JPH11118748A - Moisture detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a moisture detector that is simple in configuration and at the same time can be adjusted easily. SOLUTION: Analog-vaue moisture output from a moisture sensor is converted into a digital value (S13), the moisture output is corrected based on a correction value being set to a potentiometer (S18), and a data table is searched and a moisture value is searched (S20). Then, the searched value is converted into a PWM signal (S22) and then is converted into an analog voltage value by a moisture output smoothing circuit. In this manner, since a moisture sensor value that changes logarithmically is processed digitally, an adjustment for coping with logarithmic characteristics is not required. Also, since the data table is used, it is not necessary to perform a complex arithmetic processing.

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 outputting a humidity value measured by a humidity sensor as a linear analog value.

[0002]

2. Description of the Related Art As a humidity sensor, a fixed electrolyte sensor for detecting humidity in the air based on a voltage or a current value at the time of absorbing and desorbing moisture in a porous material is used. In such a humidity sensor, the resistance value changes logarithmically with respect to humidity. FIG. 5 shows the relationship between the humidity and the resistance value. In the figure, measured values of the humidity sensor 1 and the humidity sensor 2 are shown. As described above, the sensor made of a porous ceramic or a polymer material has a feature that the output changes logarithmically and the characteristics are different for each unit.

For this reason, in a conventional humidity detecting device which outputs an analog value corresponding to humidity, for example, a voltage value which is linearly changed according to humidity, a voltage value corresponding to humidity is generated by a discrete analog circuit. Was. That is, a linear voltage value is output by approximating the logarithmic curve shown in FIG. 5 with a broken line or using a logarithmic amplifier.

[0004]

Here, the characteristics of the above-described humidity sensor made of porous ceramics or polymer materials deteriorate over time. That is, since moisture is absorbed and desorbed in the porous material, dust accumulates in the porous material, and the resistance value changes, making it impossible to measure accurately. For this reason, it is necessary to periodically replace the humidity sensor (for example, one year). However, since the humidity detection device that performs the conversion to the analog value is individually adjusted for each sensor, the humidity sensor is changed. Has been replaced with

Here, the analog circuit requires two kinds of adjustments, and it takes a long time to set. The two types are a characteristic adjustment for the output deviation of the humidity sensor and an adjustment for approximating the logarithmic characteristic change (logarithmic curve) of the humidity sensor by a polygonal line using an analog circuit on the humidity detection device side. That is, as shown in FIG. 5, the slopes (logarithmic curves) of the characteristic curves of the sensors 1 and 2 are almost similar, but are displaced in the vertical direction. For this reason, first, in order to realize a polygonal line approximation adapted to a logarithmic curve common to the humidity sensor, adjustment of several variable resistances in a humidity detection device composed of discrete components is performed. Further, it is necessary to perform adjustment in accordance with the characteristics of the individual humidity sensors, that is, adjustment so as to conform to the vertical output characteristics of the sensors 1 and 2 shown in FIG.

Therefore, the inventor of the present invention converts at least the output value from the humidity sensor into a digital value, performs an operation corresponding to the above-described polygonal line approximation, converts the output value into an analog value, and outputs the converted value. In addition, it was devised that the characteristic adjustment for realizing the polygonal line approximation on the humidity detection device side was eliminated.

However, in the case of digital processing, a relatively high-order microcomputer of about 16 bits is required in order to realize an operation equivalent to the broken line approximation, and an increase in cost is inevitable. Is expected. That is, it is required to use an expensive microcomputer for a humidity detecting device that is periodically replaced with a humidity sensor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a humidity detecting device having a simple configuration and easy adjustment.

[0009]

According to the present invention, in order to achieve the above object, in a humidity detecting apparatus according to the first aspect, analog / digital converting means for converting an analog humidity output from a humidity sensor into a digital value, Correction value setting means for setting a correction value for correcting the temperature dependency of the humidity sensor with the characteristics of the temperature sensor, a data table holding a data value corresponding to the humidity output converted into a digital value, and the correction value Search means for correcting the humidity output converted to a digital value by the digital-analog conversion means based on the correction value set in the setting means, searching the data table for the humidity value, and the search means And a digital / analog converting means for converting the value retrieved by the above into an analog value.

According to a second aspect, in the first aspect,
A technical feature is that the analog / digital conversion means, the data table, and the search means are constituted by a 4-bit microcomputer.

Further, according to claim 3, in claim 1 or 2, the search means outputs a humidity value obtained by searching the data table as a PWM signal, and the digital / analog conversion means smoothes the PWM signal. And generating an analog humidity value.

According to the first aspect of the present invention, the analog / digital conversion means converts an analog humidity output from the humidity sensor into a digital value, and the search means performs digital conversion based on the correction value set in the correction value setting means. -Correct the humidity output converted into a digital value by the analog conversion means, and search the data table to search for the humidity value. Then, the digital / analog conversion means converts the value searched by the search means into an analog value. As described above, in the first aspect, since the humidity sensor value that changes logarithmically is digitally processed, there is no need to make an adjustment to correspond to the logarithmic characteristic. Further, since a data table is used, there is no need to perform complicated arithmetic processing. Therefore, the output of the humidity sensor value can be realized with a simple configuration. Further, since the correction value for correcting the characteristics of the temperature sensor is set in the correction value setting means, an appropriate value can be output in accordance with the characteristics of each humidity sensor.

