the oscillation circuit 5 is C1 << C _GE
In the case of, it can be set by the capacitance of the capacitor C1.

(Fourth Embodiment) In the first embodiment, the guard electrode 43 is connected to the outer peripheral electrode 4 by capacitive coupling by the object to be detected.
Although it is driven in the same phase as that of FIG.
As shown in (a), by connecting the guard electrode 43 and the electrode connection end of the oscillation circuit 5 connected to the outer peripheral electrode 42 via an impedance element having a constant impedance value, a capacitor C2 in the illustrated example, It is characterized in that the guard electrode 43 is driven in the same phase as the outer peripheral electrode 42.

Since the other construction is the same as that of the first embodiment, the arrangement of the electrode parts is not shown, and the same components are designated by the same reference numerals.

Thus, in the present embodiment, the guard electrode 43 is driven by the output of the oscillation circuit 5 in the same phase as the outer peripheral electrode 42, so that an electric field is generated between the outer peripheral electrode 42 and the guard electrode 43 driven in the same phase. Therefore, the electric field region formed by the center electrode 41 and the outer peripheral electrode 42 and the electric field region formed by the guard electrode 43 and the surrounding metal container 2 can be separated. FIG. 5B shows an equivalent circuit of FIG.

In the present embodiment having the above configuration, the detection pair
Since the capacitive coupling by the elephant is not used for in-phase drive, the sensing pair
The drive state does not change depending on the water content of the elephant. Also C2
≪C _GEThe coupling capacitance with the ground (X)
The capacitance of the sensor C2 can be reduced. Further embodiment
Drive waveforms of the outer peripheral electrode 42 and the guard electrode 43 in the same manner as 1.
Has the same waveform of CR charge and discharge.

(Fifth Embodiment) In the fourth embodiment, the capacitor C2 is connected between the electrode connection end of the oscillation circuit 5 which connects the outer peripheral electrode 42 and the guard electrode 43. 6 (a) is different from the fourth embodiment in that the connection is made via the buffer circuit A1.

Since other structures are the same as those of the fourth embodiment, the arrangement structure of the electrode parts is not shown, and the same constituent elements are designated by the same reference numerals.

Thus, in this embodiment, the guard electrode 43 is driven in the same phase as the outer peripheral electrode 42 by the output of the oscillation circuit 5, so that an electric field is generated between the outer peripheral electrode 42 and the guard electrode 43 driven in the same phase. Therefore, the electric field region formed by the center electrode 41 and the outer peripheral electrode 42 and the electric field region formed by the guard electrode 43 and the surrounding metal container 2 can be separated. FIG. 6B shows the equivalent circuit of FIG.

In the present embodiment having the above-mentioned configuration, the capacitive coupling by the sensing object is not used for in-phase driving, so that the driving state does not change depending on the water content of the sensing object. Further, unlike the fourth embodiment, since no capacitor is used, the influence of the capacitance C _GE between the guard electrode 43 and the ground (X) is small. Further, similar to the fourth embodiment, the drive waveforms of the outer peripheral electrode 42 and the guard electrode 43 are the same waveforms of CR charge / discharge. (Embodiment 6) In this embodiment, instead of the buffer circuit A1 in Embodiment 5, as shown in FIG. 7A, a series circuit of inverter circuits IN1 and IN2 which are even (two in the illustrated example) knot gates. Is used. FIG. 7B is an equivalent circuit of FIG.

Since the other construction is the same as that of the fifth embodiment, the arrangement construction of the electrode portions is not shown, and the same constituent elements are designated by the same reference numerals.

Thus, this embodiment also operates similarly to the fifth embodiment and has the same features. (Embodiment 7) In Embodiment 3 described above, the oscillation output of the oscillation circuit 5 is connected to the guard electrode 43 via the capacitor C1, but in this embodiment, as shown in FIG. It is characterized in that a buffer circuit A2 is connected instead of.

Since the other structures are the same as those of the third embodiment, the arrangement structure of the electrode parts is not shown, and the same components are designated by the same reference numerals.

Thus, in the present embodiment, the guard electrode 43 is driven by the output of the oscillation circuit 5 in the same phase as the outer peripheral electrode 42, so that an electric field is generated between the outer peripheral electrode 42 and the guard electrode 43 driven in the same phase. Therefore, the electric field region formed by the center electrode 41 and the outer peripheral electrode 42 and the electric field region formed by the guard electrode 43 and the surrounding metal container 2 can be separated. FIG. 8B shows an equivalent circuit of FIG.

In the present embodiment having the above configuration, the guard electrode 43 can be sufficiently driven by using the buffer circuit A2. Further, since the capacitive coupling by the detection target is not used for in-phase driving, the driving state does not change depending on the water content of the detection target. Furthermore, although the drive waveforms of the outer peripheral electrode 42 and the guard electrode 43 are different as in the third embodiment,
The drive signal level can be adjusted by the buffer circuit A2. (Embodiment 8) In this embodiment, instead of the buffer circuit A2 in Embodiment 7, as shown in FIG. 9 (a), a series circuit of inverter circuits IN1 and IN2 which are even (two in the illustrated example) knot gates. Is used. FIG. 9B is an equivalent circuit of FIG.

Since the other construction is the same as that of the seventh embodiment, the arrangement of the electrode parts is not shown, and the same constituent elements are designated by the same reference numerals.

