JPH05232055A - Humidity detecting device - Google Patents

Abstract

PURPOSE:To obtain a humidity signal with good detecting accuracy entirely from the low-humidity side to the high-humidity side by improving a humidity detecting device so that a low-humidity side output or a high-humidity side output is not saturated even if a resistance value of a humidity sensor is changed logarithmically. CONSTITUTION:A humidity detecting circuit 3 is driven with a low impedance, a circuit network of each of a first humidity-sensitive circuit 6 and a second humidity-sensitive circuit 7 is constituted by a humidity sensor and a resistance, and values of the humidity sensors and the resistances are set so that a voltage at connecting point of the first humidity-sensitive circuit 6 and the second humiditysensitive circuit 7 becomes linear at each humidity of several points. An output from the humidity detecting circuit becomes linear from the low- humidity side to the high-humidity side, and a humidity detecting device with good detecting accuracy can be realized. Also, by constituting the circuit networks in which a resistance value of the resistance is changed relative to change in temperature in the first and the second humidity-sensitive circuits, temperature can be compensated in the humidity detecting device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidity detecting device which converts a humidity change into a voltage change and outputs it as an electric signal.

[0002]

2. Description of the Related Art There is a humidity sensor having a porous material impregnated with a polymer electrolyte. This type of humidity sensor has high sensitivity because the range of change in resistance value with respect to humidity changes significantly by 2.5 digits or more, and the range of change in resistance value is large, so changes are detected and devices such as air conditioners and humidifiers are controlled. It is convenient to do. But,
Recently, more comfortable space is required, and more optimal automatic control is required in combination with a microcomputer and a humidity detecting device. It is strongly demanded that the humidity detecting device used therein not only detect a change in humidity but also measure humidity accurately.

FIG. 11 is a block diagram showing the structure of a conventional humidity detecting device. In FIG. 12, 60 is an oscillation circuit, 61 is a humidity detection circuit, 64 is a resistance, 65 is a humidity sensor, e is an AC voltage applied to the series circuit, and 66 is an output of the humidity detection circuit 61. Reference numeral 62 indicates a rectifier circuit, and 63 indicates the output of the rectifier circuit 62.

The operation of the humidity detecting device constructed as above will be described. The humidity sensor 65 is polarized when a DC voltage is applied. Therefore, the oscillation circuit 60 generates an AC voltage, and this AC voltage is applied to the humidity detection circuit 61. The humidity detection circuit 62 is composed of a series circuit of a resistor 64 and a humidity sensor 65. In the humidity detection method, when the resistance value of the humidity sensor 65 changes according to the change in humidity, the current changes. The change in the current is detected as the change in the voltage drop of the resistor 64. If the resistance value of the resistor 64 is R, the resistance value of the humidity sensor 65 is RH, and the value of the applied voltage e is 1 for the sake of simplicity, the output 66 of the humidity detection circuit 61 is replaced with the relationship of the voltage division ratio of Expression 1. Can be shown.

Output 66 = RH / (R + RH) ... Equation 1 Furthermore, the output 66 of the humidity detection circuit 61 is converted into a DC voltage via the rectification circuit 62 and output to 63 as a detection signal. ing.

[0006]

FIG. 12 shows an example of the characteristics of a humidity sensor in which a porous material is impregnated with a polymer electrolyte, and shows the relationship between humidity and resistance value. The resistance change changes logarithmically and is not a linear change. For use in the following description, a humidity sensor in which a porous material is impregnated with a polymer electrolyte is referred to as a humidity sensor. In FIG. 12, 68 is 10 ° C. and 67 is 25 ° C.
C. and 69 indicate the case of 40.degree.