According to the second aspect, the analog / digital conversion means, the data table, and the search means use the data table when processing the output value of the logarithmically changing humidity sensor. (4-bit) microcomputer.

According to a third aspect of the present invention, the search means outputs the humidity value obtained by searching the data table as a PWM signal. Then, since the digital / analog conversion means generates the analog humidity value by smoothing the PWM signal, the conversion from the digital value to the analog value is easy.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a humidity detecting device according to the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration of a temperature and humidity detecting device 10 according to one embodiment of the present invention. The temperature and humidity detecting device 10 includes a humidity sensor 1 made of a porous ceramic or a polymer material such as a stabilized zirconia plate.
2, a potentiometer 14 for correcting the characteristics of the humidity sensor 12, a temperature sensor 16 composed of a platinum temperature sensor, a potentiometer 18 for correcting the characteristics of the temperature sensor 16, One microcomputer 20 capable of performing bit arithmetic processing and performing 10-bit A / D conversion;
From the PWM humidity signal from 0 to 1 as a humidity value
Humidity output smoothing circuit 30 that outputs an analog voltage value of 0 V
A temperature output smoothing circuit 32 for smoothing the PWM temperature signal from the microcomputer 20 to output an analog voltage value of 0 to 10 V as a temperature value, and a power supply circuit 34 for supplying power.

The microcomputer 20 includes the humidity sensor 12, the potentiometer 14 for correcting the humidity sensor,
A / D for analog-to-digital conversion of the output value of the temperature sensor 16 and the temperature sensor correction potentiometer 18
A conversion unit 22, a humidity data table 24 holding humidity values corresponding to the digital values converted by the A / D conversion unit 22, and a temperature holding temperature values corresponding to the converted digital values A data table 26, a humidity PWM control unit 26 for generating a PWM signal corresponding to a humidity value, and a temperature PWM control unit 2 for generating a PWM signal corresponding to a temperature value
9 is provided.

When the temperature and humidity detector 10 is shipped from a factory, the values of the potentiometers 14 and 18 are adjusted in accordance with the humidity sensor and the temperature sensor, respectively. This adjustment is performed by actually arranging the humidity sensor 12 and the temperature sensor 16 in a predetermined humidity and temperature adjustment room, and setting the potentiometer 14 and the potentiometer 14 so that a correct output value is obtained.
The adjustment is performed by setting an adjustment screw 18 not shown.

Here, the processing by the microcomputer 20 will be described with reference to the flowchart of FIG. Note that, in this description, the processing for calculating the humidity will be described, but the processing is similarly performed when calculating the temperature.

The microcomputer 20 obtains an output (analog voltage value or current value) from the humidity sensor 12 to obtain the humidity (S12). The value is converted to a digital value of 8 to 10 bits by the A / D converter 22 (S
13). Next, an adjustment value (analog value) set in the potentiometer 14 is read (S14). Thereafter, the A / D converter 22 converts the value into a digital value of 8 to 10 bits (S16). Thereafter, the output value of the humidity sensor 12 is corrected by adding the set value of the potentiometer 14 to the output value of the humidity sensor 12 (S
18). For example, if the humidity sensor output value converted to a digital value is 150 and the setting value of the potentiometer 14 is 10, the output value of the humidity sensor is corrected to 160 (see FIG. 3).

Subsequently, the microcomputer 20
The data value corresponding to the corrected output value (memory address) of the humidity sensor is searched with reference to the humidity data table 24 (S20). The configuration of the humidity data table 24 is shown in FIG. As shown in the figure, the data table is
The data value corresponding to the output value (memory address) of the humidity sensor is held in a table format. For example, for the output value (memory address) 160, the humidity is 60.3%.
Will be read out.

The microcomputer 20 has a humidity PWM
The control unit 26 generates a PWM signal corresponding to the data value (603 corresponding to 60.3% humidity) (S2).
2). This PWM signal will be described with reference to FIG. The PWM signal (output pulse) is output at regular intervals T, but the pulse width t is adjusted according to the humidity value. The microcomputer 20 outputs a digital value (PWM signal) obtained by correcting the output value of the humidity sensor 12 by the processing described above.

The PWM signal output from the microcomputer 20 is supplied to a humidity output smoothing circuit 30 as shown in FIG.
It is smoothed as shown in FIG. In other words, the humidity output smoothing circuit 30 supplies the voltage from 0 V to 1 according to the width of the PWM signal.
It outputs humidity voltage values up to 0V. Here, a voltage value corresponding to the above-mentioned humidity of 60.3% is output.

In this manner, the voltage value corresponding to the humidity value and the temperature value in the same manner are output from the temperature / humidity detecting device 10 to an air conditioner or the like (not shown) to adjust the room temperature and the like.

In this embodiment, since a PWM signal is transmitted as a digital output from the microcomputer 20, conversion into an analog value can be realized by the humidity output smoothing circuit 30 having a simple configuration using a capacitor or the like.