Thus, this embodiment also operates similarly to the seventh embodiment and has the same features. (Ninth Embodiment) The first to eighth embodiments are different from the center electrode 41.
The moisture amount sensor changes the capacitance between the outer peripheral electrode 42 and the outer peripheral electrode 42, that is, the capacitance that changes depending on the water content of the detection target, to the oscillation frequency of the oscillation circuit 5. Water corresponding to the conventional example shown in FIG. 35 inserted into the inverting input terminal of the operational amplifier 11 and the output terminal of the oscillation circuit 5 of the impedance detection circuit 13 (see FIG. 32) that changes the output voltage according to the impedance Zd which is the capacitance. It is a quantity sensor.

More specifically, this embodiment is similar to Embodiments 1 to 8 in that a guard electrode 43 is provided as shown in FIG. 10A and that an oscillator circuit connected to the outer peripheral electrode 42 is provided. This is different from the conventional example in that the output terminal of No. 5 is connected to the guard electrode 43 via the buffer circuit A3.

Since the other structure is the same as that of the conventional example shown in FIG. 35, the same components are designated by the same reference numerals, and the arrangement structure of the electrode portions is the same as that of the first embodiment, and therefore the illustration thereof is omitted. Further, the capacitance between the guard electrode 43 and the ground (X) of the metal container 2 is represented by the symbol C as in the first to eighth embodiments.
_{Attach GE} .

Thus, in this embodiment, by driving the guard electrode 43 in the same phase as the outer peripheral electrode 42, no electric field is formed between the outer peripheral electrode 42 and the guard electrode 43. Therefore, the electric field region on the detection electrode portion including the center electrode 41 and the outer peripheral electrode 42, the guard electrode 43, and the surrounding metal container 2
The electric field region formed by and can be separated. Note that FIG. 10B shows the equivalent circuit of FIG.

On the other hand, through the buffer circuit A3, the influence of the capacitive load on the oscillation circuit 5 can be reduced.

It should be noted that, as shown in FIG. 11A, a parallel circuit of a plurality of buffer circuits A3 and A3 ', or as shown in FIG. 11B, a plurality of inverter circuits IN3 and IN4 each made of a knot gate.
You may use the circuit which connected in series. (Embodiment 10) This embodiment uses an impedance element (a capacitor C3 in the illustrated example) having a constant impedance value as shown in FIG. 12A instead of the buffer A3 used in the ninth embodiment. In Embodiment 9
Is different from.

Since the other structure is the same as that of the ninth embodiment, the same components are designated by the same reference numerals and the description thereof will be omitted.

Thus, in the present embodiment, the guard electrode 43
By driving the same in the same phase as the outer peripheral electrode 42, no electric field is formed between the outer peripheral electrode 42 and the guard electrode 43. Therefore, it is possible to separate the electric field region on the detection electrode portion including the center electrode 41 and the outer peripheral electrode 42 from the electric field region formed by the guard electrode 43 and the surrounding metal container 2.
12B shows an equivalent circuit of FIG. 12B.

By the way, the capacitance C3 of the capacitor C3 is
And the capacitance C _GE between the guard electrode 43 and the ground (X) of the metal container 2 is C3 <C _GE , the guard electrode 43
It is possible to reduce the coupling capacitance between the ground and the ground (X) due to the object to be detected.

Further, as shown in FIGS. 13A and 13B, the capacitance Cd of the object to be detected is used instead of the capacitor C3, and C
By setting d <C _GE , it is possible to reduce the coupling capacitance between the guard electrode 43 and the ground (X) due to the detection target. (Embodiment 11) In the present embodiment, the inverting input terminal of the operational amplifier 11 of the impedance detection circuit 13 (see FIG. 32) that changes the output voltage according to the impedance Zd which is the electrostatic capacitance is connected to the outer peripheral electrode 42 to oscillate. The prior art shown in FIG. 36 in which the output end of the circuit 5 is connected to the center electrode 41 and the electrostatic capacitance of the detection object between the output end of the oscillation circuit 5 and the inverting input end of the operational amplifier 11 is inserted as the impedance Zd. It is a moisture sensor corresponding to an example.

More specifically, the present embodiment is similar to the ninth embodiment in that the guard electrode 43 is provided as shown in FIG. 14A and the output of the oscillation circuit 5 connected to the center electrode 41. The end is connected to the guard electrode 43 through the buffer circuit A3.
It differs from the conventional example in that it is connected to.

Since the other structure is the same as that of the conventional example of FIG. 36, the same constituent elements are designated by the same reference numerals, and the arrangement structure of the electrode portions is the same as that of the first embodiment, and therefore the illustration thereof is omitted. Further, the capacitance between the guard electrode 43 and the ground (X) of the metal container 2 is C _GE .

Thus, in the present embodiment, by driving the guard electrode 43 in the same phase as the outer peripheral electrode 42, no electric field is formed between the outer peripheral electrode 42 and the guard electrode 43. Therefore, the electric field region on the detection electrode portion including the center electrode 41 and the outer peripheral electrode 42, the guard electrode 43, and the surrounding metal container 2
The electric field region formed by and can be separated. Incidentally, FIG. 14B shows an equivalent circuit of FIG.

On the other hand, through the buffer circuit A3, the influence of the capacitive load on the oscillation circuit 5 can be reduced.

