JP3060243B2 - Humidity detector - Google Patents

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 for detecting the humidity inside a room or inside a dryer.

[0002]

2. Description of the Related Art In recent years, automatic control using humidity sensors has been performed from industrial air conditioners to small home appliances such as copiers, air conditioners and humidifiers. Accordingly, there is a demand for a humidity detection device that can cover a wide humidity range with high accuracy.

Hereinafter, a conventional humidity detecting device will be described. As a conventional electric resistance type humidity sensing element, one utilizing change in proton conductivity on the surface of a metal oxide, one utilizing change in the degree of ionic dissociation of a polymer electrolyte, one utilizing electron conduction at a high temperature of a ceramic semiconductor, There is a method using a change in electron conductivity of a water-absorbing polymer in which carbon powder is dispersed.

[0004] Among them, those utilizing proton conduction of metal oxides have the advantages of high heat resistance, resistance to adhered dirt, and the ability to detect a wide range of humidity. The voltage is limited to alternating current, which causes a great cost disadvantage in the control circuit. Further, in order to prevent the drift phenomenon of the change in the resistance value with respect to the change in the humidity, a troublesome work of heating and cleaning is required.

[0005] A polymer electrolyte utilizing ionic conductivity does not require heat cleaning, but the applied voltage is limited to alternating current because the conductive species is ions.

In the case of ceramic semiconductors using electronic conduction, a direct current can be generally used. However, since driving is performed only at a high temperature of 400 ° C. or more, the semiconductor is substantially driven to prevent diffusion of electrode materials at a high temperature. Need to apply an alternating current.

[0007] On the other hand, a device using electron conductivity of a water-absorbing polymer in which carbon powder is dispersed can be driven by a direct current. It is not possible to detect a wide range of humidity changes.

FIG. 5 shows a conventional humidity detecting method using a moisture-sensitive element in which carbon powder is dispersed in a water-absorbing polymer. 1 is a DC power supply of 1V, 2 is a humidity sensitive element, 3 is a fixed resistor having a resistance of 100Ω connected in series to the humidity sensitive element 2 in order to take out a change in the resistance of the humidity sensitive element as a voltage change. This is an output terminal for extracting a voltage change.

[0009] With respect to the conventional example configured as described above,
The operation will be described below. First, a change in the humidity of the atmosphere causes a change in volume of the water-absorbing polymer of the moisture-sensitive element 2 such as swelling or contraction, and the contact distance of carbon particles inside the water-absorbing polymer changes. The change in the contact distance results in a change in the resistance value of the moisture-sensitive element. Of the power supply voltages applied to both ends of the humidity sensing element 2 and the fixed resistor 3, a divided voltage corresponding to the ratio of the two resistance values is obtained from the output terminal 4, and the output voltage with respect to the humidity obtained by the humidity detecting device is obtained. The characteristics are as shown in FIG.

[0010]

However, in the above-described conventional configuration, the resistance value of the humidity sensing element 2 with respect to a change in humidity rapidly increases at a specific humidity or higher, so that the output voltage also rapidly rises, and therefore, a wide humidity range. There was a problem that the range could not be measured accurately.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a humidity detecting device which operates with direct current and has a wide humidity detecting range.

[0012]

In order to achieve the above-mentioned object, a humidity detecting device according to the present invention comprises a plurality of humidity-sensitive elements having different resistance values with respect to a change in humidity connected in series, and the humidity-sensing element has Each has a configuration in which resistors each having a unique resistance value are connected in parallel. Then, a humidity signal corresponding to the combined resistance value is extracted.

[0013]

According to the above configuration, since the output voltage changes gradually over a wide humidity range, it is possible to detect humidity in a wide area. In addition, direct current can be applied by using a moisture-sensitive element in which conductive powder is dispersed in a water-absorbing polymer.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments will be described below in detail with reference to the drawings. FIG. 1 shows a humidity detecting device according to an embodiment of the present invention. Reference numerals 5 to 10 denote humidity-sensitive elements having different resistance value changes with respect to humidity changes, which are connected in series. 11-16
Are resistors each having a specific resistance value,
10 are connected in parallel. The resistance value of resistor 11 is 500Ω, the resistance value of resistor 12 is 800Ω,
Is 1100Ω, the resistor 14 has a resistance value of 1400Ω, the resistor 15 has a resistance value of 1700Ω, and the resistor 16 has a resistance value of 2000Ω. In each case, a fixed resistor is used.