In order to process a humidity signal in an analog manner by a humidity detector as in the above-described prior art, it is necessary to perform a polygonal line approximation to convert the logarithmic output characteristic of the humidity sensor into a linear characteristic. . However, complicated adjustment was required to perform a polygonal line approximation in accordance with the characteristics of the humidity sensor. On the other hand, in the present embodiment, since the processing is performed digitally, there is no need to make an adjustment to correspond to the logarithmic characteristic of the humidity sensor. Furthermore, when an analog circuit is realized by discrete components, the circuit configuration is complicated and the manufacturing cost is high. On the other hand, in this embodiment, the one-chip 4-bit microcomputer 20
And the simple configuration of the humidity output smoothing circuit 30 and the temperature output smoothing circuit 29, there is an advantage that the temperature and humidity detecting device 10 can be manufactured inexpensively and small.

Further, when digital line approximation is realized by calculation as in the above-described analog processing as digital processing for coping with the logarithmic characteristic of the humidity sensor, the above-described unit adjustment is unnecessary, but very simple. Complicated calculations must be performed, and a high-performance (high-order) microcomputer is required. On the other hand, in the present embodiment, by searching the data table, it is possible to achieve the same accuracy as that of the approximation of the polygonal line approximation.

In the above-described embodiment, the temperature and humidity detecting device 10 for measuring humidity and temperature has been described as an example. However, it is needless to say that the present invention can be applied to a humidity detecting device for measuring only humidity. No. In the above embodiment, the PWM signal is output from the microcomputer 20 and converted into an analog value by the humidity output smoothing circuit provided outside the microcomputer 20, but the microcomputer is provided with a D / A converter. It is also possible.

In the above embodiment, the analog output value of the humidity sensor is converted into a digital value,
Convert the value of potentiometer 14 to digital value,
The output value of the humidity sensor was corrected, that is, the correction was performed digitally. Instead, the analog output value of the humidity sensor can be corrected by the analog value of the potentiometer 14, that is, the correction can be performed in an analog manner. Furthermore,
In the above-described embodiment, the voltage value corresponding to the humidity value is output as the analog output of the temperature / humidity detecting device 10, but a current value may be output instead.

Further, in this embodiment, a porous ceramic or polymer material is exemplified as the humidity sensor. However, according to the structure of the present invention, the output characteristic changes linearly even with a material other than the porous ceramic or polymer material. It can be applied when using various sensors that do not.

[0030]

As described above, according to the first aspect of the present invention, since the humidity sensor value that changes logarithmically is digitally processed, there is no need to make adjustments to correspond to the logarithmic characteristic. Further, since a data table is used, there is no need to perform complicated arithmetic processing. Therefore, the output of the humidity sensor value can be realized with a simple configuration. Further, since a correction value for correcting the characteristics of the temperature sensor is set in advance, it is possible to output an appropriate value according to the characteristics of each humidity sensor.

According to the second aspect of the present invention, when processing the output value of the humidity sensor which changes logarithmically, a data table is used. Therefore, these can be constituted by a microcomputer having a low-order bit number (4 bits). The detection device can be configured to be small and inexpensive.

According to the third aspect, since the PWM signal is smoothed to generate an analog humidity value, conversion from a digital value to an analog value is easy.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a temperature and humidity detecting device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing processing by a microcomputer.

FIG. 3 is an explanatory diagram showing a configuration of a humidity data table.

4 (A) is a waveform diagram showing a PWM signal from a humidity PWM control unit, and FIG. 4 (B) is a waveform diagram showing a state where the PWM signal shown in FIG. 4 (A) is smoothed; It is.

FIG. 5 is a graph showing characteristics of a humidity sensor.

[Explanation of symbols]

Reference Signs List 10 Temperature / humidity detector (humidity detector) 12 Humidity sensor 14 Potentiometer (humidity) (correction value setting means) 16 Humidity sensor 18 Potentiometer (correction value setting means) 20 Microcomputer (search means) 22 A / D Conversion unit (analog / digital conversion unit) 24 Humidity data table (data table) 26 Humidity PWM control unit 28 Temperature data table 29 Temperature PWM control unit 30 Humidity output smoothing circuit (digital / analog conversion unit) 32 Temperature output smoothing circuit (digital / Analog conversion means) 34 Power supply circuit

Claims (3)

[Claims] An analog-to-digital converter for converting a humidity output of an analog value from a humidity sensor into a digital value; a correction value setting unit for setting a correction value for correcting a characteristic of a temperature sensor; A data table that holds a data value corresponding to the converted humidity output, and based on the correction value set in the correction value setting means, corrects the humidity output converted to a digital value by the digital-analog conversion means. And a digital / analog converting means for converting the value searched by the searching means into an analog value. 2. The humidity detecting apparatus according to claim 1, wherein said analog / digital conversion means, data table, and retrieval means comprise a 4-bit microcomputer. 3. The method according to claim 1, wherein the search unit outputs a humidity value obtained by searching the data table as a PWM signal, and the digital / analog conversion unit smoothes the PWM signal to generate an analog humidity value. The humidity detecting device according to claim 1 or 2, wherein: