JPH06308067A - Humidity detector - Google Patents

Abstract

PURPOSE:To conduct detection operation and realize reliability improvement of humidity detection operation over a wide rane though an inexpensive humidity sensitive element is used. CONSTITUTION:Dewing sensors 2, 3 are equipped with humidity and resistance value characteristics wherein internal resistance values gradually increase in response to environmental humidity. A sensor circuit 1 composed of serial circuits of the dewing sensors 2, 3 different in operation characteristics generates detection voltage Vd indicating the characteristics which quietly increase and reduce in respose to a difference between the internal resistance values of the dewing sensors 2, 3 from a common connection point therebetween. A comparator 7 compares the detection voltage Vd transmitted from the sensor circuit 1 with reference voltage Vs transmitted from a reference voltage generation circuit 4, when Vd>=Vs is indicated, namely, when detection humidity shown with the sensor circuit 1 is operation start humidity or higher of a ventilating fan for a bath indicated with the reference voltage Vs, a detection signal Sa is produced.

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 atmospheric humidity by utilizing a humidity sensitive element whose internal resistance value changes according to the ambient humidity.

[0002]

2. Description of the Related Art A humidity detecting device required for automatic operation of a bathroom ventilation fan is generally constructed by using a humidity sensitive element whose internal resistance value changes according to the ambient humidity. It is something. Specifically, in this type of humidity detection device, a conversion circuit that converts the internal resistance value of the humidity sensing element into a voltage signal, and the voltage signal from this conversion circuit and the operation start humidity of the bathroom ventilation fan are supported. And a reference voltage that is set by the comparison circuit, and the comparison circuit is configured to automatically operate the bathroom ventilation fan when the voltage signal and the reference voltage have a predetermined relationship. It is configured to generate a sensing signal for control purposes.

[0003]

A relatively inexpensive element known as a condensation sensor is generally used as the humidity sensitive element whose internal resistance value changes in accordance with the ambient humidity. This dew sensor is composed of a resistance type polymer film humidity sensor and has a moisture sensitive resistance film made of a hygroscopic resin and a conductive material such as carbon particles, and the film swells due to the adsorption of humidity. This is based on the principle that the distance between carbon particles increases and the internal resistance value increases.

However, in such a humidity sensitive element, since the internal resistance value rapidly increases when the detected humidity reaches about 90%, the conventional humidity detecting device has a wide humidity range. There is a problem that the detection operation over the range becomes difficult, and it is impossible to precisely perform the automatic operation control of the bathroom ventilation fan. Further, in the conventional humidity detection device, when the characteristics of the humidity sensitive element are deteriorated by a solvent or gas, the voltage signal output from the conversion circuit is directly affected and the voltage signal fluctuates. Therefore, the humidity detection operation is unavoidably unstable, and the reliability is poor.

The present invention has been made in view of the above circumstances, and an object of the present invention is to use a relatively inexpensive moisture-sensitive element, while enabling a detection operation over a wide humidity range, and It is an object of the present invention to provide a humidity detecting device which has an effect of improving the reliability of the detecting operation.

[0006]

In order to achieve the above-mentioned object, the present invention provides a humidity detecting device constituted by using a humidity sensitive element whose internal resistance value changes according to the ambient humidity,
A sensor circuit, which is formed by connecting at least two humidity-sensitive elements having different operation characteristics in series, to which a constant voltage is applied, and a reference voltage generating circuit which generates a reference voltage are provided. A comparison means is provided which compares a detection voltage output from a connection point between predetermined humidity sensitive elements in the sensor circuit with the reference voltage and generates a detection signal when the two have a predetermined relationship. is there.

Further, in a humidity detecting apparatus constructed by using a humidity sensitive element whose internal resistance value changes according to the ambient humidity, the resistance values of two humidity sensitive elements having different operating characteristics are respectively converted into voltage signals. First and second conversion circuits for conversion, a differential amplifier circuit that outputs a voltage signal according to the difference between the voltage signals from the first and second conversion circuits, and a voltage from the differential amplifier circuit It is also possible to provide a determination means for generating a detection signal when the signal level reaches a predetermined state.

