JPS6248845B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for stably and highly accurately controlling the temperature and humidity of a constant temperature and humidity chamber.

A high-precision constant temperature and humidity chamber is equipped with a heater, etc., used to control the temperature inside the chamber, and a humidifier, which is heated by a heater, etc. for controlling the chamber humidity, and generates water vapor. For the purpose of detecting the relative humidity in the tank, a dry bulb temperature sensor with a dry temperature detection part and a wet bulb temperature sensor with a gauze or the like wrapped around the temperature detection part with one end immersed in water are installed. Then, based on the output of both the dry bulb and wet bulb temperature sensors, perform the calculation shown in the following formula,
At the same time as determining the relative humidity RH, the temperature is determined according to the output of the dry bulb temperature sensor, and the heater and humidifier are controlled.

RH=e/ _eS ×100(%) ………(1) e=e _W −A・P(1+T _W /C)(T _D −T _W ) Dependency, T _D :Dry bulb temperature, T _W : wet bulb temperature, e _S : saturated water vapor pressure at T _D (mmHg) e _W : T _W 〃 〃 (〃) P: Air pressure (mmHg) A: Parameter related to wind speed = 0.000656 (wet bulb does not freeze, and when the wind speed is 2.5 (m/s) or more) C: constant = 610 (when the wet bulb does not freeze) However, for example, the set relative humidity [hereinafter referred to as SP
(RH)] is 100%, and if the relative humidity in the tank [hereinafter referred to as PV(RH)] is less than SP(RH), the humidifier is powered on and starts humidification. , thermal energy is also generated at the same time as water vapor is generated, and the temperature inside the tank [hereinafter referred to as PV (T _D )] rises, so PV (RH) does not reach SP (RH).
The power to the humidifier remains on.

That is, at this time, if PV (T _D ) exceeds the set temperature in the tank [hereinafter referred to as SP (T _D )], the power to the heater is immediately cut off, but the thermal energy generated by the humidifier causes the PV (T _D ) continues to rise, causing a "thermal runaway phenomenon."

Therefore, in conventional control methods, PV
(T _D ) tends to rise abnormally, a "thermal runaway phenomenon," and PV (RH) also becomes unstable and unstable.
It had the disadvantage that PV (T _D ) and PV (RH) could not be controlled.

The present invention has the purpose of fundamentally solving such drawbacks of the conventional art, and sets the switching temperature close to SP(T _D ), and when PV(T _D ) becomes equal to or higher than the switching temperature,
PV(T
_D ) is switched to SP (T _D ), and the apparent PV (T _D ) becomes
By assuming that SP (T _D ) has been reached, the connection between the wet bulb temperature T _W and the dry bulb temperature T _D is severed, and the PV
The present invention provides an extremely effective method and device for controlling a constant temperature and humidity chamber that can stably control (T _D ) and PV (PH).

The details of the present invention will be explained below with reference to block diagrams showing embodiments.

In the same figure, the comparator CP has _a switching temperature signal CH ( _{T D} ) S and the output of the dry bulb temperature sensor
PV(T _D )S is given, the comparator CP compares the two, and the output PV(T _D )S is the switching temperature signal.
When CH(T _D )S or more is reached, a comparison output is generated and the switch SW is controlled to perform a switching operation.

In addition, the switch SW outputs the output PV via the amplifier A.
(T _D ) PV (RH) calculation section before switching S
Although it is given to OP ₁ , after the switching operation, the set temperature signal SP set by a potentiometer etc.
(T _D )S, and then provides this to the arithmetic unit _OP1 .

Therefore, the output PV(T _D )S is the set temperature signal
During the period below CH(T _D )S, the calculation unit OP ₁ calculates PV(RH) based on the output PV(T _D )S and the output PV(T _W )S of the wet bulb temperature sensor. After determining PV (RH) according to the formula, in order to give it to the control unit CTh, it is compared with the set humidity signal SP (RH) set by a potentiometer, etc., and proportional, integral, differential (hereinafter referred to as PID) ) etc. are performed by the control unit CT _h , and the control signal for the humidifier is
The humidifier is sent out as a CRS, and the humidifier operates accordingly to perform humidification and supply of heat energy by the humidifier.

On the other hand, due to the increase in PV (T _D ), the output PV
When (T _D )S increases and becomes equal to or greater than the value of the switching temperature signal CH (T _D )S, the comparator CP produces a comparison output;
The switch SW operates, and the switch for calculation section OP ₁ is activated.
In order to switch the SW output from the output PV(T _D )S to the set temperature signal SP(T _D )S, the output PV(T _D )
S becomes irrelevant to the calculation of PV(RH), and PV(RH) is calculated based on the set temperature signal SP(T _D )S and the output PV(T _W )S, and this result and the set humidity signal SP (RH)S, the status of the control signal _CRS is determined according to The system stops and PV (RH) is stably controlled.