When this humidity sensor is used in the conventional humidity detecting circuit 61, the output characteristic shown in FIG. However, the case where the temperature is 25 ° C. is illustrated.
In FIG. 13, a characteristic 70 is a case where the value R of the resistor 64 is fixed to 2 k ohms, and good measurement can be made on the high humidity side where the humidity is several tens% or more. On the other hand, it has the drawback that it cannot be measured on the low humidity side, where the humidity is tens of percent or less. What can not be measured on the low humidity side is
The resistance value RH of the humidity sensor 65 becomes much larger than the value R of the resistance 64, and the voltage division ratio of the expression 1 approaches 1, so that even if the resistance value RH of the humidity sensor 65 changes,
Does not appear as a change in the terminal voltage. Characteristic 72 is resistance 64
When the value R of is fixed to 20 k ohm, the humidity can be measured well in the vicinity of several tens of percent. However, there is a drawback that the range of change in output is reduced on the low humidity and high humidity side and the resolution is reduced. The change width of the output decreases on the low humidity and high humidity side because the resistance value RH of the humidity sensor 65 decreases.
And the value R of the resistor 64 increases, the humidity sensor 65
This is because the change in the terminal voltage generated in the resistor 64 with respect to the change in the resistance value is reduced. Characteristic 71 is a case where the value R of the resistor 64 is fixed at 200 k ohms, and there is a drawback that the low humidity side can be measured but the high humidity side cannot be measured. The high humidity side cannot be measured because the resistance value RH of the humidity sensor 65 is the resistance 6
4 is much smaller than the value R of 4, and the partial pressure ratio of Equation 1 is 0.
This is because the terminal voltage of the resistor 64 does not change with respect to the change of the resistance value of the humidity sensor. Therefore,
In order to measure humidity accurately, the value R of the resistor 64 is such that the output 66 has a linear relationship as much as possible with changes in humidity.
Will need to be selected.

Here, the linearization rate is used as a method for evaluating linearity. The linearization rate is expressed by Equation 2 using the values in FIG. The linearization rate is a virtual straight line 7 for each humidity.
The ratio deviates from 2, and the larger the number, the larger the deviation. However, 73 in FIG. 14 is the output V at low humidity (30%).
Maximum value at h, 74 of FIG. 14 is output V of high humidity (90%)
l represents the minimum value. E in FIG. 14 is the difference between the outputs Vh and Vl, and ΔE connects the two points Vh and Vl on a straight line, and represents the deviation width from the virtual straight line 72.

Linearization rate = ΔE / E × 100 ... Equation 2 FIG. 15 shows the linearization rate when the resistor 64 is selected to have an appropriate resistance value R. 78 is the case where R is 20 k ohms, 76 is the case where R is 10 k ohms, and 77 is the case where R is 5 k ohms. 1
The value of the linearization rate at about 0 k ohm is smaller by about 7 to 8% than the others. By the way, the humidity sensor has a temperature characteristic as shown in FIG. In order to perform temperature correction, a thermistor whose resistance value changes with temperature is used instead of the resistor 64. Generally, at a given humidity,
A thermistor having a temperature coefficient close to that of the humidity sensor is used.
FIG. 15 shows the linearization rate of the output characteristics with respect to each temperature and humidity when the thermistor is used. FIG.
In 80, the resistance value of the thermistor is 2 at a temperature of 10 ° C.
2k ohm, 79 is 10k ohm at 25 ° C, 81 is 40
The case of the temperature characteristic of the thermistor which becomes 5 k ohm at 0 ° C. is illustrated. The spread of the linearization rate value increases depending on the temperature, and the accuracy deteriorates.

In the prior art, since the linearity of the output characteristic of the humidity detecting circuit depends on the value of the series resistance as described above, the linearity is affected if the output impedance of the oscillator circuit is high. Therefore, it is necessary to reduce the output impedance of the oscillator circuit.

In addition, even if the value of the series resistance 64 with the humidity sensor is selected as an appropriate resistance value, the resistance value is fixed with respect to the change in humidity, so that the resistance value of the humidity sensor is logarithmic. In the case of a large change of 2.5 digits or more, the linearity disappears and the linearization rate also increases. That is, the low humidity side,
Since the deviation from the virtual straight line becomes large on the high humidity side, the resolution of the output characteristic deteriorates. Further, even if the temperature correction is taken into consideration, the value of the linearization rate has a large spread, so that there is a problem in that measurement is inconvenient, such as deterioration in humidity measurement accuracy.

[0012]

In order to solve the above-mentioned problems, the present invention solves the above problems by a humidity detecting circuit for converting a humidity change into a voltage change, and a circuit for applying an AC voltage for driving the humidity detecting circuit. And a humidity detecting circuit in which a first moisture sensitive circuit and a second moisture sensitive circuit are connected in series, and a connection portion between the first moisture sensitive circuit and the second moisture sensitive circuit is provided. The first humidity sensing circuit outputs a voltage as a humidity detection voltage, and the first humidity sensing circuit is provided with a first resistance in series with a first humidity sensor whose resistance value changes according to a change in humidity, and further in parallel with the first humidity sensor. A resistor circuit network including a second resistor,
The humidity-sensing circuit is composed of a parallel circuit including a third resistance and a second humidity sensor whose resistance value changes according to a change in humidity, and a connecting portion between the first humidity-sensing circuit and the second humidity-sensing circuit. Of the first voltage so that the voltage is linear for several humidity points.
The resistance value of the humidity sensor, the first and second resistance values, the resistance value of the second humidity sensor, and the third resistance value are set.

