JPH04118547A - Humidity sensor - Google Patents

Abstract

PURPOSE:To enable humidity to be detected with high accuracy at all times by detecting the humidity in the condition where the periphery of a humidity detection means is heated up to or above the predetermined temperature level. CONSTITUTION:Output signals from a humidity sensor 4, the first temperature sensor 3 and the second temperature sensor 5 are respectively measured to preliminarily obtain a saturated vapor amount curve at each temperature level. A vapor amount on the heater 2 where the first temperature sensor 8 and the humidity sensor 4 are laid, is then obtained. Thereafter, the internal temperature of a refrigerator, or a ratio of the aforesaid vapor amount to a saturated vapor amount for the second temperature sensor 5 is obtained, thereby obtaining humidity. According to the aforesaid construction, humidity under a freezing point can be obtained with ease and high accuracy. Also, measurement can be immediately taken continuously, even when a door is opened and closed, because there is no dew condensation.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a humidity sensor, and particularly to a humidity sensor that prevents the influence of dew condensation.
The present invention relates to a humidity sensor that performs highly accurate temperature detection.

(Conventional technology) In recent years, the environment has become so-called 15 to 15 o'clock in temperature and high humidity.

80-100% food preservation technology is attracting attention.

Temperature and humidity play a major role in the food storage environment, so it is necessary to detect the temperature and humidity with high precision and control according to the detected values.
To detect humidity in ice temperature storage, a humidity sensor is used that detects changes in electrical resistance or capacitance due to adsorption of water molecules to a temperature-sensitive film made of a polymer film, ceramic, or the like.

However, when such a sensor is used in an icy temperature environment, dew condenses when outside air is introduced when the storage door is opened and closed, making it impossible to measure humidity for several tens of minutes thereafter. Furthermore, there is a problem in that the characteristics of the sensor deteriorate due to repetition of such a dew condensation cycle. For this reason, the ice temperature storage warehouse was not equipped with a temperature sensor, making it impossible to detect the humidity inside the warehouse.

(Problems to be Solved by the Invention) As described above, when a conventional humidity sensor is used in an icy temperature and high humidity environment, accurate humidity detection cannot be performed due to dew condensation. There was a problem in that it was necessary to wait until the condensation caused by introducing outside air by opening and closing the door disappeared.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a humidity sensor that can continuously detect humidity with high accuracy in an environment of freezing temperature and high humidity without being affected by dew condensation. .

[Structure of the invention]

(Means for Solving the Problems) Therefore, in the present invention, a heating means is provided that locally heats only the area around the humidity detection means, and the humidity of the environment to be measured is detected while being heated to a predetermined temperature or higher. The ambient temperature and the environmental temperature of this humidity detection means are measured, and the humidity is detected from these values and the detected humidity.

(Function) According to the above configuration, since humidity detection is performed with only the area around the humidity detection means locally heated to a predetermined temperature or higher, even if outside air enters, condensation is immediately prevented. It becomes possible to maintain the humidity at M1 even when there is no humidity.

Furthermore, since the humidity is measured without condensation, deterioration of the sensor itself can be prevented.

Further, it is possible to constantly perform M1 constant humidity.

It is desirable that the heating temperature of this heating means be set to a temperature that does not cause dew condensation even when exposed to outside air. For example, in the case of a food storage, a heating means that heats the food to about room temperature may be used.

(Example) Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1(a) and FIG. 1(b) are diagrams showing a humidity sensor according to a first embodiment of the present invention.

This humidity sensor is installed to detect the humidity in an ice temperature storage, and is equipped with a substrate 1 made of quartz that is highly thermally insulating and has a thickness of 1 mm and 10 Ilffi on each side. A heater 2 made of a titanium nitride (TiN) thin film with a film thickness of 1 μm, a first temperature sensor 3 and a humidity sensor 4 arranged in parallel on the upper layer, and a heater 2 arranged on a quartz substrate 1 with a slight distance from these sensors. and a second temperature sensor 5 provided therein.

This humidity sensor 4 is made of titanium nitride (TiN)! Aluminum nitride (Aj
! N) 6, it is composed of a comb-shaped electrode 41 made of a thin chromium film, and a moisture-sensitive film 42 made of a polyimide film formed to cover the upper layer of the comb-shaped electrode 41. The capacitance change is taken out from the electrode 41.

The first temperature sensor 3 also includes an electrode 31 made of an aluminum thin film placed on the heater 2 made of a titanium nitride (TiN) thin film via an aluminum nitride (Aj!N) 6 as an insulating film, and an electrode 31 made of an aluminum thin film. Both ends or connected platinum (
Meandering resistance pattern 32 consisting of a Pt) pattern
The temperature is detected from the change in resistance value based on the temperature change.