Incidentally, as shown in FIG. 15A, a parallel circuit of a plurality of buffer circuits A3 and A3 ', or as shown in FIG. 15B, a plurality of inverter circuits IN3 and IN4 each having a knot gate.
You may use the circuit which connected in series. (Embodiment 12) This embodiment uses an impedance element (a capacitor C3 in the illustrated example) having a constant impedance value as shown in FIG. 16A, instead of the buffer A3 used in the eleventh embodiment. In Embodiment 9
Is different from.

Since the other structure is the same as that of the eleventh embodiment, the same components are designated by the same reference numerals and the description thereof will be omitted.

Thus, in the present embodiment, the guard electrode 43
By driving the same in the same phase as the outer peripheral electrode 42, no electric field is formed between the outer peripheral electrode 42 and the guard electrode 43. Therefore, it is possible to separate the electric field region on the detection electrode portion including the center electrode 41 and the outer peripheral electrode 42 from the electric field region formed by the guard electrode 43 and the surrounding metal container 2.
16B shows an equivalent circuit of FIG. 16B.

By the way, the capacitance C3 of the capacitor C3 is
And the capacitance C _GE between the guard electrode 43 and the ground (X) of the metal container 2 is C3 <C _GE , the guard electrode 43
It is possible to reduce the coupling capacitance between the ground and the ground (X) due to the object to be detected.

Further, as shown in FIGS. 17A and 17B, the capacitance C4 of the detection object is used instead of the capacitor C3, and C
By setting 4 <C _GE , it is possible to reduce the coupling capacitance between the guard electrode 43 and the ground (X) due to the detection target. (Embodiment 13) In this embodiment, the inverting input terminal of the operational amplifier 11 of the impedance detection circuit 13 (see FIG. 32) for changing the amplification factor according to the impedance Zd which is the electrostatic capacity is connected to the outer peripheral electrode 42 to perform the operation. The moisture corresponding to the conventional example shown in FIG. 34 in which the output end of the amplifier 11 is connected to the center electrode 41 and the capacitance of the detection object between the inverting input end and the output end of the operational amplifier 11 is inserted as the impedance Zd. It is a quantity sensor.

More specifically, this embodiment is similar to the ninth embodiment in that a guard electrode 43 is provided as shown in FIG. 18A, and that an impedance element consisting of a resistor is provided at the inverting input terminal of the operational amplifier 11. This is different from the conventional example in that the output terminal of the oscillation circuit 5 connected via Z ₀ is connected to the guard electrode 43 via the buffer circuit A3.

Since the other structure is the same as that of the conventional example of FIG. 34, the same components are designated by the same reference numerals, and the arrangement structure of the electrode portions is the same as that of the first embodiment, and therefore the illustration thereof is omitted. Further, the capacitance between the guard electrode 43 and the ground (X) of the metal container 2 is C _GE .

Thus, in the present embodiment, by driving the guard electrode 43 in the same phase as the outer peripheral electrode 42, no electric field is formed between the outer peripheral electrode 42 and the guard electrode 43. Therefore, the electric field region on the detection electrode portion including the center electrode 41 and the outer peripheral electrode 42, the guard electrode 43, and the surrounding metal container 2
The electric field region formed by and can be separated. Note that FIG. 18B shows an equivalent circuit of FIG.

On the other hand, through the buffer circuit A3, the influence of the capacitive load on the oscillation circuit 5 can be reduced.

A parallel circuit of a plurality of buffer circuits A and A3 'as shown in FIG. 19A or a circuit in which a plurality of inverter circuits IN3 and IN4 each having a knot gate are connected in series is used as shown in FIG. 19B. May be. (Embodiment 14) The present embodiment uses an impedance element (a capacitor C3 in the illustrated example) having a constant impedance value as shown in FIG. 20A, instead of the buffer A3 used in the thirteenth embodiment. In Embodiment 9
Is different from.

Since the other structure is the same as that of the thirteenth embodiment, the same components are designated by the same reference numerals and the description thereof will be omitted.

Thus, in the present embodiment, the guard electrode 43
By driving the same in the same phase as the outer peripheral electrode 42, no electric field is formed between the outer peripheral electrode 42 and the guard electrode 43. Therefore, it is possible to separate the electric field region on the detection electrode portion including the center electrode 41 and the outer peripheral electrode 42 from the electric field region formed by the guard electrode 43 and the surrounding metal container 2.
20 (b) shows an equivalent circuit of FIG. 20 (b).

Here, the capacitance C3 of the capacitor C3,
By setting the capacitance C _GE between the guard electrode 43 and the ground (X) of the metal container 2 to be C3 <C _GE , the coupling capacitance between the guard electrode 43 and the ground (X) due to the detection target is reduced. be able to.

Further, as shown in FIGS. 21A and 21B, the capacitance Cd of the object to be detected is used instead of the capacitor C3, and C
By setting d <C _GE , it is possible to reduce the coupling capacitance between the guard electrode 43 and the ground (X) due to the detection target. (Fifteenth Embodiment) In the present embodiment, the inverting input terminal of the operational amplifier 11 of the impedance detection circuit 13 (see FIG. 32) that changes the amplification factor according to the impedance Zd that is the electrostatic capacitance is connected to the center electrode 41 to perform the operation. The moisture corresponding to the conventional example shown in FIG. 33 in which the output end of the amplifier 11 is connected to the outer peripheral electrode 42 and the capacitance of the object to be detected between the inverting input end and the output end of the operational amplifier 11 is inserted as the impedance Zd. It is a quantity sensor.

