JPS59116536A - Humidity sensor - Google Patents

Abstract

PURPOSE:To stabilize temporal change and humidity response and to improve reliability in humidity characteristics, by controlling the average diameter of pores and the porosity of an electrode material and a raw ceramic body used in a porous ceramic humidity sensor. CONSTITUTION:A P type semiconductor metal oxide raw ceramic body has a porosity in the range of 20-40% and average pore diameter in the range of 0.01-1mum. In this ceramic body, a ruthenium oxide porous electrode, which has an average pore diameter in the range of 0.01-1mum, is provided. A humidity sensor having this constitution is formed, e.g., by the following procedure: by using MgCr2O4-TiO2 series P type semiconductor ceramic humidity sensor material, compounding, mixing, temporary burning, and grinding are sequentially performed according to an ordinary ceramic industry method; a binder is added and granulation is performed; granulated powder is formed into a plate shape and burned and the raw ceramic body is formed; an electrode paste, which includes ruthenium oxide powder having the granule diameter of about 0.01-1mum and glass frit, is applied on both sides of the raw ceramic body by screen printing and burned; and the ruthenium oxide electrode is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a humidity sensor used in food cooking equipment such as microwave ovens, air conditioning equipment such as air conditioners, humidity control systems, and the like.

Conventional configurations and their problems Conventionally used electric moisture sensing elements include those that use electrolyte materials such as lithium chloride (LiC1), and those that have an oxide film formed on the surface of a single crystal.

Those with carbon dispersed in hydrophilic organic polymers, those with surface oxidized metals, and those using/with colloidal membranes.

Alternatively, there is an element using a metal oxide porous material.

All of these methods detect changes in humidity as changes in the amount of electricity, but each has major problems.

For example, electrolyte water dissolves into water under condensation,
It is unstable and has reliability problems.

-! j, da, those using single crystal are expensive,
Not resistant to dirt. Those using organic polymers have poor responsiveness, and those using vapor-deposited films have poor compatibility, require a long time to stabilize the film, and have unstable characteristics.

A1203, Cr2 o3 in metal oxide porous body
, or those using Ni2O3 have virtually no drawbacks as described above, but on the other hand, they generally have high resistance,
Not only are they difficult to use in practice, but they also have the problem of being susceptible to dirt, and a common problem with each of them is deterioration of characteristics due to dirt. To solve these problems, metal oxide porous ceramics are heated from the outside or from the surface to remove dirt.

However, under very harsh conditions, some
7 shows changes. If you reduce the average pore diameter of the electrode, the porosity of the ceramic element, and the average pore diameter, it will be fatal (
d is getting better, but a problem arises in that the response becomes slow.

``One aspect of the invention'' The present invention solves the above-mentioned problems and provides a humidity sensor that has good responsiveness, little change over time, and has a long life.

Structure of the Invention The present invention prevents inorganic and organic substances harmful to humidity characteristics from penetrating into the ceramic body by controlling the average pore diameter and porosity of the electrode material and ceramic body of a porous ceramic humidity sensor. The above purpose has been achieved by preventing this.

That is, in the present invention, by providing small-diameter pores on the surface of the ruthenium oxide electrode, deterioration of characteristics due to contamination is reduced, and by providing the electrode on the ceramic body, the life characteristics are further improved. By reducing the brane size of the element body, the grain boundary area increases,
This makes it possible to lower the sensor resistance value and makes the circuit easier to use.

Description of Examples Using MgCr204-TlO2-based P-type semiconductor ceramic humidity sensor +A barbs, blending, mixing, calcination, and pulverization were performed in sequence according to the usual ceramic method, and then a binder was added and granulated. . 750 kg/c of this granulated powder
4 tD positive pressure 4 mM x 47/IJff x 0
．． Form it into a plate shape with a size of 25 mm and heat it in air for 110 minutes.
The ceramic body was fired for 2 hours at a temperature ranging from 00C to 13000C. An electrode paste containing ruthenium oxide powder with a particle size of about 0.01 μm to 1 μm and glass frit is applied to both sides of this ceramic body to a thickness of 10 to 3 Q μm by screen printing, and the temperature ranges from 750°C to 900°C. A ruthenium oxide electrode was formed by baking at a temperature of

The porosity, average pore diameter, and rate of change over time of these ceramic bodies and ruthenium oxide electrodes are shown in Tables 1 and 2, respectively. Furthermore, Table 3 shows the synergistic effect of the ceramic body and the ruthenium oxide electrode in terms of average pore diameter and rate of change over time. In addition, the humidity response is the same as when changing the relative humidity from 10% to 50% at a temperature of 20°C.
The time taken to reach the normal fMi when changed to 0% is shown.

Ushi, note 11 test is 10 to 54000 element temperature
This was carried out by adding a temperature cycle (cleaning cycle) in which the temperature was maintained for 1 second to incinerate the contaminants, and the temperature was then maintained at room temperature for the next 10 seconds, and the rate of change in element resistance due to this was defined as the rate of change in life.

(Leaving space below) Table 1: Ceramic body Table 2 Ruthenium dioxide electrode Table 3: Synergistic effect between ceramic body and ruthenium oxide electrode As is clear from the results in the above table, The average pore diameter is within the range of 0.01 to 1 μm, and the porosity of the ceramic body is 20 to 40%.
Humidity sensors within this range have good humidity responsiveness and change over time.

Effects of the Invention As is clear from the above explanation, the humidity sensor of the present invention (
In an atmosphere with harsh humidity resistance characteristics, changes over time,
Since the humidity response is stable, the humidity characteristics are highly reliable and can be easily used in devices such as humidity measuring devices and humidity meters.

Claims (1)

[Claims] P-type semi-core gold with a porosity in the range of 20% to 40% and an average pore diameter in the range of 0.01 μm to 1 μm (similar oxide ceramic body with an average pore diameter of 0.01 μm)
A humidity sensor comprising a porous electrode made of ruthenium oxide having a diameter ranging from μ7n to 1 μm.