Furthermore, the second temperature sensor 5 includes an electrode 51 made of an aluminum thin film formed directly on the substrate 1, and a meandering resistance pattern 52 made of a platinum (pH pattern) connected at both ends to the electrode 51 formed directly on the substrate 1. As with the first temperature sensor 3, the temperature is detected from a change in resistance value based on a temperature change.

Next, measurement of humidity using this humidity sensor will be explained.

The outputs of the humidity sensor 4, the first temperature sensor 3, and the second temperature sensor 5 are each determined as Mj.

Each of these measured values is a(%R,H,).

b (℃) (about room temperature), c ("C)".

First, as shown in FIG. 2, a saturated water vapor amount curve at each temperature is determined. Here, the vertical axis is the saturated water vapor amount (
g/1l13), and the horizontal axis is temperature ("C). Temperature S,
Letting the saturated water vapor amount at time c be B and C, respectively, the water vapor amount X (g/m') on the heater 2 where the first temperature sensor and humidity sensor are placed is calculated using the following formula (1). It will be done.

χ (g/m3) = aXB... (
1) Thereafter, the humidity y (%R, H,) can be determined by determining the ratio of the internal temperature, that is, the output C of the second temperature sensor, to the saturated water vapor amount C.

y (%R,H,)-x/CX100-axB/CX100-- (2) In this way, the humidity at freezing temperature can be determined extremely easily and with high precision.

Furthermore, since there is no condensation, measurements can be carried out immediately and continuously even when the door is opened or closed, and deterioration of the sensor can be prevented.

In addition, when using a conventional humidity sensor that does not have a heater, the condensation does not disappear until about 50 minutes have passed after the door is opened and closed, making it impossible to accurately measure humidity due to the increase in humidity due to condensation. Furthermore, according to the present invention, humidity can be detected with high accuracy even immediately after opening and closing the door, and high-precision detection can be performed at all times.

Furthermore, according to the above configuration, since everything can be formed using thin film technology, it is possible to significantly reduce the size. Moreover, if peripheral circuits such as arithmetic circuits, which are not shown in the above embodiments, are also integrated, further miniaturization can be achieved.

As the humidity sensor, a capacitance change type sensor or a resistance change type sensor may be used, and when used in a high temperature region, AJzOi ceramics may be used. Furthermore, the material of the moisture-sensitive resistive film or the material of the insulating thin film can be changed as appropriate.

Furthermore, in the above embodiment, all sensors are formed of thin films,
It may be formed into a monolink, or it may be appropriately formed into a chip and formed into a hybrid.

Embodiment 2 Next, as a second embodiment of the present invention, an example in which each sensor is formed into a chip shape will be described.

As shown in FIG. 3, this humidity sensor has a thermally insulating thickness of 1. mm length and width each 1011I+! A substrate 11 made of quartz, a heater 12 disposed thereon, a first temperature sensor 13 and a humidity sensor 14 arranged in parallel on the upper layer, and a quartz substrate 11 placed a little apart from these sensors.
and a second temperature sensor 15 disposed above.

Each of these sensors is in the form of a chip, and each is fixed using an adhesive with good thermal conductivity.

〔Effect of the invention〕

As explained above, according to the present invention, humidity is detected while the area around the humidity detection means is heated to a predetermined temperature or higher, so that humidity can always be measured without condensation. , it is possible to always detect humidity with high precision.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a humidity sensor according to a first embodiment of the present invention;
FIG. 2 is a diagram showing a saturated water vapor amount curve used for measurement with the same humidity sensor, and FIG. 3 is a diagram showing a humidity sensor according to a second embodiment of the present invention. 1. Board, 2. Heater, 3.. First temperature sensor,
4. Humidity sensor, 5.. Second temperature sensor, 6.. Insulating film, 11.. Substrate, 12.. Heater, 13.. First
Temperature sensor, 14. Humidity sensor, 15.. Second temperature sensor, 31.. Electrode, 32.. Resistance pattern, 4
1. Electrode, 42.. Moisture sensitive membrane, 51.. Electrode, 52.
・Resistance pattern. Figure 2 Figure 2

Claims (1)

[Scope of Claims] Humidity detection means installed in a part of the environment to be measured and detects humidity; heating means for locally heating the area around the humidity detection means to a predetermined temperature or higher; and the humidity detection means a first temperature detection means for detecting the ambient temperature of the environment; and a second temperature detection means for detecting the temperature of the environment in which the humidity is to be measured; A humidity sensor characterized in that the humidity of the environment to be measured is obtained by converting based on the output of the means and the output of the second temperature detecting means.