More specifically, this embodiment is similar to the ninth embodiment in that a guard electrode 43 is provided as shown in FIG. 22A, and that an impedance element consisting of a resistor is provided at the inverting input terminal of the operational amplifier 11. This is different from the conventional example in that the output terminal of the oscillation circuit 5 connected via Z ₀ is connected to the guard electrode 43 via the buffer circuit A3.

Since other configurations are the same as those of the conventional example of FIG. 33, the same reference numerals are given to the same components, and the arrangement configuration of the electrode portions is the same as that of the first embodiment, and therefore the illustration is omitted. Further, the capacitance between the guard electrode 43 and the ground (X) of the metal container 2 is C _GE .

Thus, in this embodiment, by driving the guard electrode 43 in the same phase as the outer peripheral electrode 42, no electric field is formed between the outer peripheral electrode 42 and the guard electrode 43. Therefore, the electric field region on the detection electrode portion including the center electrode 41 and the outer peripheral electrode 42, the guard electrode 43, and the surrounding metal container 2
The electric field region formed by and can be separated. 22 (b) shows an equivalent circuit of FIG. 22 (b).

On the other hand, through the buffer circuit A3, the influence of the capacitive load on the oscillation circuit 5 can be reduced.

Note that, as shown in FIG. 23A, a plurality of buffer circuits A3 and A3 'are connected in parallel, or as shown in FIG.
A circuit in which N4 is connected in series may be used. (Embodiment 16) The present embodiment uses an impedance element (a capacitor C3 in the illustrated example) having a constant impedance value as shown in FIG. 24A, instead of the buffer A3 used in the fifteenth embodiment. In Embodiment 9
Is different from.

Since the other structure is the same as that of the thirteenth embodiment, the same components are designated by the same reference numerals and the description thereof will be omitted.

Thus, in the present embodiment, the guard electrode 43
By driving the same in the same phase as the outer peripheral electrode 42, no electric field is formed between the outer peripheral electrode 42 and the guard electrode 43. Therefore, it is possible to separate the electric field region on the detection electrode portion including the center electrode 41 and the outer peripheral electrode 42 from the electric field region formed by the guard electrode 43 and the surrounding metal container 2.
Incidentally, FIG. 24 (b) shows an equivalent circuit of FIG. 24 (b).

By the way, the capacitance C3 of the capacitor C3 is
And the capacitance C _GE between the guard electrode 43 and the ground (X) of the metal container 2 is C3 <C _GE , the guard electrode 43
It is possible to reduce the coupling capacitance between the ground and the ground (X) due to the object to be detected.

Further, as shown in FIGS. 25A and 25B, the capacitance Cd of the object to be detected is used instead of the capacitor C3, and C
By setting d <C _GE , it is possible to reduce the coupling capacitance between the guard electrode 43 and the ground (X) due to the detection target. (Embodiment 17) This embodiment is designed to enable stable operation even when the grounding conditions and the like change in correspondence with the conventional example shown in FIG. It is characterized in that the guard electrode 43 is provided and the guard electrode 43 is connected to an AC stable potential, that is, the ground (G) as shown in FIG.

In the figure, 2 is a metal container, (X) is the grounding of the metal container, and C _X is the capacitance between the outer peripheral electrode 42 and the guard electrode 43.

Thus, in this embodiment, the guard electrode 43 connected to an AC stable potential is arranged as an electrode, and the electrode portion is selected depending on the connection state between the outer peripheral electrode 42 and the guard electrode 43 which constitute the detection electrode. The characteristics can be stabilized irrespective of the condition of the metal container 2 around (such as the grounding condition). (Embodiment 18) In each of Embodiments 1 to 17 described above, the guard electrode 43 is provided, but in this embodiment, as shown in FIG. 27, a plurality of center electrodes 41 and outer peripheral electrodes 42 are provided in the same number. The divided electrode of the center electrode 41 is divided into two groups 41a and 41b, and the divided electrode of the outer peripheral electrode 42 is divided into
a divided electrode 42a and a divided electrode 41b parallel to a, respectively.
And a group of divided electrodes 41a, 42a and a group of divided electrodes 41b, 42b are respectively connected to one of the paired electrode connection ends of the oscillation circuit 5, and one group is divided into two groups. Outer peripheral electrode 42a
And a coupling capacitance C _Y1 between the surrounding metal container 2 and the ground (X),
The characteristic is that the coupling capacitance C _Y2 between the outer peripheral electrode 42b of the other group and the ground (X) of the surrounding metal container 2 is made equal. Although illustration of the capacitance detection circuit and the output circuit is omitted in the figure, it goes without saying that these circuits are provided.

Thus, in this embodiment, the electrodes 41, 42 are
It is possible to reduce the occurrence of a detection error caused by the imbalance of the coupling capacitance between the metal container 2 and the ground (X) of the surrounding metal container 2. (Embodiment 19) In this embodiment, as shown in FIG. 28, the coupling capacitance C _OE between the center electrode 41 and the surrounding metal container 2 is equal to the coupling capacitance C _CE between the outer peripheral electrode 42 and the surrounding metal container 2. As described above, the feature is that an impedance element (capacitor C4 in the illustrated example) having a constant impedance value is added to the same potential of one electrode (the central electrode 41 in the illustrated example) and the surrounding metal container 2. . Although illustration of the capacitance detection circuit and the output circuit is omitted in the figure, it goes without saying that these circuits are provided.

