JPH01259406A - Temperature and humidity controller - Google Patents

Abstract

PURPOSE:To realize a thermo-hygrostat of high precision by using a temperature sensor and an absolute humidity sensor to control the temperature and the humidity independently of each other. CONSTITUTION:A thermo-sensitive element Ths which is set to the heated state by power supply is used, and the change of the heat conductivity of air based on the moisture content is detected by the temperature change of the thermo-sensitive element Ths to obtain an absolute humidity signal. A relative humidity signal is obtained by the operation based on the absolute humidity signal obtained in this manner and the temperature signal obtained from the temperature measuring part Ths. The obtained absolute humidity signal or relative humidity signal is compared with its set value, and a power control part is controlled in accordance with the error signal to perform humidification, thereby controlling the absolute humidity or the relative humidity in the thermo- hygrostat. Thus, the thermo-hygrostat is stable and has a high precision, and especially, the atmosphere at a high temperature and a high humidity is easily realized.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a device for controlling temperature and humidity in a constant temperature and humidity chamber, and in particular, a temperature and humidity control device suitable for a constant temperature and humidity chamber with high temperature and high humidity. It is related to the device.

[Conventional technology]

Many types of constant temperature and humidity chambers are commercially available as environmental test devices for testing the temperature and humidity characteristics of electronic components and various materials.

Conventionally, a humidity sensor using a temperature sensor such as a platinum 11 temperature body, a thermocouple, or a thermistor temperature sensor has been used as a humidity sensor to control humidity in a constant temperature and humidity chamber. A commonly used method is to calculate the relative humidity from the temperature difference between the wet bulb and the wet bulb to control humidity. For information on how to calculate humidity using the psychrometric method, see
It is well known by JIS8806.

Humidity sensors other than the dry-wet-bulb type include resistance-type and capacitance-type humidity sensors that utilize changes in electrical characteristics due to moisture absorption. These include electrolyte-based lithium chloride humidity sensors, organic-based polymer film humidity sensors, and total oxide-based ceramic humidity sensors.

In addition, as a control method for a constant temperature and humidity chamber using such a humidity sensor, a method is generally used in which the temperature signal of the psychrometric method is converted into a relative humidity signal, and this signal is used to control the relative humidity inside the chamber. It is being said.

[Problem to be solved by the invention]

Recently, environmental test equipment is often required to operate under harsh conditions of high temperature and high humidity. Therefore, among conventional humidity sensors, those that utilize changes in electrical characteristics due to moisture absorption have problems in terms of reliability such as reproducibility, stability, responsiveness, and compatibility. Rarely used.

Therefore, a psychrometric humidity sensor is generally used as a humidity sensor in a constant temperature and humidity chamber.

However, since wet-psychrometric humidity sensors use gauze and water for the wet bulb, errors are likely to occur due to dirt on the gauze or water scale on the surface of the wet bulb, which requires careful handling and is cumbersome to maintain.

Furthermore, the error increases in areas of low temperature and low humidity.

The present invention is an attempt to solve the problems of the prior art, and is capable of highly accurate humidity measurement by using an absolute humidity sensor using a thermistor, platinum, etc. as a humidity sensor in a constant temperature and humidity chamber. It aims to make it possible.

Furthermore, with the conventional method of controlling relative humidity by converting the temperature signal of the wet-psychrometric method into a relative humidity signal, it is difficult to obtain good control results because both the dry-bulb temperature and the wet-bulb temperature affect the control results. In recent years, attention has been drawn to the fact that the temperature is very low, and as a solution to this problem, methods of controlling using dew point and temperature or absolute humidity and temperature are being considered.

The present invention uses a temperature sensor and an absolute humidity sensor to independently control a constant temperature and humidity chamber.
The aim is to realize a highly accurate constant temperature and humidity chamber.

[Means to solve the problem]

In order to achieve the above object, the temperature and humidity control device of the present invention has the following features:
In a constant temperature and humidity chamber that controls the temperature and humidity of the internal atmosphere to desired values, a temperature measuring section (11, 12, 13° 14), and a humidity measuring section (21, 22, 23,
25), a setting section (17, 17A) for setting temperature and absolute humidity or relative humidity, and a temperature control section for generating a temperature control signal by comparing the measured temperature of the temperature measuring section and the set temperature of the setting section. (16), heating means (18, 19) that heats the inside of the tank according to the temperature control signal, and a humidity control signal that compares the measured humidity of the humidity measuring section and the set humidity of the setting section. It includes a humidity control section (28) that generates humidity, and humidification means (29, 30) that humidifies the inside of the tank according to the humidity control signal.

