JPH08193966A - Humidity sensor - Google Patents

Abstract

PURPOSE: To provide a humidity sensor with reduced electric power and capable of detecting humidity in real time. CONSTITUTION: A humidity sensor is provided with a first thermally sensitive resistor 1 for generating heat by itself with Joule heat being arranged in measurement atmosphere and a second thermally sensitive resistor sealed into a dry atmosphere. Humidity is measured by utilizing the phenomena that the thermal dissipation of the first and second thermally sensitive resistors changes with humidity, and measuring the voltage drop of the first and second thermally sensitive resistors. The humidity sensor is provided with a crosslinking structure 6 consisting of an electrically insulated thin film which is crosslinked on a recessed part of a substrate 5 with a recessed part, a first thermally sensitive resistor 1 fixed inside or on the crosslinking structure 6, and a support leg member 7 for supporting the crosslinking structure 6. The whole shape of the crosslinking structure 6 and the support leg member 7 is of H-shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidity sensor for detecting the amount of water vapor in an atmosphere such as an air conditioner, a dehumidifier, a cooker or a cultivation house.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for detection control of humidity (either relative humidity or absolute humidity is acceptable) in air conditioners, dehumidifiers, humidifiers, cookers, cultivation houses and the like. In order to meet this demand, various types of humidity sensors have been proposed.

The conventional method is an electric resistance type or electrostatic capacity type which applies a change in electric characteristics due to moisture absorption of a moisture sensitive material, or a heat conduction type which detects a change in heat conduction of air due to the presence or absence of water vapor in the air. However, the heat conduction type has excellent long-term stability because it does not absorb water.

The conventional heat conduction type humidity sensor measures the humidity by utilizing the fact that the thermal diffusion of the temperature sensitive resistor changes depending on the humidity. As shown in FIG. 6, this humidity sensor is provided with two temperature sensitive resistors 41 and 42, one of which is exposed to the measurement atmosphere (outside air), and the other. The temperature sensitive resistor 42 is enclosed in a dry atmosphere. Humidity is detected by measuring the output value of an electronic circuit (for example, Wheatstone bridge circuit) that outputs an output voltage related to the voltage drop of these two temperature sensitive resistors 41 and 42.

When manufacturing a conventional humidity sensor, as shown in FIGS. 6 and 7, first, the temperature sensitive resistors 41 and 4 are used.
The two are fixed to the different stems 45 via the holding bases by bonding with an adhesive (inorganic or organic adhesive is selectively used depending on the operating temperature), welding, or the like, and then terminal connection is performed by wire bonding. The stem 45 to which the temperature sensitive resistor 41 is fixed is covered with a cap 46 having a vent hole by welding.

On the other hand, the temperature sensitive resistor 42 has a low temperature (-40
It is sealed in dry air by covering the stem 45 with a cap 47 by welding at (° C.). Then cap 4
6, 47 are press-fitted into the cap fixing plate 48, a metal case 49 is placed on the outside of the cap fixing plate 48, and then a metal cover 50 is attached to complete the process.

[0007]

However, in the conventional humidity sensor, there is a limit to miniaturization of the temperature sensitive resistor, and therefore, in order to raise the temperature of the temperature sensitive resistor to a predetermined temperature, about 400 mW is required. It needs electricity. In the conventional humidity sensor, the time constant of the temperature sensitive resistor is set to 10
Since it can only be done in about a second, it becomes impossible to detect humidity in real time if a drive system is adopted that lowers the temperature of the temperature sensitive resistor for a certain period during humidity detection in order to reduce power consumption. .

An object of the present invention is to provide a humidity sensor that can achieve low power consumption and can detect humidity in real time.

[0009]

In order to solve the above-mentioned problems, the present invention provides a first temperature-sensitive resistor which is placed in a measurement atmosphere and self-heats by Joule heat, and a first temperature-sensitive resistor which is enclosed in a dry atmosphere. 2 temperature-sensitive resistors, and the first and second
In the humidity sensor for measuring the humidity by utilizing the fact that the heat dissipation of the temperature-sensitive resistor changes depending on the humidity and measuring the voltage drop of the first and second temperature-sensitive resistors, A crosslinked structure made of an electrically insulating thin film crosslinked on the recess of the substrate, the first temperature-sensitive resistor fixed inside or on the crosslinked structure, and a supporting leg for supporting the crosslinked structure. It has a member, and the said bridge | crosslinking structure and the said support leg member are H-shaped in the whole shape, It is characterized by the above-mentioned.