Further, in order to perform temperature compensation of the linearity of the output, at least the first moisture-sensitive circuit described above includes a resistor whose resistance value changes with temperature change and a circuit network whose resistance value changes with humidity change. In addition to being configured by using the first humidity sensor, the first humidity sensor includes a second humidity resistor connected in series with the first humidity sensor, and a third resistor connected in parallel with the first humidity sensor. It is characterized by being composed of a circuit network.

[0014]

With the above structure, the circuit for applying an AC voltage does not depend on the impedance of the oscillation circuit,
The humidity detection circuit can be set to drive with low impedance. Then, regarding the humidity detection circuit, assuming that the resistance value of the first humidity detection circuit is ra and the resistance value of the second humidity detection circuit is rb, the output of the humidity detection circuit of the present invention is the output of the first humidity detection circuit. A change in voltage according to the voltage division ratio between the resistance value and the resistance value of the second humidity sensing circuit is output. Therefore, the output characteristic with respect to the humidity change is the voltage change of the relation of the expression 3. However,
The voltage e applied to the series circuit of the first moisture sensitive circuit and the second moisture sensitive circuit is set to 1 for simplicity.

Output = rb / (ra + rb) ... Equation 3 Here, the resistance value of the first humidity sensor is h1, the resistance value of the second humidity sensor is h2, and the resistance value of the first resistance is Let a be the value, b be the value of the second resistance, and c be the value of the third resistance, and h2≈h1 ... Equation 4 c>b> a. 5 According to the equations (4) and (5), it is possible to limit the variation of the resistance value ra of the first moisture-sensitive circuit to the variation of humidity and configure it within the range from a to b. Further, the resistance value rb of the second humidity sensing circuit can be restricted so as to change within the range from the minimum value h2 of the resistance value h2 of the second humidity sensor to c. Therefore, the variation range of the resistance value ra of the first moisture sensitive circuit is smaller than the variation range of the resistance value rb of the second moisture sensitive circuit. The resistance value ra of the first humidity sensing circuit can be set to be appropriately large on the low humidity side and appropriately small on the high humidity side.

Therefore, the resistance value of the first humidity sensing circuit and the resistance value of the second humidity sensing circuit are limited and set so that the output of the humidity sensing circuit becomes linear for each of several humidity points. Is possible.

[0017]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below.

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a detailed view of FIG. 1 and 2, 1 is an oscillation circuit, 2 is a drive circuit, 3 is a humidity detection circuit,
6 is the first moisture sensitive circuit, 7 is the second moisture sensitive circuit, e is the voltage applied to the humidity detecting circuit, 4 is the output of the humidity detecting circuit, 5
Is a rectifier circuit, and 8 is an output of the rectifier circuit. In FIG. 2, 18 and 19 of the drive circuit 2 are resistors, 17 is a differential amplifier, 20 is a capacitor, 21 of the humidity detection circuit 3 is a resistor,
22 is a humidity sensor, 23 and 24 are resistors, 25 is a humidity sensor, 26 is a resistor, 27 of the rectifier circuit 5 is a differential amplifier, 28
Is a diode, 29 is a resistor, 30 is a resistor, 31 is a capacitor, 9 is an intermediate power supply circuit, 11 is an output of the intermediate power supply circuit,
Reference numeral 10 indicates a power supply line.