Thus, also in this embodiment, the first embodiment
As in the case of 8, it is possible to reduce the occurrence of a detection error caused by the imbalance of the coupling capacitance between the electrodes 41 and 42 and the surrounding metal container 2.

[0103]

According to the first aspect of the present invention, the first electrode and the first electrode that are opposed to the object to be detected in the metal container are surrounded by the peripheral wall of the metal container that houses the object to be detected. From the oscillation frequency of the oscillation circuit, a detection electrode portion formed by a second electrode formed so as to surround the electrode, an oscillation circuit whose oscillation frequency changes by the capacitance between the first and second electrodes, Moisture composed of a capacitance detection circuit for converting and outputting a voltage according to the amount of water of the object to be detected and an output circuit for converting the output voltage of the capacitance detection circuit into a desired voltage according to the amount of water and outputting the voltage. The quantity sensor includes a third electrode arranged so as to surround the periphery of the detection electrode portion, and drives the third electrode and the second electrode in the same phase, so that the third electrode driven in the same phase is used. No electric field is formed between the second electrode and the third electrode, so that the first It is possible to separate the electric field region formed by the pole and the second electrode from the electric field region formed by the third electrode and the surrounding metal container, and as a result, capacitive coupling between the detection electrode portion and the metal container. Can be reduced, the influence on the operating characteristics of the oscillation circuit can be eliminated, and the error in the sensor output can be reduced.

According to a second aspect of the present invention, in the first aspect of the present invention, the driving of the third electrode and the second electrode in the same phase is performed by capacitive coupling by the detection object. It is possible to realize a moisture sensor having the above effect with a simple circuit configuration, without affecting the oscillation circuit.
The drive waveforms of the electrode and the third electrode can be substantially the same.

According to a third aspect of the invention, in the first aspect of the invention, the driving of the third electrode and the second electrode in the same phase is performed, and the oscillation output end of the oscillation circuit is connected to the third electrode. By doing so, it is possible to realize a moisture content sensor having the effect of the invention of claim 1 with a simple circuit configuration, and in particular, the driving state does not change depending on the moisture content of the object to be detected, and stable operation can be obtained.

According to a fourth aspect of the present invention, in the first aspect, the third electrode and the second electrode are driven in phase with each other between the output end of the oscillation circuit and the third electrode. Since the connection is performed through an impedance element having a constant impedance value, the water content sensor having the effect of the invention of claim 1 can be realized with a simple circuit configuration, and in particular, the drive state depends on the water content of the detection target. It does not fluctuate, stable operation is obtained, and the load capacitance of the oscillation circuit can be set by using the impedance element as a capacitor.

According to a fifth aspect of the present invention, the first aspect of the invention is to drive the third electrode and the second electrode in the same phase, and to connect the second electrode to the electrode connection end of the oscillation circuit. And the third electrode are connected by an impedance element having a constant impedance value, whereby a moisture sensor having the effect of the invention of claim 1 can be realized with a simple circuit configuration, and in particular, The driving state does not change depending on the amount of water in the object to be detected, stable operation is obtained, and by using the impedance element as a capacitor, the coupling capacitance between the third electrode and the ground of the metal container can be reduced.

According to a sixth aspect of the invention, in the first aspect of the invention, the electrode connection end of the oscillation circuit for connecting the driving of the third electrode and the second electrode in the same phase to the second electrode. Since the connection is made between the third electrode and the third electrode via a buffer circuit, it is possible to realize a moisture content sensor having the effect of the invention of claim 1 with a simple circuit configuration, and particularly the third electrode.
Electrode can be sufficiently driven, the driving state does not change depending on the water content of the object to be detected, stable operation can be obtained, and the influence of the coupling capacitance between the third electrode and the ground of the metal container is small. Further, the drive waveforms of the second electrode and the third electrode can be made substantially the same.

According to a seventh aspect of the invention, in the first aspect of the invention, the electrode connection end of the oscillation circuit is connected to drive the third electrode and the second electrode in the same phase to the second electrode. Since the third electrode and the third electrode are connected via an inverter circuit, the same effect as the invention of claim 6 is obtained.

According to an eighth aspect of the invention, in the first aspect of the invention, the driving of the third electrode and the second electrode in the same phase is performed by the oscillation output end of the oscillation circuit and the third electrode. Since it is done by connecting between the two via a buffer circuit,
It is possible to realize a moisture sensor having the effect of the invention of claim 1 with a simple circuit configuration, and particularly to sufficiently drive the third electrode,
In addition, the drive state does not change depending on the water content of the detection target,
Stable operation is obtained, the influence of the coupling capacitance between the third electrode and the ground of the metal container is small, and the signal level for driving can be adjusted.

According to a ninth aspect of the present invention, in the first aspect of the invention, the driving of the third electrode and the second electrode in the same phase is performed by the oscillation output end of the oscillation circuit and the third electrode. Since the connection is made by connecting the two via an inverter circuit, the same effect as the invention of claim 8 can be obtained.