[For production]

In the temperature and humidity control device of the present invention, a thermosensitive element such as a thermistor or platinum is used as a sensor to heat it by energizing it, and changes in the thermal conductivity of air based on the water vapor content are measured by Obtain the absolute humidity signal by detecting the temperature change. This method of measuring humidity is
This has already been proposed by the applicant (Patent Application No.
No. 4858 “Method for Measuring Humidity”, Utility Model Application No. 1981-8109
No. 2 “absolute humidity needle”).

Alternatively, a relative humidity signal is obtained by performing calculations from the absolute humidity signal obtained in this way and a temperature signal obtained separately.

The absolute humidity signal or relative humidity signal obtained in this way is compared with each setting value, and the power control unit is controlled according to the error signal to perform humidification, thereby controlling the absolute humidity in the constant temperature and humidity chamber. Alternatively, the relative humidity is controlled and the absolute humidity or relative humidity measurement value is displayed.

Furthermore, the temperature signal obtained by the temperature sensor is compared with the set value, and the power control unit is controlled according to the error signal to perform heating, thereby controlling the temperature in the constant temperature and humidity chamber. Display the measured values.

〔Example〕

A case where a thermistor is used as the heat-sensitive element will be described below.

FIG. 2 shows the configuration of an absolute humidity detection circuit according to an embodiment of the present invention, where E is a power supply, R1-R1 are fixed resistors, Ths is a thermistor for humidity detection, and The is a temperature compensation circuit. Thermistors a and b are output terminals.

The thermistor T h, S is for detecting absolute humidity and is held in a container with a ventilation hole so that it can freely contact the outside air. The thermistor The is for temperature compensation for humidity measurement results,
It has the same structure as the humidity detection thermistor ThS, but a thermistor with the same characteristics as the thermistor Ths is kept in an absolutely dry state in a container without ventilation holes. fixed resistance R,
, R2 form a bridge circuit together with the humidity detection thermistor T h s and the temperature compensation thermistor The. A current is passed through the bridge circuit from the power supply E through the current limiting fixed resistor R3, and the thermistors T゛hs, Th
Let e be heated to about 200″C.

If the humidity detection thermistor Ths is placed in an absolutely dry atmosphere, the bridge circuit will be in a balanced state and the terminal a
, b is zero. On the other hand, if the thermistor Ths for humidity detection is placed in an atmosphere containing water vapor, that is, humid air, the thermal conductivity of the gas constituting the atmosphere has changed from that in an absolutely dry state, so the thermistor Ths
As the temperature changes, the resistance changes, and the balance of the bridle is disrupted, producing an output voltage Vm across the load resistor R4 at terminals a and b. When the amount of water vapor in the atmosphere changes, the thermal conductivity also changes. In this way, an output voltage proportional to the amount of water vapor in the atmosphere, that is, the absolute humidity (g/m3) can be obtained as the bridge output.

Figure 3 shows the bridge output voltage Vm (mV) - absolute humidity (g/m3) in the absolute humidity detection circuit shown in Figure 2.
This figure shows an example of measuring the characteristics of up to the saturation state at each temperature.

Further, FIG. 4 shows an example of the output characteristics of the absolute humidity detection circuit shown in FIG. 2, in which outputs for each absolute humidity when the ambient temperature is 100° C. are calculated from experimental results.

In FIG. 3, in an atmosphere below 62° C., the curve from an atmosphere with zero humidity to a saturated state forms a parabolic rising curve. However, in an atmosphere of 62°C or higher, the absolute humidity has a maximum value around 140 g/m3, and as the absolute humidity increases further, the output voltage draws a downward curve, and when the absolute humidity exceeds 345 g/m3, the output voltage decreases. The polarity is reversed. This phenomenon was experimentally discovered by the inventors [April 3, 1980].

Japan Society of Applied Physics (University of Yamanashi) ``Measurement of Humidity''; July 1980, 20th 5ICE Academic Lecture (Tohoku University) ``Output Characteristics of Humidity Sensors'']. However, regarding this phenomenon, no theory has been made to date regarding the relationship between the amount of water vapor and the physical properties of the gas containing it.