The oscillator circuit 1 is used to generate an AC voltage. For example, it is composed of an astable multivibrator circuit. The drive circuit 2 has a low impedance regardless of the output impedance of the oscillation circuit 1 and is used to add the output of the oscillation circuit 1 to the humidity detection circuit 3.
The output of the drive circuit 2 divides the differential voltage of the output 11 of the intermediate power supply circuit 9 by the resistors 18 and 19, adds the output to the non-inverting input of the differential amplifier 17, adds the output to the inverting input, and further through the capacitor 20. To drive the humidity detection circuit 3. Therefore,
The resistors 18 and 19 set the amplitude of the voltage e. The capacitor 20 has a sufficiently low impedance and blocks a direct current voltage so that the humidity sensor does not polarize. The humidity detecting circuit 3 includes a first moisture sensitive circuit 6 and a second moisture sensitive circuit 7.
And a connection portion between the first moisture sensitive circuit 6 and the second moisture sensitive circuit 7 is used as the output 4 of the humidity detection circuit 3. Further, the resistor 21 is auxiliary connected to shape the applied voltage waveform on the low humidity side. The rectifier circuit 5 is used to convert the output 4 into direct current. The rectifier circuit 5 applies, for example, the output 4 to the non-inverting input of the differential amplifier 27, the output to the inverting input via the diode 28, and a direct current through a smoothing circuit including resistors 29 and 30 and a capacitor 31. It has been converted. Then, the output 4 is converted into a DC voltage by the rectifier circuit 5 and is output to the output 8 of the rectifier circuit 5,
It is used as a signal for control. When the differential amplifier circuit is operated by a single power supply, the intermediate power supply circuit 9 is provided so that a DC bias is not applied to the humidity sensor. Therefore, the AC voltage e based on the output 11 of the intermediate power supply circuit 9 is applied to the humidity detection circuit 3.

Now, the operation of the humidity detecting circuit 3 according to the present invention will be described in more detail. The first moisture sensitive circuit 6 is configured by connecting a resistor 24 in series with a parallel circuit of a humidity sensor 22 and a resistor 23. The humidity sensing circuit 7 is composed of a parallel circuit of a humidity sensor 25 and a resistor 26. The resistance value of the humidity sensor changes logarithmically as shown in FIG. Therefore, when the resistance 26 is connected in parallel with the humidity sensor 25 as in the second humidity sensing circuit 7, the upper limit value is limited. The relationship of the resistance rb is shown at 36 in FIG. However, the temperature is 25 ℃, parallel resistance 26
The case where the resistance value c of 1 is 1400 kΩ is illustrated. Next, the resistance value h1 of the humidity sensor 22 used in the first humidity sensing circuit 6 is set to be approximately the same as the resistance value h2 of the humidity sensor 25. This humidity sensor 22 and resistance 23
By connecting the resistor 24 in series with the parallel circuit of
The upper limit value and the lower limit value of the resistance value h1 can be limited. 37 of FIG.
The relationship between the humidity and the resistance value ra of the first moisture sensitive circuit 6 is shown. However, the case where the temperature is 25 ° C., the resistance value b of the parallel resistance value 23 is 700 kΩ, and the resistance value a of the series resistor 24 is 10 kΩ is illustrated. In this way, when the humidity detection circuit 3 is configured in the series circuit of the first humidity sensing circuit 6 and the second humidity sensing circuit 7 and the output 4 is obtained from the series connection portion, the output is expressed by the relation of Expression 3. Become. FIG. 4 shows the relationship between humidity and output 4. Note that FIG. 4 is a graph of the output obtained by removing the output 11 from the voltage of the output 4 in order to make the graph easier to see. Since the output 11 has a constant voltage, there is no difference in the linearization rate of the values plotted by removing the output 11. Then, the linearization rate is as shown by 38 in FIG. The value of the linearization rate is several% or less for each of several humidity ranges from low humidity to high humidity. Compared with the value close to 10% of the conventional technology,
It is even more linear. This is the second moisture sensing circuit 7
Of the first humidity sensing circuit 6 can be set so that the resistance value ra of the first humidity sensing circuit 6 is increased to a suitable value on the low humidity side and decreased to an appropriate value on the high humidity side. is there.

By the way, the linearization rate changes depending on the value C of the resistor 24. The case where the value C of the series resistor 24 is 20 kΩ is 39 in FIG. 5, and the case where the value C is 5 kΩ is 4 in FIG.
It was shown at 0. Next, the resistance value h1 of the humidity sensor 22 is shown in FIG.
The relationship between the resistance value h2 of the humidity sensor 25 and the linearization rate is shown. 41 indicates that when the resistance values h1 and h2 are almost the same,
42 is a case where the resistance value h2 is 1.25 times h1 and 43 is a case where the resistance value h2 is 0.75 times h1. in this case,
The linearization rate is good when the resistance values h1 and h2 are almost the same.

As described above, by utilizing the characteristics of the conventional humidity sensor, a humidity sensitive circuit including almost the same humidity sensor in the circuit is connected in series, and the resistance value c of the resistor 26 is changed from the resistance value b of the resistor 23. There is a condition where the linearization rate of the output of the humidity detection circuit is good for each of several humidity points by setting the resistance value a of the resistor 24 to be high and appropriately selecting the resistance value a of the resistor 24 to be smaller than the resistance value b of the resistor 23. Therefore, the linearity is improved, and the change in humidity can be accurately measured.