According to a tenth aspect of the present invention, the first electrode and the first electrode which are opposed to the object to be detected in the metal container are surrounded by the peripheral wall of the metal container which houses the object to be detected. Between the first and second electrodes, a sensing electrode portion formed of a second electrode formed so as to surround the oscillation electrode, an oscillation circuit connecting an oscillation output of a constant frequency between the second electrode and ground. Impedance conversion circuit that outputs the voltage corresponding to the moisture content of the object to be detected and the output voltage of the impedance detection circuit is converted to a desired voltage corresponding to the moisture content and output. A water content sensor including an output circuit includes a third electrode arranged so as to surround the detection electrode portion, and the third electrode and the second electrode are driven in the same phase. , A second power source driven in phase Since an electric field is not formed between the third electrode and the third electrode, an electric field region formed by the first electrode and the second electrode and an electric field region formed by the third electrode and the surrounding metal container are formed. They can be separated, and as a result, variations in sensor output can be eliminated.

According to an eleventh aspect of the invention, in the invention of the tenth aspect, since the oscillation output end of the oscillation circuit is connected to the first electrode, a moisture content sensor having the effect of the tenth aspect of the invention is provided. realizable.

According to a twelfth aspect of the invention, in the tenth aspect of the invention, the oscillation output end of the oscillation circuit is connected to the second electrode through a known impedance element.
It is possible to realize a moisture content sensor that achieves the effect of the invention of claim 10, and by configuring the impedance element with a capacitor, the coupling capacitance between the third electrode and the metal container is set to the capacitance value of the detection target. It becomes possible to reduce.

According to a thirteenth aspect of the invention, in the tenth aspect of the invention, the oscillation output end of the oscillation circuit is connected to the first electrode through a known impedance element.
It is possible to realize a moisture content sensor that achieves the effect of the invention of claim 10, and by configuring the impedance element with a capacitor, the coupling capacitance between the third electrode and the metal container is set to the capacitance value of the detection target. It becomes possible to reduce.

The invention of claim 14 is based on claims 11 to 13.
In any one of the inventions, the oscillation output end of the oscillation circuit is connected to the third output circuit via a buffer circuit or an inverter circuit.
Since it is connected to the electrode of No. 3, it is possible to realize a moisture content sensor having the effect of the invention of claim 10 and to reduce the influence of the capacitive load on the oscillation circuit.

The invention of claim 15 is based on claims 11 to 13.
10. The invention according to claim 10, wherein the oscillation output end of the oscillation circuit is connected to the third electrode via an impedance element having a constant impedance value.
Can realize a moisture content sensor having the effect of the invention described above, and further reduce the coupling capacitance between the third electrode and the metal container to a capacitance value of the detection target by configuring the impedance element with a capacitor. In addition, the impedance of the impedance detection circuit can be increased by adjusting the pole newly generated by the resistance, the installation of the metal container, and the coupling capacitance between the third electrode by having a resistance in the impedance element. Can be stabilized.

The invention of claim 16 is based on claims 11 to 13.
In any of the inventions described above, since the third electrode and the second electrode are capacitively coupled by the detection object, it is possible to realize a moisture content sensor having the effect of claim 10 and further, It is possible to reduce the coupling capacitance between the electrode and the metal container to the capacitance value of the detection target.

The invention of claim 17 is based on claims 11 to 13.
In any one of the inventions, since the third electrode is connected to an AC stable potential of the oscillation circuit, the operating characteristics can be improved without being affected by the conditions such as the grounding conditions of the surrounding metal container. It can be stabilized and the error in the sensor output can be reduced.

According to the eighteenth aspect of the present invention, there is provided a first electrode, which is opposed to the object to be detected in the metal container such that the circumference is surrounded by the peripheral wall of the metal container which houses the object to be detected, and the first electrode. Between the first and second electrodes, a sensing electrode portion formed of a second electrode formed so as to surround the oscillation electrode, an oscillation circuit connecting an oscillation output of a constant frequency between the second electrode and ground. Impedance conversion circuit that outputs the voltage corresponding to the moisture content of the object to be detected and the output voltage of the impedance detection circuit is converted to a desired voltage corresponding to the moisture content and output. In a water content sensor including an output circuit, the first electrode and the second electrode are divided into a plurality of equal parts, and the first electrode and the second electrode are divided into a plurality of electrodes corresponding to the pair of electrode connection ends of the oscillation circuit. Electrode and second electrode split voltage Are divided into two groups, and the divided capacities of the second electrodes belonging to different groups from each other and the peripheral wall of the surrounding metal container are made equal, so that the metal containers around each electrode are It is possible to eliminate the imbalance of the coupling capacitance, thereby stabilizing the operating characteristics, reducing the error in the sensor output, and realizing the water content sensor in which the third electrode is unnecessary.

According to a nineteenth aspect of the present invention, a first electrode and a first electrode that are opposed to the object to be detected in the metal container are surrounded by the peripheral wall of the metal container that houses the object to be detected. Between the first and second electrodes, a sensing electrode portion formed of a second electrode formed so as to surround the oscillation electrode, an oscillation circuit connecting an oscillation output of a constant frequency between the second electrode and ground. Impedance conversion circuit that outputs the voltage corresponding to the moisture content of the object to be detected and the output voltage of the impedance detection circuit is converted to a desired voltage corresponding to the moisture content and output. In a water content sensor including an output circuit, the coupling capacitance between the first electrode and the surrounding peripheral wall of the metal container is equal to the coupling capacitance between the second electrode and the surrounding peripheral wall of the metal container. So that the first or the first Since an impedance element with a constant impedance value is connected between the electrode of and the same potential as the potential of the peripheral wall of the surrounding metal container, the imbalance of the coupling capacitance between the metal container around each electrode and Therefore, it is possible to stabilize the operation characteristics, reduce the error in the sensor output, and realize the water content sensor in which the third electrode is unnecessary.