If an absolute humidity detection circuit having the characteristics shown in FIG. 3 is used, there will be two absolute humidity values corresponding to the same bridge output voltage at an ambient temperature of 62° C. or higher.

Now, if the characteristics shown in Fig. 3 are the standard characteristics of the bridge output versus absolute humidity, the output Vm of the humidity sensor will be the temperature t(''
C) and absolute humidity (g/m3), so Vm,=f (x, t). Expressing this using an approximate formula, Vm= (Ax2+13x+c) ・ (Cu2 +
Dt+E). In the above equation, A-E is a constant determined from the output characteristic curve of FIG. 3, and the second term (Ct2+I)t+E) indicates a correction term due to temperature. Now g(t)-(Ct
2+D t +E), and from the above formula, the absolute humidity x (
g/m3) is calculated as follows.

Here, equation (1) corresponds to the region I in FIG. 3, and is expressed by adding an index 1 to represent the value in this region. Further, equation (2) corresponds to the range in which the output voltage is positive in the region H in FIG. 3, and is expressed using index 2. Furthermore, equation (3) corresponds to a range in which the output voltage is negative in the region H in FIG. 3, and is expressed using index 3.

For the characteristics shown in Figure 3, the absolute humidity x - 140g/m
It is shown that the bridge output is maximum when the number is 3.

Figure 5 shows the temperature t ("c) and the saturated absolute humidity xs (g/m
3), and since absolute humidity does not exceed 140 g/m3 at temperatures below 62°C, (
1) Absolute humidity Xi can be determined by formula. If the temperature is 62°C or higher, the absolute humidity is 140g.
Since the output voltage Vm shows an increasing curve until it reaches /m3, the absolute humidity Since the output voltage Vm shows a decreasing curve, the absolute humidity x2 can be determined using equation (2).Furthermore, in the high humidity region of 345 g/m3 or higher, the scratchiness of the output voltage Vm becomes negative, and is a function only of humidity. as (
3) Absolute humidity x3 can be determined by formula.

Further, in commonly used constant temperature and humidity chambers, the humidity setting 2 is often displayed using relative humidity. However, it is preferable to use an absolute humidity signal as the humidity control signal and humidity detection signal in a constant temperature and humidity chamber.
It becomes necessary to convert between relative humidity (%) and absolute humidity (g/m').

Now, if the saturated absolute humidity is xs, then po - standard pressure es - saturated water vapor pressure t - temperature (°C) On the other hand, relative humidity H (%) is therefore controlled by using the relative humidity as the set value. , the absolute humidity X, ~ with the absolute humidity at that time as the target value
All that is required is to control x3.

The mutual conversion between relative humidity (%) and absolute humidity (g/m3) can be calculated using the data in FIG. 5 and the relationship in equation (5).

FIG. 1 shows an embodiment of the present invention, and is a block diagram showing the configuration of a temperature/humidity control device of the present invention in which humidity is set using relative humidity. In this embodiment, a thermistor is used as a temperature and humidity sensing element. All of these sensing elements are mounted in the controlled atmosphere in a constant temperature and humidity chamber, and constitute a measurement circuit together with an electronic circuit mounted in the temperature and humidity control device.

In Figure 1, a thermistor T for temperature detection in a constant temperature and humidity chamber
The temperature detection signal from ht is converted into a voltage signal in the temperature signal-electrical signal converter 11.

This signal is amplified by an amplifier 12, converted to a digital signal by an analog/digital (A/D) converter 13, and a temperature display value (°C) is calculated by a temperature calculation section 14 of the microcomputer. This value is displayed on the display section 15 and is also sent to the temperature control section 16. On the other hand, the control target temperature in the constant temperature and humidity chamber is set in the setting section 17, and the temperature control section 16 compares the set temperature and the detected temperature, performs PID control according to the error signal, and outputs the temperature control signal. Occur. The power control unit 18 controls the power supplied to the warmer 19 according to the temperature control signal, and
This generates heat and raises the temperature inside the constant temperature and humidity chamber. The temperature detection thermistor Tht detects the changed temperature, and as a result, cycle temperature control is performed, and the temperature inside the tank converges to the set value.