Further, according to the present invention, there is provided a first temperature-sensitive resistor arranged in a measurement atmosphere, a heating element which self-heats by Joule heat to heat the first temperature-sensitive resistor, and a dry atmosphere. And a second temperature-sensitive resistor enclosed in the second temperature-sensitive resistor, wherein the heat dissipation of the first and second temperature-sensitive resistors is changed by humidity, and the first and second temperature-sensitive resistors are used. In a humidity sensor that measures humidity by measuring the voltage drop of a temperature resistor, a crosslinked structure made of an electrically insulating thin film crosslinked on the concave portion of a substrate having a concave portion, and inside or on the crosslinked structure body. The fixed first temperature-sensitive resistor, the heating element fixed inside or on the cross-linked structure near the first temperature-sensitive resistor, and a supporting leg that supports the cross-linked structure. A member, and the bridge structure and the support leg member are Shape and wherein the forming the H-shaped.

[0011]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention. As shown in FIG. 1, the humidity sensor of the present invention is
Of the temperature sensing resistor 1 (resistance value R1) and the second temperature sensing resistor 2 (resistance value R2), and the two fixed resistors R3 and R4 constitute a Wheatsbridge circuit. The humidity is measured by utilizing the fact that the thermal diffusion of the temperature resistor 1 changes depending on the humidity. The power supply device 3 is connected to the input terminal of the Wheatsbridge circuit.

The first temperature-sensitive resistor 1 is arranged in a measurement atmosphere, and is supplied with an electric current by the power supply device 3 at the time of measurement to self-heat by Joule heat to reach a predetermined temperature. It is something to measure. The second temperature sensitive resistor 2 is enclosed in a dry atmosphere. This humidity sensor utilizes that the heat dissipation of the first and second temperature sensitive resistors 1 and 2 changes depending on the humidity, and
And the humidity is measured by measuring the voltage drop across the second temperature sensitive resistors 1 and 2. That is, with reference to the resistance value R2 of the second temperature sensitive resistor 2, the output voltage Vo of the Wheats bridge circuit corresponding to the change of the resistance value R1 of the first temperature sensitive resistor 1 at a predetermined temperature is Humidity is detected by the change.

As shown in FIG. 2, a substrate 5 having a recess 4 is formed.
A bridge structure 6 made of an electrically insulating thin film is bridged on the recess 4. The first temperature-sensitive resistor 1 is fixed inside or on the cross-linked structure 6. The bridge structure 6 is supported by a support leg member 7 provided on the substrate 5. The bridging structure 6 and the supporting leg member 7 are H-shaped as a whole.

Next, a method of manufacturing a main part of the humidity sensor of the present invention will be described.

A SiO ₂ film 8 having a thickness of 3 μm is formed on a substrate 5 made of silicon by, for example, a sputtering method.

A thin film platinum pattern of the temperature sensitive resistor 1 or 2 is formed on the SiO ₂ film 8 by the photolithography technique.

SiO ₂ film 8 around the temperature sensitive resistors 1 and ₂
Are removed by etching using a photolithography technique, and the temperature sensitive resistors 1 and 2 are formed so as to be located on the bridge structure 6 of the SiO ₂ film 8. At this time, the bridging structure 6 and the supporting leg member 7 supporting the bridging structure 6 are formed so that the entire shape is H-shaped. If formed in this way, the escape of heat from the cross-linked structure 6 can be minimized and the thermal efficiency can be increased. Further, if the corners of the SiO ₂ film 8 after etching are formed in a curved shape, the strength is increased.

Two sensor chips obtained by cutting with a dicing saw or the like are fixed to different stems 9 by adhesives (inorganic or organic adhesives are selected depending on the operating temperature), or by welding, etc. Connect terminals by wire bonding.

The stem 9 to which the temperature sensitive resistor as the first temperature sensitive resistor 1 is fixed is covered with a cap 10 having a vent hole by welding.

On the other hand, the temperature-sensitive resistor to be the second temperature-sensitive resistor 2 is enclosed in dry air by covering the stem 9 with the cap 11 by welding at a low temperature (-40 ° C).