[Brief description of drawings]

FIG. 1A is a schematic circuit configuration diagram of a main part of a first embodiment of the present invention. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 2 is a schematic cross-sectional view of a main part showing an arrangement state of the detection electrode section of the above.

FIG. 3A is a schematic circuit configuration diagram of a main part of a second embodiment of the present invention. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 4A is a schematic circuit configuration diagram of a main part of a third embodiment of the present invention. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 5A is a schematic circuit configuration diagram of a main part of a fourth embodiment of the present invention. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 6A is a schematic circuit configuration diagram of a main part of a fifth embodiment of the present invention. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 7A is a schematic circuit configuration diagram of a main part of a sixth embodiment of the present invention. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 8A is a schematic circuit configuration diagram of a main part of a seventh embodiment of the present invention. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 9A is a schematic circuit configuration diagram of a main part of an eighth embodiment of the present invention. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 10A is a schematic circuit configuration diagram of a main part of a ninth embodiment of the present invention. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 11A is a circuit configuration diagram of a main part of another example of the above. FIG. 7B is a circuit configuration diagram of a main part of another example of the above.

FIG. 12A is a schematic circuit configuration diagram of a main part of an example of a tenth embodiment of the present invention. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 13A is a schematic circuit configuration diagram of a main part of another example of the above. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 14A is a schematic circuit configuration diagram of a main part of an eleventh embodiment of the present invention. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 15A is a circuit configuration diagram of a main part of another example of the above. FIG. 7B is a circuit configuration diagram of a main part of another example of the above.

FIG. 16A is a schematic circuit configuration diagram of a main part of an example of a twelfth embodiment of the present invention. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 17A is a schematic circuit configuration diagram of a main part of another example of the above. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 18A is a schematic circuit configuration diagram of a main part of a thirteenth embodiment of the present invention. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 19A is a circuit configuration diagram of a main part of another example of the above. FIG. 7B is a circuit configuration diagram of a main part of another example of the above.

FIG. 20A is a schematic circuit configuration diagram of a main part of an example of a fourteenth embodiment of the present invention. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 21A is a schematic circuit configuration diagram of a main part of another example of the above. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 22A is a schematic circuit configuration diagram of a main part of a fifteenth embodiment of the present invention. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 23A is a circuit configuration diagram of a main part of another example of the above. FIG. 7B is a circuit configuration diagram of a main part of another example of the above.

FIG. 24A is a schematic circuit configuration diagram of a main part of an example of a sixteenth embodiment of the present invention. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 25A is a schematic circuit configuration diagram of a main part of another example of the above. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 26 is a circuit configuration diagram of a main part according to a seventeenth embodiment of the present invention.

FIG. 27 is a circuit configuration diagram of essential parts of an eighteenth embodiment of the present invention.

FIG. 28 is a circuit configuration diagram of a main part according to a nineteenth embodiment of the present invention.

FIG. 29 is a circuit configuration diagram of a conventional example.

FIG. 30 is an equivalent circuit diagram of a main part of the above.

FIG. 31 is a water content of a detection target when the same as above is used,
It is a graph which shows the relationship with the oscillation frequency of an oscillation circuit.

FIG. 32 is a circuit configuration diagram of another conventional example.

FIG. 33A is a schematic circuit configuration diagram of a main part of still another conventional example. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 34A is a schematic circuit configuration diagram of a main part of another conventional example. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 35A is a schematic circuit configuration diagram of a main part of still another conventional example. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 36A is a schematic circuit configuration diagram of a main part of still another conventional example. (B) is an equivalent circuit diagram of the main part of the same.

FIG. 37 is a schematic circuit configuration diagram of a main part of another conventional example.

[Explanation of symbols]

2 Metal container 41 Center electrode 42 Outer peripheral electrode 43 Guard electrode 5 Oscillation circuit (X) Grounding (Y) Circuit ground Cd Capacitance between center electrode and outer peripheral electrode due to sensing object C _{GE Between} guard electrode and grounding of metal container Capacitance C _OG Coupling capacitance between outer electrode and guard electrode

Continued front page    (72) Inventor Fumikazu Kurihara             1048, Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd.             Inside the company F-term (reference) 2G060 AA20 AC01 AF06 AF10 AG08                       AG10 FA01 HA02 HC10                 5J050 AA37 AA48 BB22 CC00 EE34                       EE36 FF30

Claims (19)