Further, the humidity detection signal from the humidity detection thermistor Th 3° temperature compensation thermistor The of the constant temperature and humidity chamber is converted into a voltage signal in the humidity signal-electrical signal converter 21 consisting of the absolute humidity detection circuit shown in FIG. converted. This signal is amplified in an amplifier 22 and converted into an analog digital (A
/D) is converted into a digital signal by the converter 23.

This signal is applied to the absolute humidity calculating section 25 of the microcomputer via the absolute humidity characteristic region determining section 24, and the absolute humidity (g/m3) is calculated. Further, the absolute humidity-relative humidity calculation section 26 calculates relative humidity (%) from the absolute humidity and temperature, and the relative humidity is thereby displayed on the display section 15. On the other hand, the control target relative humidity in the constant temperature and humidity chamber is set in the setting section 17, and the relative humidity-to-absolute humidity conversion B27 converts this into absolute humidity and inputs it to the humidity control section 28. The humidity control section 28 compares the set humidity and the detected humidity, performs PID control according to the error signal, and generates a humidity control signal.

The power control unit 29 intermittents the power supplied to the humidifier 30 according to the humidity control signal, and the humidifier 30 thereby generates water vapor to increase the humidity in the constant temperature constant bath li1. Humidity detection thermistor The, temperature compensation thermistor ThC
detects the changed humidity, and a cycle of humidity control is performed based on this, and the humidity in the tank converges to the set value.

In this case, the absolute humidity-relative humidity calculation section 26. Relative humidity -
The mutual conversion between absolute humidity and relative humidity in the absolute humidity converter 27 requires a temperature signal as known from equation (41, (5)), so the temperature signal (°C) is sent from the temperature calculator 14. A signal can now be added.

FIG. 6 is a flowchart illustrating the determination operation in the absolute humidity characteristic region determination section 24. In this case, the determination is made by first checking the atmospheric temperature t in the tank (step Sl) and determining whether t<
62 ('C), it means that the determination that the absolute humidity is in the 1 area of 140 g/m3 or less has been carried out, so go to (2). t≧62 (.

In the case of C), it is necessary to determine whether it is in the l area or the ■ area, but this is done according to the logic shown in Figure 7, taking advantage of the fact that humidity control in this embodiment is performed by turning on and off the humidifier power supply. Make a judgment.

That is, whether the switch in the power control unit 29 that supplies power to the humidifier 30 is in the 0 (humidification stop) state or 1
(humidifying) state (step 32), and if humidifying, the output voltage Vm of the absolute humidity detection circuit is measured twice at a fixed short time interval, and the measured value Vm" (
Check Vm” (previously measured value) and Vm” (currently measured value), and
>Vmn-1 (increase), it is the l area, so go to ■(
Step S3), if humidification is stopped, check the output voltage Vm of the absolute humidity detection circuit, and if Vmn≦Vmn-' (decrease), it is in the l range, so go to ■ (step S4)
. If Vmn≦Vmn l (decrease) in step S3 and Vmn>Vmn-1 (increase) in step S4, it is determined that the area is ■, so output absolute humidity +4 again and check the output voltage ■τn of the circuit. If 0≦Vm, go to ■; if Vm<Q, go to ■ (Step S5)
.

In the case of {circle around (2)} in which the I area in FIG. 3 has been determined, the absolute humidity calculating section 25 performs a process of solving equation (1) to obtain the absolute humidity Xl. In the case of ■ in which the output voltage range of the area ■ in FIG. 3 has been determined, the absolute humidity calculation unit 2
In step 5, a process is performed to solve equation (2) and obtain the absolute humidity x2. In the case of (2) in which the negative range of the output voltage in the (2) region in FIG.

FIG. 8 shows another embodiment of the present invention, in which the same parts as in the embodiment shown in FIG. 1 are designated by the same numbers, and 15A is a display section;
17A is a setting section.

In the embodiment shown in FIG. 8, humidity is displayed and set using absolute humidity. Therefore, both the display of humidity in the display section 15A and the setting of humidity in the setting section 17A are performed using absolute humidity. Therefore, in the embodiment of FIG. 1, the absolute humidity-relative humidity converter 26
7 is no longer necessary, and the configuration is simplified.

According to the temperature and humidity control device of the present invention, it is possible to actually control temperature and humidity up to a saturated absolute humidity of 588 g/m3 within a range of atmospheric temperature in a constant temperature and humidity chamber up to around 100°C near O''CC. .