In such a configuration, the differential value of the humidity-resistance characteristic curve of one humidity-sensitive element at an arbitrary humidity is the same as the above-mentioned arbitrary humidity in the humidity-resistance characteristic curve of the other humidity-sensitive element. It is desirable that the bias voltage of a constant level be applied to at least one of the voltage signals output from the first and second conversion circuits as described above. Biasing means may be provided.

[0009]

In the humidity detecting device according to the first aspect of the present invention, since the operating characteristics of at least two humidity sensitive elements in the sensor circuit to which a constant voltage is applied are different, connection between predetermined humidity sensitive elements is performed. The detection voltage output from the point (corresponding to the humidity detected by the sensor circuit) has a characteristic of gradually increasing or decreasing in response to the change in the difference in the internal resistance values of those humidity sensitive elements. This makes it possible to detect a wide range of humidity. The comparison means compares the detection voltage with the reference voltage from the reference voltage generation circuit, and generates a detection signal when the two have a predetermined relationship. Therefore, if the reference voltage is set to a value corresponding to an arbitrary humidity in advance, a detection signal will be generated when the set humidity is reached.

In the humidity detecting device according to the second aspect of the present invention, the first and second conversion circuits output two types of voltage signals corresponding to the resistance values of the humidity sensitive elements having different operating characteristics. The differential amplifier circuit outputs a voltage signal corresponding to the difference between the above voltage signals as a signal corresponding to the detected humidity. The voltage signal thus output is 2
Since a characteristic of gradually increasing / decreasing in accordance with a change in the internal resistance value difference of each humidity sensitive element is exhibited, it becomes possible to detect a wide range of humidity by such a voltage signal. The determination means is the level of the voltage signal from the differential amplifier circuit,
That is, a detection signal is generated when the detected humidity reaches a predetermined state.

In the humidity detecting device according to the third aspect of the present invention, the differential value of the humidity-resistance characteristic curve of one humidity-sensitive element at an arbitrary humidity is the humidity-resistance characteristic curve of the other humidity-sensitive element. Since it is selected so as to be always larger than the differential value at the arbitrary humidity, the difference between the respective voltage signals output from the first and second conversion circuits gradually increases as the detected humidity changes. The characteristic of increasing and decreasing is exhibited, and as a result, the humidity detection operation is ensured.

In the humidity detecting device according to the fourth aspect, since a bias voltage of a constant level is applied to at least one of the voltage signals output from the first and second conversion circuits, An arbitrary difference can be given between the voltage signals output from the first and second conversion circuits, and the humidity detection operation can be performed more reliably.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. In FIG. 1 schematically showing an electrical configuration, a sensor circuit 1 for detecting atmospheric humidity is configured by connecting two dew condensation sensors 2 and 3 as humidity sensitive elements in series. In this case, the dew condensation sensor 2
2 and 3 are constituted by, for example, a resistance type polymer film humidity sensor, and as shown in FIG. 2, they have a humidity / resistance value characteristic in which the internal resistance value gradually increases according to the ambient humidity. It has a characteristic that the internal resistance value rapidly increases when the ambient humidity exceeds about 90%. Incidentally, FIG.
As is clear from the above, as the dew condensation sensors 2 and 3, those having different operation characteristics, that is, humidity / resistance value characteristics are used.

The sensor circuit 1 has a constant voltage power supply terminal + V.
The dew condensation sensor 2
From the common connection point between Nos. 3 and 3, the detection voltage Vd having a voltage value corresponding to the internal resistance values (and thus the detection humidity) of the dew condensation sensors 2 and 3 is output. Above detection voltage V
When the humidity / resistance value characteristics of the dew condensation sensors 2 and 3 are as shown in FIG. 2, d changes with respect to the detected humidity as shown in FIG. That is, as is apparent from FIG. 3, the detection voltage Vd is equal to the dew condensation sensors 2 and 3.
2 shows a characteristic of gradually increasing / decreasing in accordance with a change in the difference in internal resistance value of the dew condensation sensors 2 and 3 shown in FIG.
Humidity at which each characteristic curve of each humidity and internal resistance of
5%), constant voltage power supply terminal + 1 of Vcc output voltage
It will take on a value of / 2.