Further, instead of the resistor 24, a thermistor is connected in series in order to perform temperature correction of the linearization rate with respect to the temperature characteristics of the humidity sensors 22 and 25. FIG. 7 shows the temperature characteristics of the linearization rate. The temperature characteristics of the thermistor used are conventional. 44 has a temperature of 25 ° C, 45 has a temperature of 10 ° C, 4
No. 6 is when the temperature is 40 ° C. The spread of the value of the linearization rate is less than 10% as compared with the prior art, and the straight line is far better than within 10% of the prior art. First moisture sensitive circuit and second
Since the connection portion with the humidity sensing circuit is output as the humidity detection voltage, the temperature characteristics of the first and second humidity sensors act so as to moderate output changes, so that temperature correction using a thermistor with conventional characteristics is performed. However, the spread of the value of the linearization rate is smaller than that of the conventional technique, and the temperature change can be kept within 10%. By the way, when it is necessary to compensate the resistance value of the thermistor on the low temperature side and the high temperature side, a resistor may be connected in parallel or in series with the thermistor.

(Embodiment 2) As Embodiment 2, a method of constructing the humidity detecting circuit 3 is shown in FIG. 47 is a porous substrate, 4
8, 49 and 50 are electrodes, 51 and 52 are drive terminals, 53 is an output terminal, and others are the same as those in FIG.

The difference is that electrodes 48, 49 and 50 are provided on the same porous substrate 47 and impregnated with a polymer electrolyte.
Then, between the electrodes 48 and 49, the humidity sensor 22 of FIG.
And the humidity sensor 2 of FIG. 2 is formed between the electrodes 49 and 50.
Formed 5. To configure the humidity detection circuit 3, the electrode 4
8 and the electrode 49 to connect the resistor 23, the electrode 48 and the resistor 2
4 and is connected to the output of the drive circuit 2 via the drive terminal 51. On the other hand, the resistor 26 is connected between the electrode 49 and the electrode 50 and connected to the output 11 via the output terminal 53. Further, the drive terminal 52 may be provided from the electrode 49 and connected to the rectifier circuit 5.

With this structure, the humidity sensors having substantially the same structure can be easily paired, so that the temperature characteristics are the same and the variation in the linearization rate is small. Therefore, there are advantages such as improvement in measurement accuracy.

(Third Embodiment) As a third embodiment, another configuration method of the humidity detecting circuit 3 is shown in FIG. The difference is that a thermistor 55 and a resistor 56 are connected in series with a pair of humidity sensors 54. When the resistance values of the humidity sensor 54 and the thermistor 55 become extremely small on the high temperature and high humidity side outside the measurement range and it is necessary to limit the power consumption of the humidity sensor 54, a resistor 56 is connected in series with the thermistor 55.
It is possible to connect.

(Embodiment 4) As Embodiment 4, another method of forming the humidity detecting circuit 3 is shown in FIG. The difference lies in that a thermistor 58 is connected in parallel with the thermistor 58 in series with the pair of humidity sensors 54. Especially when the temperature compensation needs to be highly accurate in the range of several tens of percent of humidity, the thermistors 58 and 59 can be combined as the compensation circuit 57.

[0029]

As described above, according to the present invention, the amplitude can be set by the circuit for applying the AC voltage without being influenced by the impedance of the oscillation circuit, and the humidity detecting circuit can be driven with low impedance. Therefore, there is an advantage that linearity is not affected. Moreover, in order to improve the linearity of the output characteristic of the humidity detection circuit, a first humidity-sensitive circuit configured by a resistance circuit network of the first resistance, the second resistance, and the first humidity sensor, and further, The second humidity sensor and the second resistance circuit in which the third resistance is connected in parallel are connected in series, and the connection portion between the first humidity detection circuit and the second humidity detection circuit is output as the humidity detection voltage. It was configured to do. As a result, even if the characteristic of the conventional humidity sensor in which the resistance value changes by 2.5 digits or more with respect to the humidity change is utilized, if the first, second, and third resistance values are appropriately selected, the first It is possible to limit the change range of the resistance values of the humidity sensitive circuit and the second moisture sensitive circuit to appropriate values. Since the resistance value of the first humidity sensing circuit 6 can be set to a large value on the low humidity side and a small value on the high humidity side, the resistance value of the first humidity sensing circuit 6 can be set to a smaller value than the conventional technique for each of several humidity points. There is a good condition that the linearization rate of the output characteristic of the humidity detection circuit is within several percent. Therefore, the linearity is improved as compared with the conventional technique, and there is an advantage that the humidity change can be accurately measured. Also, the first
Since the connection between the humidity-sensitive circuit and the second humidity-sensitive circuit is output as the humidity detection voltage, the temperature characteristics of the first and second humidity sensors act so as to mitigate the output change from each other. Even with the temperature correction using the thermistor, the spread of the linearization rate value is smaller than that in the conventional technique, and it can be within 10% with respect to the temperature change. Therefore, the linearity is improved even with respect to the temperature change, and the humidity change can be accurately measured. Moreover, a simple means of converting the output 4 into a DC voltage by the rectifier circuit 5 can be used as a signal for measurement, control, etc., and has a great effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing a humidity detecting device according to an embodiment of the present invention.