After that, the caps 10 and 11 are press-fitted into the cap fixing plate 12, the metal case 13 is put on the outside of the cap fixing plate 12, and then the metal cover 14 is attached.

The first and second temperature sensitive resistors 1 and 2
Can be constructed in a very small size, the electric power for raising the temperature of the temperature sensitive resistors 1 and 2 to a predetermined temperature is several tens mW.
The time constant can be set to several ms. Therefore, the first and second temperature-sensitive resistors 1 and 2 can detect humidity only for a time period of about several tens of ms per second,
Substantially lower power consumption of several mW can be achieved, and battery drive is possible.

Next, a second embodiment of the present invention will be described.

In the second embodiment, as shown in FIG.
A first temperature-sensitive resistor 1 arranged in a measurement atmosphere, a heating element 15 that self-heats by Joule heat to heat the first temperature-sensitive resistor 1, and a second temperature-sensitive resistor enclosed in a dry atmosphere. The temperature sensitive resistor 2 of FIG.

The heating element 15 is made of SiO _{2 of the} substrate 5.
It is formed on the film 8. The heating element 15 and Si
A SiO ₂ film 16 is further formed on the O ₂ film 8. The first temperature sensitive resistor 1 is formed on the SiO ₂ film 16.
Is stuck. As described above, the heating element 15 is arranged in the vicinity of the first temperature-sensitive resistor 1, and is supplied with an electric current at the time of measurement and self-heats due to Joule heat to generate the first temperature-sensitive resistor 1. It is heated to a predetermined temperature. The second embodiment is the same as the first embodiment except for these configurations.

The present invention is not limited to the Wheatstone bridge, but can be applied to an electronic circuit capable of measuring the voltage drop of the first and second temperature sensitive resistors 1 and 2.

[0028]

According to the present invention, it is possible to reduce the power consumption and to detect the humidity in real time.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a perspective view showing a main part of the first embodiment of FIG.

FIG. 3 is a perspective view showing a main part of the first embodiment of FIG.

FIG. 4 is an exploded perspective view showing a main part of the first embodiment of FIG.

FIG. 5 is a perspective view showing a main part of a second embodiment of the present invention.

FIG. 6 is an exploded perspective view showing a conventional humidity sensor.

7 is a perspective view showing a main part of the humidity sensor of FIG.

[Explanation of symbols]

1 1st temperature-sensitive resistor 2 2nd temperature-sensitive resistor 3 Power supply device 4 Recessed part 5 Substrate 6 Bridge structure 7 Support leg member 8 SiO ₂ 9 Stem 10, 11 Cap 12 Cap fixing plate 13 Metal case 14 Metal Cover 15 heating element

Claims (2)

[Claims] 1. A first temperature-sensitive resistor which is arranged in a measurement atmosphere and self-heats by Joule heat, and a second temperature-sensitive resistor which is enclosed in a dry atmosphere. Two
In the humidity sensor for measuring the humidity by utilizing the fact that the heat dissipation of the temperature-sensitive resistor changes depending on the humidity and measuring the voltage drop of the first and second temperature-sensitive resistors, A crosslinked structure made of an electrically insulating thin film crosslinked on the recess of the substrate, the first temperature-sensitive resistor fixed inside or on the crosslinked structure, and a supporting leg for supporting the crosslinked structure. A humidity sensor having a member, wherein the cross-linked structure and the support leg member are H-shaped in overall shape. 2. A first temperature-sensitive resistor placed in a measurement atmosphere, a heating element for heating the first temperature-sensitive resistor by Joule heat to heat the first temperature-sensitive resistor, and a dry atmosphere. Second
And a voltage drop across the first and second temperature-sensitive resistors, utilizing that the heat dissipation of the first and second temperature-sensitive resistors changes depending on humidity. A humidity sensor for measuring humidity by measuring a crosslinked structure comprising an electrically insulating thin film crosslinked on the concave portion of a substrate having a concave portion, and the first fixed inside or on the crosslinked structure body. A temperature-sensitive resistor, the heating element fixed inside or on the cross-linked structure near the first temperature-sensitive resistor, and a supporting leg member supporting the cross-linked structure, Further, the humidity sensor, wherein the cross-linked structure and the supporting leg member have an H-shaped overall shape.