The reference voltage generating circuit 4 has a constant voltage power supply terminal +
The resistors 5 and 6 for voltage division are connected in series between Vcc and the ground terminal, and the reference voltage Vs is generated from the common connection point between the resistors 5 and 6. The reference voltage Vs is set so as to have a value corresponding to the operation start humidity of the bathroom ventilation fan, which is a load.

The comparator 7 as a comparison means is an open collector type, and its output terminal is a pull-up resistor 8
Is connected to the constant voltage power supply terminal + Vcc via the, and when the detection voltage Vd and the reference voltage Vs have a relationship of Vd ≧ Vs, that is, the humidity detected by the sensor circuit 1 is for the bathroom The detection signal S consisting of a high level signal when the humidity exceeds the operation start humidity of the ventilation fan.
a is generated through the output terminal 7a.
When the detection signal Sa is output, control for starting the operation of the bathroom ventilation fan is performed.

According to the above-described embodiment, the humidity detected by the sensor circuit 1 exhibits a characteristic that the humidity gradually increases and decreases in response to the change in the difference between the internal resistance values of the dew condensation sensors 2 and 3, so that a wide humidity range is obtained. It is possible to perform the detection operation over the range, and thus it is possible to finely control the automatic operation of the bathroom ventilation fan that is the load. Further, the sensor circuit 1 is
Since the two dew condensation sensors 2 and 3 are connected in series and the detection voltage Vd corresponding to the detected humidity is obtained from a common connection point between the dew condensation sensors 2 and 3, Even if the characteristics are deteriorated by solvent or gas, the relative output characteristics of the dew condensation sensors 2 and 3 are relatively stable, and the reliability of the humidity detection operation of the sensor circuit 1 is improved. . Moreover, in the present embodiment, in forming the sensor circuit 1 having the above-mentioned output characteristics, the dew condensation sensors 2 and 3 which are relatively inexpensive are formed.
Since it is only necessary to provide the above, it becomes possible to suppress the overall cost increase as much as possible.

In the above embodiment, the sensor circuit 1 is configured by the two dew condensation sensors 2 and 3, but the sensor circuit may be configured by connecting a larger number of dew condensation sensors in series. it can.

FIGS. 4 to 6 show a second embodiment of the present invention, and only the parts different from the first embodiment will be described below. That is, in FIG. 4, the first conversion circuit 9 converts the internal resistance value of the condensation sensor 2 into a voltage signal V1 and outputs the voltage signal V1, and the second conversion circuit 10 converts the internal resistance value of the condensation sensor 3 into a voltage signal V1. Convert to V2 and output. As the dew condensation sensors 2 and 3, as shown in FIG. 2 used in the description of the first embodiment, the differential value at the arbitrary humidity in the humidity / resistance value characteristic curve of one dew condensation sensor 3 is the other. Is selected so that it is always larger than the differential value of the humidity / resistance value characteristic curve of the dew condensation sensor 2 at the above arbitrary humidity.

Bias adding circuit 1 as bias means
1 applies a constant level bias voltage ΔV to the voltage signal V2 output from the second conversion circuit 10, for example, and accordingly, the voltage signals V1 and V2.
Have a relationship as shown in FIG. This makes it possible to reliably set the level of the voltage signal V2 having a large differential value at arbitrary humidity to be always higher than the level of the voltage signal V1. As a result, the voltage difference between the two is high. It will grow as it grows.

On the other hand, the differential amplifier circuit 12 outputs a voltage signal V3 corresponding to the difference between the voltage signals V1 and V2, and the voltage signal V3 is the humidity / resistance value characteristic of the dew condensation sensors 2 and 3. 2 is as shown in FIG. 2, the detected humidity changes as shown in FIG. That is, the voltage signal V3 exhibits a characteristic that the voltage signal V3 gradually increases / decreases in accordance with the change in the difference between the voltage signals V1 and V2. The differential amplifier circuit 12 is a concept including one having an amplification factor of "1".

The discriminating circuit 13 as a discriminating means is operated when the level of the voltage signal V3 from the differential amplifier circuit 12 reaches a predetermined state (for example, a level corresponding to the operation start humidity of the bathroom ventilation fan). The output control circuit 14 generates the detection signal Sa.