In conventional constant temperature and humidity chambers, both display and setting are often performed using relative humidity (%), and a wet/dry bulb type is often used for humidity detection. As a result, the control operation became complicated and highly accurate control could not be performed.However, in the present invention, absolute humidity is used for both humidity detection and control, so humidity can be controlled independently of temperature control. This makes it possible to perform highly accurate temperature and humidity control.

Furthermore, since a humidity detection element using a thermistor can be used, it is stable even in a high temperature and high humidity atmosphere, and the life of the device is long.

〔Effect of the invention〕

As explained above, according to the present invention, various troubles caused by gauze and water in the psychrometric bulb type hygrometer used for humidity measurement in conventional constant temperature and humidity chambers are freed, and the present invention is stable and highly accurate. Since it is possible to provide a constant temperature and humidity chamber that can easily create an atmosphere of high temperature and high humidity, it is suitable for use as an environmental test device.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing the configuration of an absolute humidity detection circuit according to an embodiment of the present invention, and FIG. 3 is an absolute humidity detection circuit shown in FIG. 2. Figure 4 is a diagram showing the output of the thermistor absolute humidity sensor at 100°C, Figure 5 is a diagram showing the relationship between temperature and saturated absolute humidity, and Figure 6 is a diagram showing the relationship between temperature and saturated absolute humidity. FIG. 7 is a flowchart illustrating the determination operation in the absolute humidity characteristic region determination section, FIG. 7 is a diagram showing the absolute humidity characteristic region determination logic, and FIG. 8 is a diagram showing another embodiment of the present invention. 11...-Temperature signal--electrical signal converter 12.21--Amplifier 13.23--Analog-digital (A/D) converter I4--Temperature calculation section 15, 15A--Display section 16-- Temperature control section 17, 17A - General setting section 18.29 - Power control section I9 - Warmer 21 - Humidity signal - Electrical signal conversion section 24 - Absolute humidity characteristic area determination section 5 - Absolute humidity Calculating unit 26 - Absolute humidity - relative humidity calculating unit 27 - Relative humidity - Absolute humidity converting unit 28 - Humidity control unit 30 - Humidifier patent applicant Shibaura Electronics Manufacturing Co., Ltd. Agent
Patent attorney Gobe Tamamushi (2 others) 11! Figure 2 shows the configuration of the humidity detection circuit Figure 2 shows the characteristics of IA vs. humidity Figure 3 shows the relationship between temperature and saturation 18 vs. humidity Figure 5 Whistle M! Diagram No. 7 shows the logic for determining the top area of the humidity sign.
mouth

Claims (3)

[Claims] (1) In a constant temperature and humidity chamber that controls the temperature and humidity of the internal atmosphere to desired values, a temperature measuring section that converts the signal from the temperature detection element installed in the chamber into an electrical signal and then into a temperature signal. (11,
12, 13, 14), and a humidity measurement unit (2) that converts the signal from the humidity detection element provided in the tank into an electrical signal and further converts it into an absolute humidity signal.
1, 22, 23, 25), a setting section (17, 17A) for setting temperature and absolute humidity or relative humidity, and a temperature control signal by comparing the measured temperature of the temperature measuring section and the set temperature of the setting section. a temperature control section (16) that generates a
, 19), a humidity control section (28) that compares the measured humidity of the temperature measuring section and the set humidity of the setting section and generates a humidity control signal, and a humidifier that humidifies the inside of the tank in accordance with the humidity control signal. Means (29
, 30). (2) A claim characterized in that the humidity measuring section uses a heat-sensitive element such as a thermistor in a heated state as a humidity detection element, and obtains an electrical output of absolute humidity proportional to the amount of moisture in the atmosphere inside the tank. The temperature and humidity control device according to item 1. (3) The humidity control section determines the absolute humidity range to be controlled by calculating the absolute humidity (g/m^3, X axis) - humidity measuring section electrical output (
absolute humidity (mV, Y axis) corresponding to the maximum point on the curve
The range below g/m^3) is defined as the first region, and the range above the absolute humidity equivalent to the maximum point (g/m^3) is defined as the second region, and it is determined which of these two regions it belongs to. 3. The temperature and humidity control device according to claim 1, further comprising a determining means (24).