FIG. 2 is a detailed diagram of a humidity detecting device according to an embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a relationship between humidity and resistance value in a first moisture sensitive circuit and a second moisture sensitive circuit used in this embodiment.

FIG. 4 is an output characteristic diagram of the humidity detection circuit according to the present embodiment under the condition that the most straight line is obtained.

FIG. 5 is a diagram showing a linearization rate of the first moisture sensitive circuit according to the present embodiment.

FIG. 6 is a diagram showing the relationship of the linearization rate when the condition of the value of the second humidity sensor is changed in the second humidity sensing circuit according to the present embodiment.

FIG. 7 is a diagram showing the relationship between temperature and linearization rate when a thermistor is used in place of resistance in the first moisture sensitive circuit according to the present embodiment.

FIG. 8 is a second embodiment showing the configuration of the humidity detecting circuit according to the present invention.

FIG. 9 is a third embodiment showing the configuration of the humidity detecting circuit according to the present invention.

FIG. 10 is a fourth diagram showing the configuration of the humidity detection circuit according to the present invention.
Examples of

FIG. 11 is a block diagram showing a conventional humidity detector.

FIG. 12 is a characteristic diagram of a humidity sensor configured by impregnating a porous material with a polymer electrolyte.

FIG. 13 is a diagram showing resistance conditions and output characteristics of a conventional humidity detection circuit.

FIG. 14 is a diagram for explaining the linearization rate.

FIG. 15 is a diagram showing the relationship between the resistance condition and the linearization rate of the conventional humidity detection circuit.

FIG. 16 is a diagram showing the relationship between temperature and linearization rate when a thermistor is used instead of the resistance of the conventional humidity detection circuit.

[Explanation of Codes] 1 Oscillation circuit 2 Drive circuit 3 Humidity detection circuit 4 Output 6 First humidity sensing circuit 7 Second moisture sensing circuit 21 Resistance 22 Humidity sensor 23 Resistance 24 Resistance 25 Humidity sensor 26 Resistance

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryoichi Makimoto 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Hiromitsu Taki 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A humidity detecting circuit for converting a humidity change into a voltage change, and a circuit for applying an AC voltage for driving the humidity detecting circuit, wherein the humidity detecting circuit includes a first humidity sensing circuit and a first humidity sensing circuit. 2 humidity-sensitive circuits are connected in series, and the voltage at the connection between the first humidity-sensitive circuit and the second humidity-sensitive circuit is output as a humidity detection voltage, and the first humidity-sensitive circuit outputs humidity. The first humidity sensor whose resistance value changes due to the change is connected in series with the first humidity sensor.
And a second resistance in parallel with the first humidity sensor, and the second humidity sensing circuit has a third resistance and a resistance value that changes according to a change in humidity. It is configured by a parallel circuit with a second humidity sensor, and the voltage at the connecting portion between the first humidity sensing circuit and the second moisture sensing circuit is linear for several humidity points. A humidity detecting device, wherein the resistance value of the first humidity sensor, the first and second resistance values, the resistance value of the second humidity sensor, and the third resistance value are set. 2. The first moisture-sensitive circuit according to claim 1, wherein at least a resistance whose resistance value changes with temperature change and a circuit network whose resistance value changes with humidity change are used.
The humidity detection device described. 3. A first humidity-sensing circuit connects a second humidity resistor and a third resistor in series with the first humidity sensor, and further comprises a third resistor connected in parallel with the first humidity sensor. The humidity detecting apparatus according to claim 2, wherein the humidity detecting apparatus is configured by the following network.