Therefore, also in the second embodiment described above,
Since the voltage signal V3 indicating the detected humidity has a characteristic of gradually increasing or decreasing in response to a change in the difference in internal resistance values of the dew condensation sensors 2 and 3, it is possible to perform a detecting operation over a wide humidity range. It becomes possible to finely control the automatic operation of the bathroom ventilation fan, which is a load. Further, since the voltage signal V3 is a signal according to the difference between the voltage signals V1 and V2, it is less likely to be adversely affected when the characteristics of the dew condensation sensors 2 and 3 are deteriorated by a solvent, gas, etc. The reliability is improved and the common mode noise is canceled, so that the malfunction can be suppressed. Of course, also in this embodiment, since it is only necessary to provide the relatively inexpensive dew condensation sensors 2 and 3, it is possible to suppress an increase in the overall cost as much as possible.

Since the bias adding circuit 11 in the second embodiment is necessary when the humidity / resistance characteristic curves of the dew condensation sensors 2 and 3 cross each other, it may be omitted in some cases. . Further, even when the humidity / resistance value characteristic curves of the dew condensation sensors 2 and 3 intersect, the voltage output from the first and second conversion circuits 9 and 10 is changed by making them different. When the characteristic curves of the signals V1 and V2 are configured not to cross each other, the bias adding circuit 11 can be omitted.

[0025]

As apparent from the above description, according to the present invention, by using at least two humidity sensitive elements having different operating characteristics, the detection output with respect to humidity can be gradually increased and decreased over a wide range. Since it is configured, a relatively inexpensive moisture-sensitive element is used, but it has an excellent effect of enabling detection operation over a wide humidity range, and the characteristics of the moisture-sensitive element deteriorate. Even in this case, the adverse effect on the detection output can be reduced, and the reliability of the humidity detection operation can be improved.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a humidity / resistance value characteristic curve of a dew condensation sensor.

FIG. 3 is a diagram showing output characteristics of a sensor circuit.

FIG. 4 is an electrical configuration diagram showing a second embodiment of the present invention.

FIG. 5 is a diagram showing output characteristics of first and second conversion circuits.

FIG. 6 is a diagram showing output characteristics of a differential amplifier circuit.

[Explanation of symbols]

In the drawing, 1 is a sensor circuit, 2 and 3 are dew condensation sensors (moisture sensitive elements), 4 is a reference voltage generation circuit, 7 is a comparator (comparing means), 9 is a first conversion circuit, and 10 is a second conversion circuit. ,
Reference numeral 11 is a bias addition circuit (bias means), 12 is a differential amplifier circuit, and 13 is a determination circuit (determination means).

Claims (4)

[Claims] 1. A humidity detecting device comprising a humidity sensitive element whose internal resistance value changes according to the ambient humidity, wherein at least two humidity sensitive elements having different operating characteristics are connected in series. A sensor circuit in which a constant voltage is applied to these series circuits, a reference voltage generation circuit for generating a reference voltage, a detection voltage output from a connection point between predetermined humidity sensitive elements in the sensor circuit, and the reference voltage. And a comparing means for generating a detection signal when the two have a predetermined relationship with each other. 2. A humidity detecting device configured by using a humidity-sensitive element whose internal resistance value changes according to ambient humidity, wherein resistance values of two humidity-sensitive elements having different operating characteristics are respectively converted into voltage signals. First and second conversion circuits for conversion, a differential amplifier circuit that outputs a voltage signal according to the difference between the voltage signals from the first and second conversion circuits, and a voltage from the differential amplifier circuit A humidity detecting device, comprising: a determination unit that generates a detection signal when the signal level reaches a predetermined state. 3. A humidity / resistance value characteristic curve of one humidity sensitive element at a given humidity is always larger than a humidity / resistance value characteristic curve of the other humidity sensing element at a given humidity. The humidity detecting device according to claim 1, wherein the humidity detecting device is selected as follows. 4. A bias means for applying a bias voltage of a constant level to at least one of the voltage signals output from the first and second conversion circuits is provided. Humidity detector.