JPS58134403A - Moisture sensitive element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a humidity sensing element that detects humidity as a change in electrical resistance and is used to control humidity in air conditioners, humidifiers, microwave ovens, warehouses, printing machines, etc. .

Most conventional moisture-sensitive elements have used electrolyte materials, and others have used organic polymer materials.

As an electrolyte material, there is, for example, a so-called Dammer-type electrolyte made of L↓C1, but this has the following drawbacks.

■ In high humidity areas, it absorbs moisture and deliquesces.

■ Since it sublimates over a long period of time, it is necessary to calibrate it at regular intervals.

@, If the composition ratio of LA and CJ is only one type, the measurement range is narrow, so it is necessary to combine several types with different ratios, but as the number of elements increases, the number of measurement terminals increases accordingly. This makes assembly (and control circuitry) troublesome.

etc.

Further, as a material using the organic polymer material, for example, nylon is used as an alternative to conventional hair, and the change in length when it swells due to moisture is detected. This also had the following drawbacks.

■ The upper limit of the operating temperature is at most 60'C, and the range of use is limited to the contact wheels.

■ Accuracy is low due to large hysteresis during expansion and contraction.

■ Extremely slow response to changes in humidity.

etc.

The present applicant has already proposed various new moisture-sensitive elements that eliminate the above-mentioned conventional drawbacks, and among them, Zr0
The most favorable results were obtained with a device containing a mixture of MgO and MgO. Specifically, Zr01 and M with an average particle size of 1 μm or less
A porous sintered body is formed by mixing fine powder of gO in a prescribed ratio, pressurizing this at a prescribed pressure, and heating it at a prescribed temperature for a prescribed time, and electrodes are inserted into this sintered body. It is something.

By constructing the porous sintered body in this way, the electrical resistance is determined by the moisture impregnated and adsorbed in the voids of the sintered body between the electrodes.
In other words, it is possible to properly respond to humidity.

However, it has been found that the moisture-sensitive element formed by mixing ZrOi and ZrO has some problems such as smearing.

■ The resistance value tends to increase gradually over a long period of time.

■The humidity measurement range is narrow because the rate of change in resistance value is too steep.

etc.

The present invention was made in order to solve such a problem of melting point, and uses a moisture sensing element formed by mixing ZrO2 and igO as a matrix, and uses this matrix as a matrix of P, O, .24WO, .flH.
! It is treated with an aqueous solution of 0.

The present invention will be explained in detail below.

First, the order of preparing the samples is as shown below.

■ Z with a purity of 99.99% or more and an average particle size of 1 μm or less
Prepare r01 and MgO powder. And ZrO,
Weigh out 1 mol % of t99 mol % Mgo, put these two types of fine powder into ethanol in a plastic container, add menopol at the same time, and wet mix in a ball mill.

■ After wet mixing, leave to remove supernatant liquid and heat dry.

■ Knead the dried powder with an aqueous solution of polyvinyl alcohol.

(2) The kneaded product is put into a mold and a predetermined pressure (for example, 300ky/am" or 50oky/male) is applied for 3 to 5 minutes at room temperature to form tablets.

■ Place the tablet in an electric furnace and heat it to a specified temperature (e.g. 900℃)
Heat for 2 hours, then cool naturally after heating. In this way, a porous sintered body is formed.

(2) This sintered body is sliced into a predetermined thickness (approximately 300 μm) using a diamond blade, and cut into rectangular shapes with each side having a predetermined length (approximately 4 to 5 yen). Then, Figure 1(a)
(b) A porous sintered body (1) made of a mixture of Zr01 and MgO as shown in (=) is formed, and this becomes the base material of the present invention.

■ On the front and back sides of this matrix (1), print a luteinium-based thick film paste to the extent that the outer periphery of the matrix (1) remains slightly to form at least one pair of electrodes (2) and (3). Electrode (2
) (3), an electrode wire (4) made of platinum iridium (
5) are bonded using a ruthenium-based thick film paste.

■ Bake this in a conveyor furnace of maximum soo ”C.

Next, the element thus formed is subjected to a proton conductor solution immersion treatment. A proton conductor is a proton conductor (
H) becomes a carrier and conducts electricity, and H”1 inside the crystal
This method utilizes the characteristic that 1 degree changes depending on the moisture concentration of the external surrounding air, that is, the equilibrium relationship with humidity, and that the electric conductivity also changes. Specifically, the material used is phosphotungstic acid (PtOs"24W03.fil(,o)). This immersion treatment method will be explained in detail below.

■ P2O5・24WO1・nHlo in deionized water
Specifically, 400 ml of PT (hereinafter referred to as PTA) was weighed and added to 10 cc of deionized water to a predetermined concentration, and stirred to prepare a 4.0% by weight aqueous solution.

(2) Pour this aqueous solution adjusted to a predetermined concentration into a beaker 6, immerse the element formed in FIG. 1 in it, and apply ultrasonic waves for 20 to 30 minutes.

(2) Take out the element from the beaker and remove moisture by heating or self-thermal drying to obtain a moisture-sensitive element (6) according to the present invention.

The results of an experiment to determine whether the moisture sensing element (6) subjected to the PT ice water solution immersion treatment as described above has the desired characteristics will be explained.

First, the moisture sensing element (6) is mounted on the support device (
7). That is, the terminal (8) for connecting the electrode wires (4) (5) of the moisture sensitive element (6)
9) and the ground terminal αυ are planted on the insulating substrate (11). In order to eliminate the negative influence on the resistance value of the moisture sensitive element (6) due to the impedance between the terminals (8) and (9),
) A guard ring a◆ with a constant gap is provided on the outer periphery of (9), and this guard ring I is connected to the ground terminal α〃.