In addition, the output PV(T _D )S and the set temperature signal SP
(T _D )S is also given to the control unit CT _t ,
Control unit CT _t has the same comparison and PID as control unit CT _h
The calculation sends a control signal CTS to the heater, which controls the operation of the heater.

In addition, for the purpose of separately determining and instructing PV (RH) faithfully, the output PV (T _D )S and
An arithmetic unit _OP2 to which PV(T _W )S is provided is provided, which also performs the arithmetic operation of equation (1) and sends out an instruction signal DMS to a digital humidity indicator or the like.

Therefore, when PV (T _D ) reaches CH (T _D ), the fixed set temperature signal SP (T _D )S and the output
PV(T _W )S and PV(RH) for control are required, and the influence of the increase in PV(T _D ) caused by the supply of thermal energy from the humidifier is blocked, resulting in stable and stable operation without thermal runaway. Highly accurate PV(T)
_D ) and PV (RH) are controlled.

In addition, if PV (T _D ) and wet bulb temperature T _W are in a high humidity state where they are almost the same, PV (T _D ) > CH (T _D )
The relationship is as follows, and the calculation section OP ₁ receives the set temperature signal SP.
(T _D )S is given, and the wet bulb temperature T _W >SP
(T _D ), so the calculation result PV (RH)
= 100%, and when the value of the set temperature signal SP (RH) S is smaller than this, the humidifier maintains the stopped state of operation, and while PV (T _D ) falls to SP (T _D ), This is a favorable condition in which dew condensation is unlikely to occur.

Note that the calculations in the calculation units OP ₁ and OP ₂ may be performed faithfully according to equation (1), but the value of PV (RH) corresponding to the dry bulb temperature T _D and the wet bulb temperature T _W is calculated in advance. If it is stored in the memory as a table and PV (RH) is obtained from this table, the configuration of the arithmetic circuit can be simplified compared to the calculation using equation (1).

However, each part shown in the figure may be replaced with the functions of a microcomputer mainly consisting of a microprocessor, memory, etc. In this case, a program may be set using the same steps as described above. etc., various modifications are possible.

In addition, when using a microcomputer etc.,
Compared to a method in which dry bulb temperature T _D and wet bulb temperature T _W are determined from SP (RH) by back calculation and then controlled, according to the present invention, by calculation of equation (1) or the above table, , SP (RH) can be set directly, simplifying programs and reducing memory capacity.

As is clear from the above explanation, according to the present invention, the temperature and humidity of a constant temperature and humidity chamber can be controlled stably and with high precision using a simple and inexpensive configuration without causing thermal runaway. Shows remarkable effects in wet tanks.

[Brief explanation of the drawing]

The figure is a block diagram showing an embodiment of the present invention. CP...Comparator, SW...Switcher, OP ₁ , OP ₂ ...
...Arithmetic unit, CT _t , CT _h ...Control unit.

Claims (1)

[Claims] 1. A dry bulb temperature sensor and a wet bulb temperature sensor are provided, and relative humidity is determined by calculation based on the outputs of both sensors, temperature is determined from the output of the dry bulb temperature sensor, and set temperature and In a constant temperature and humidity chamber that controls temperature and humidity by comparing with a set humidity, a switching temperature is set near the set temperature, and the dry bulb temperature sensor is used for the calculation when the temperature becomes equal to or higher than the switching temperature. A method for controlling a constant temperature and humidity chamber, characterized in that the output of the constant temperature and humidity chamber is switched to a signal indicating the set temperature. 2 Equipped with a dry bulb temperature sensor and a wet bulb temperature sensor, the relative humidity is determined by calculation based on the outputs of both sensors, the temperature is determined from the output of the dry bulb temperature sensor, and the temperature is compared with the set temperature and set humidity. In a constant temperature and humidity chamber that controls temperature and humidity, a switching temperature signal indicating a switching temperature set near the set temperature is compared with the output of the dry bulb temperature sensor, and the output is equal to or higher than the switching temperature signal. a comparator that sometimes generates a comparison output; a switch that switches from the output of the dry bulb temperature sensor to a set temperature signal indicating the set temperature according to the comparison output; and an output of the switch and an output of the wet bulb temperature sensor. 1. A control device for a constant temperature and humidity chamber, comprising a calculation section that calculates relative humidity based on the temperature and humidity.