Each of the moisture sensitive elements 5 to 10 has a structure in which a moisture sensitive material obtained by decomposing a conductive powder into a water-absorbing polymer is applied to an Ag comb electrode on an alumina substrate. Here, carbon powder is used as the conductive powder. In addition,
The conductive powder is not limited to the carbon powder, but may be a metal powder such as Au or Pt or a metal oxide powder such as RuO ₂ . As the water-absorbing polymer, a copolymer of 2-hydroxyethyl methacrylate and glycidyl methacrylate is used, and a strong film that is not affected by water, gas, or the like by thermal crosslinking is formed. The moisture-sensitive property of the moisture-sensitive element is determined by the ratio of the carbon powder to the water-absorbing polymer. The weight ratio of the carbon powder to the water-absorbing polymer in the moisture-sensitive element 5 was 10%.
Is 20%, the humidity-sensitive element 7 is 40%, the humidity-sensitive element 8 is 60%, the humidity-sensitive element 9 is 80%, and the humidity-sensitive element 10 is 90%.

Reference numeral 3 denotes a resistor for extracting a change in the resistance value of these moisture-sensitive elements as a divided voltage output. A fixed resistor having a resistance value of 2000Ω is used. The resistance is not limited to a fixed resistor, but a thermistor for temperature compensation can be used. Reference numeral 1 denotes a 1 V DC power supply, and 4 denotes an output terminal.

The operation of the humidity detecting device according to the present embodiment having the above-described configuration will be described below. First, since the water-absorbing polymer is in a contracted state in a low humidity state, the inside of the carbon particles is in a good conductive state. That is, the conductivity of the circuit depends on the moisture-sensitive element. When the humidity gradually increases, the distance between the carbon particles increases, so that the resistance value of each moisture-sensitive element increases, and becomes infinite when the humidity is equal to or higher than the specified humidity. At this time, conduction depends on the resistor.

FIG. 2 shows a change in a combined resistance value with respect to a change in humidity of each unit composed of each humidity sensing element and a resistor connected in parallel with the humidity sensing element. That is, the curves A, B, C, D, E, and F correspond to the terminals 17, 18, 19, 2 in FIG.
9 shows resistance value changes at 0, 21 and 22.
The resistance value of each of these combination units rapidly rises above a specific humidity, but does not rise above a specified resistance value because resistors having a specific resistance value are connected in parallel. Then, since these six combination units are connected in series, the change in the total combined resistance value is as shown in FIG. 3, and the change in the output voltage of the terminal 4 is as shown in FIG. As is clear from FIGS. 3 and 4, both the resistance value and the output voltage change gently with the change in humidity, and have appropriate sensitivity to humidity in any humidity range, enabling detection of a wide range of humidity. Indicates that

[0019]

As described above, according to the present invention,
Slow down the combined resistance change and output voltage change,
Since appropriate sensitivity can be provided in the entire humidity range of 20% RH or more, highly accurate humidity detection can be performed over a wide humidity range. In addition, by using a moisture-sensitive element in which conductive powder is dispersed in a water-absorbing polymer, direct current can be applied, and the effect of significantly reducing costs can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a change in resistance value with respect to a change in humidity of each unit in which each moisture-sensitive element and a resistor are connected in parallel in the embodiment.

FIG. 3 is a diagram showing a change in resistance value with respect to a change in humidity when six combination units are connected in series.

FIG. 4 is an output voltage characteristic diagram in the embodiment.

FIG. 5 is a configuration diagram of a conventional example.

FIG. 6 is an output voltage characteristic diagram of the conventional example.

[Explanation of symbols]

3, 11-16: resistor, 5-10: moisture sensitive element, 4: output terminal.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takehiko Yoneda 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-4-132947 (JP, A) JP-A-51- 16978 (JP, A) JP-A-57-26775 (JP, A) JP-A-57-17882 (JP, A) JP-A-4-364456 (JP, A) JP-A-57-211051 (JP, A) JP-A-59-5819 (JP, A) JP-A-56-135155 (JP, U) JP-A-56-68153 (JP, U) JP-A-58-62257 (JP, U) (58) (Int.Cl. ⁷ , DB name) G01N 27/12 G01N 27/04 WPI (DIALOG)

Claims (2)

(57) [Claims] 1. A plurality of moisture-sensitive elements having different resistance value changes with respect to humidity change are connected in series, and a resistor having a unique resistance value is connected in parallel to each of the humidity-sensitive elements. A humidity signal corresponding to the combined resistance value of the above. 2. The humidity detecting device according to claim 1, wherein the moisture-sensitive element is made of a water-absorbing polymer having conductive powder dispersed therein.