As shown in FIG. 3, the moisture-sensitive element to be measured (6) configured in this way is connected in series with a resistor αe (for example, IOKΩ) to a signal source α9 of about 100 Hz, and further connected to this signal source α9. A voltage iaη is connected in parallel with the resistor ae.

Next, the measurement results will be explained based on the characteristic diagrams shown in FIG. 4 and below.

■ Figure 4 shows the R-
In the H characteristics, characteristics (a), (b), (c), and (e) are characteristic diagrams immediately after sample preparation, 8 days later, 20 days later, 35 days later, and ss days later, respectively. From this characteristic diagram, at least 10~
It can be seen that there is almost no change over time within the range of 90% RH. In addition, the initial characteristic U) is the resistance when the relative humidity is increased from 30-50-70 → 90%RH and then decreased from 90-70-50-30-10%RH as shown by the arrow. Although there is a slight hysteresis, there is no problem in practical use, and the measurement atmosphere temperature is 25℃.
And so.

■ Figure 5 shows the change over time at the same relative humidity of a humidity sensing element subjected to PTAT processing.The horizontal axis shows the number of days that have passed, and the vertical axis shows the relative humidity after n days (Xn) and the relative humidity immediately after sample preparation. (Xo) (ΔRH=Xn - Xo)
Characteristics (f) are for the device treated with PT, and characteristics (g) are for the device not subjected to PT, both of which were left at an indoor humidity of about 54'%. As can be seen from these characteristics, the characteristics (g) of the element without PTAT process gradually change more with the passage of time, and tend to increase even after 50 days have elapsed. On the other hand? ? The characteristics of the element that has been modified are approximately -10% after 3s days have passed.
shows a constant value.

■ Figure 6 shows the heating refresh effect of a moisture sensing element with a P-tem ring. In the figure, characteristic (A) is a copy of the initial characteristic (A) in FIG. 4. Further, the characteristics (ch)(su) are those obtained by refreshing the sample preparation machine after a predetermined period of time has elapsed and checking the changes in the characteristics at that time. Specifically, under conditions of normal temperature and humidity, the characteristic temperature is refreshed after 55 days, that is, 1 at 400℃.
It was heated for 5 seconds, then left for S minutes to equilibrate with the external surrounding air, and then the resistance value was measured at each relative humidity. Characteristic(
2) shows the results of measurement after refreshing the device again after 2 days. These characteristics (a) (su) (g)
It can be seen that the Karari Fresh operation is effective.

(2) It has been confirmed through various experiments that the temperature dependence of the moisture-sensing characteristics of the PTAT element is 0.7% RH/''C, which is considerably better than known moisture-sensing elements.

As described above, in the present invention, a mixed sintered body of ZrOg and MgO is used as a base body, and this is treated with a PTMU water solution to produce a moisture-sensitive element. As is clear from the characteristic diagrams of FIGS. 4, 5, and 6, it has various characteristics such as:

■ There is little change over time, that is, the characteristics become extremely stable after about 35 days.

■ The overall resistance value varies from high relative humidity to low relative humidity.
and the measurement range becomes very wide, at least 10 to eo%m.

■ Hysteresis is even smaller than before PT human processing.

■ Heating refresh operation is valid.

[Brief explanation of the drawing]

Figure 1(a) is a front view of the base element, Figure 1(b)
is a side view of the same, FIG. 2 is a perspective view showing the moisture sensing element according to the present invention mounted on a support device, FIG. 3 is a circuit diagram for measuring characteristics, and FIG. 4 shows changes over time in PTA treatment theory. Show R-H
FIG. 5 is a characteristic diagram comparing changes over time before and after p'rm treatment, and FIG. 6 is a characteristic diagram showing the fresh effect of heating. (1) Porous sintered body, (2) (3) Electrode, (4) (5) Electrode wire, (6) Moisture sensing element, (7)・Support device, (8) (9)...terminal,
Ql...Insulating base, α-to... Earth terminal, α-fathom...
・Guard ring, cod...signal source, ae...resistance, r
iη...Voltage needle. Patent Applicant Co., Ltd. (Neral Attorney Toshio Furusawa, also Kano-male. Figure 1 Figure 2 Figure 5 ) September 1, 1980, 1932, 轡 1, No. 17880, 2, Title of the invention: Temperature sensing element 3 Relationship with the person making the amendment case: 41m! [11 people 4, page 2 of the attorney's specification In the 13th to 17th line, “■ L
``It will be troublesome for L and Cj...'' is written as [■
If the concentration of the LICj solution as an electrolyte is only one type, the range of relative humidity that can be measured is extremely narrow. So 1. In order to accurately measure humidity over a wide range, elements made with different solution concentrations for each measurement range have been combined. However, as the number of elements to be combined increases, the number of measurement terminals increases accordingly, and a switch circuit is also required to control this combination, and the structure is complicated or large, making assembly difficult. To become. ” he corrected.

Claims (1)

[Claims] (1) Fine powders of ZrO* and MgO are mixed in a predetermined ratio and treated at a predetermined pressure, time, and temperature to form a porous sintered body, and this sintered body has at least A matrix is provided with a pair of electrodes, and P, 0. @24WO. - A moisture-sensitive element characterized by being made of a proton conductor treated with an aqueous solution of nJo. (2. A moisture sensing element as described in claim 1, in which the mixing ratio of ZrO2 and MgO is 99:1. (3) In claim 1 or 2, P, 0.・24WO,・Otori H,O water droplet concentration is about 4
．． Moisture sensitive element with 0% by weight. (4) A moisture-sensitive element according to claim 1, wherein the particle size of the fine powder of Zr01 and MgO is 1 μm or less on average.