[Claims] 1. A first electrode, which is opposed to the object to be detected in the metal container in such a manner that the periphery is surrounded by the peripheral wall of the metal container that houses the object to be detected, and the first electrode is formed so as to surround the first electrode. A detection electrode section composed of a second electrode, an oscillation circuit whose oscillation frequency changes due to the electrostatic capacitance between the first and second electrodes, and an oscillation frequency of the oscillation circuit to determine the water content of the detection target. A moisture amount sensor including a capacitance detection circuit for converting the output voltage to a corresponding voltage and outputting the same, and an output circuit for converting the output voltage of the capacitance detection circuit to a desired voltage according to the moisture amount and outputting the voltage. A water content sensor, comprising a third electrode arranged so as to surround the periphery of, and driving the third electrode and the second electrode in the same phase. 2. A water content sensor according to claim 1, wherein the third electrode and the second electrode are driven in phase with each other by capacitive coupling by the object to be detected. 3. The in-phase driving of the third electrode and the second electrode is performed by connecting an oscillation output end of the oscillation circuit to the third electrode. The moisture sensor described. 4. In-phase driving of the third electrode and the second electrode is connected between the output end of the oscillation circuit and the third electrode via an impedance element having a constant impedance value. The moisture amount sensor according to claim 1, wherein the moisture amount sensor is performed by 5. The same-phase driving of the third electrode and the second electrode is performed with a constant distance between the electrode connection end of the oscillation circuit connecting the second electrode and the third electrode. The water content sensor according to claim 1, wherein the water content sensor is connected by an impedance element having an impedance value. 6. A buffer circuit for driving the third electrode and the second electrode in the same phase between the electrode connection end of the oscillation circuit connected to the second electrode and the third electrode. The water content sensor according to claim 1, wherein the water content sensor is connected to the water content sensor. 7. An inverter circuit for driving the third electrode and the second electrode in phase with each other between the electrode connection end of the oscillation circuit connected to the second electrode and the third electrode. 2. The process is performed by connecting through
The moisture sensor described. 8. The in-phase driving of the third electrode and the second electrode is performed by connecting an oscillation output end of the oscillation circuit and the third electrode via a buffer circuit. The water content sensor according to claim 1, wherein the water content sensor is a water content sensor. 9. The in-phase driving of the third electrode and the second electrode is performed by connecting an oscillation output end of the oscillation circuit and the third electrode via an inverter circuit. The water content sensor according to claim 1, wherein the water content sensor is a water content sensor. 10. A first electrode, which is opposed to the object to be detected in the metal container in such a manner that the periphery is surrounded by a peripheral wall of the metal container that houses the object to be detected, and the first electrode is formed to surround the first electrode. A detection electrode portion formed of a second electrode, an oscillation circuit that connects an oscillation output of a constant frequency between the second electrode and ground, and an impedance between the first and second electrodes And an impedance detection circuit for converting the output voltage of the impedance detection circuit into a desired voltage corresponding to the amount of water and outputting the voltage. The water content sensor comprises a third electrode arranged so as to surround the periphery of the detection electrode section, and drives the third electrode and the second electrode in the same phase. Quantity sensor. 11. A moisture sensor according to claim 10, wherein an oscillation output end of the oscillation circuit is connected to the first electrode. 12. A moisture sensor according to claim 10, wherein the oscillation output end of the oscillation circuit is connected to the second electrode via a known impedance element. 13. The water content sensor according to claim 10, wherein an oscillation output end of the oscillation circuit is connected to the first electrode via a known impedance element. 14. The water content sensor according to claim 11, wherein an oscillation output end of the oscillation circuit is connected to the third electrode via a buffer circuit or an inverter circuit. 15. The oscillation output end of the oscillation circuit is connected to the third electrode through an impedance element having a constant impedance value.
14. The water content sensor according to any one of 1 to 13. 16. The water content sensor according to claim 11, wherein the oscillation output end of the oscillation circuit and the third electrode are coupled by the capacitance of the object to be detected. . 17. The method according to claim 1, wherein the third electrode is connected to an AC stable potential of the oscillator circuit.
The water content sensor according to any one of 1 to 13. 18. A first electrode, which is opposed to the object to be detected in the metal container in such a manner that the periphery is surrounded by the peripheral wall of the metal container that houses the object to be detected, and the first electrode is formed so as to surround the first electrode. A detection electrode portion formed of a second electrode, an oscillation circuit that connects an oscillation output of a constant frequency between the second electrode and ground, and an impedance between the first and second electrodes And an impedance detection circuit for converting the output voltage of the impedance detection circuit into a desired voltage corresponding to the amount of water and outputting the voltage. In the water content sensor, the first electrode and the second electrode are divided into a plurality of pieces in the same number, and the divided electrode and the second electrode in the first electrode correspond to the pair of electrode connection ends of the oscillation circuit. Split the electrodes into two glue A moisture amount sensor characterized in that each of the divided electrodes of the second electrodes belonging to different groups and the peripheral wall of the surrounding metal container have the same coupling capacitance. 19. A first electrode, which is opposed to the object to be detected in the metal container in such a manner that the periphery is surrounded by the peripheral wall of the metal container for housing the object to be detected, and the first electrode is formed so as to surround the first electrode. A detection electrode portion formed by a second electrode, an oscillation circuit connecting an oscillation output of a constant frequency between the second electrode and ground, and an impedance between the first and second electrodes are amplified. And an impedance detection circuit for converting the output voltage of the impedance detection circuit into a desired voltage corresponding to the amount of water and outputting the voltage. In the water content sensor, the first electrode and the surrounding peripheral wall of the metal container have a coupling capacity equal to that of the second electrode and the surrounding peripheral wall of the metal container. 1
Alternatively, a water content sensor, wherein an impedance element having a constant impedance value is connected between the second electrode and the same potential as the potential of the peripheral wall of the surrounding metal container.