JPH03118619A - Temperature control method for thermostatic chamber - Google Patents

Abstract

PURPOSE:To attain the optimum control having a short rise time by obtaining the difference between an ambient temperature and a desired set temperature and obtaining a temperature control constant optimum to the difference temperature based on the value stored previously in a temperature control program. CONSTITUTION:The ON/OFF control of a thermostatic heater is started when a heater is turned on. Then the temperature rising slope of a thermostatic chamber is measured. Then an ambient temperature is obtained from the slope obtained based on the slope of a temperature rising curve which is previously stored in a temperature control program. Then the difference is obtained between a set temperature and the ambient temperature, and a temperature control constant optimum to the obtained difference temperature is obtained based on the slope of the temperature rising curve stored previously in the temperature control program. The temperature control constant is set to a microcomputer, etc., and therefore changed. Then the proportional plus integral control is started when a temperature deviation (t1-t2) is set smaller than a minute temperature difference td. Thus it is possible to attain the optimum control which is corresponding to all conditions and has a short rise time.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for controlling the temperature of a constant temperature bath used, for example, in a liquid chromatograph.

<Conventional technology> If the temperature of a constant temperature chamber used in a liquid chromatograph is controlled only by proportional control (P control), an output is produced only when there is a difference between the set temperature and the detected temperature. A phenomenon occurs in which deviation occurs and the set temperature is never reached. For this reason, proportional-integral control (PI sub-control) is performed that outputs a value obtained by adding an integral value to compensate for the temperature deviation. When performing this proportional-integral control, the amount of heat given to the heater is determined by It is determined by a time-dependent temperature control constant.In order to reach the desired set temperature as soon as possible and stabilize it, it is necessary to supply the optimum amount of heat to the thermostatic oven at the time of startup of the thermostatic oven temperature.

On the other hand, FIG. 2 is a schematic explanatory diagram showing a conventional temperature control method for a constant temperature bath. In the figure, the horizontal axis is time (mi
n, ), and the vertical axis is the measured temperature (.

C) is shown. In this figure, at the start of control (T1
), the measured temperature shows t2, and then the temperature is controlled and finally reaches the set temperature t2. That is, the temperature difference (t
If lt = 2) > minute temperature difference td, the integral control operation is stopped and on/off control is performed so that the heater is continuously energized.In this way, the measured temperature becomes (tl ta
), temperature difference (tl t2) < minute temperature difference td
If , the integral operation is started and proportional-integral control is started. Therefore, the temperature t2 at the start of control is the set temperature t
, the temperature difference (tl
When t2)=minimal temperature difference (t, i), a state similar to proportional-integral control is reached.

However, the optimal amount of heat required at the start-up of the thermostatic chamber temperature is a function of the difference between the set temperature and the ambient temperature (for example,
The optimal amount of heat required to stabilize the desired set temperature of 90°C is significantly different when the ambient temperature is 5°C and when the ambient temperature is 55°C.)

Because of this, the amount of heat that is optimal under certain conditions may be too large or too small under other conditions, which has an adverse effect on the temperature rise time of the thermostatic chamber. That is, if the amount of heat is too large, temperature overshoot occurs, and if it is too small, temperature undershoot occurs, and it takes a very long time to stabilize the set temperature.

The present invention has been made in view of the drawbacks of the conventional example, and its object is to shorten the rise time of the thermostatic chamber temperature so that it can be stabilized at the set temperature more quickly. The objective is to provide an optimal temperature control method.

Means for Solving the Problems> A feature of the present invention that solves the problems described above is that in a method for controlling the temperature of a constant temperature bath used in a liquid chromatograph, temperature rise curves at various ambient temperatures are determined in advance. The slope and the optimum temperature control constant for various temperature differences are determined and stored in the temperature control program, the slope of the temperature rise curve of the thermostatic chamber is measured, and the slope is stored in the temperature control program from this measured value. The ambient temperature is determined based on the slope of the temperature rise curve, the temperature difference is determined from the ambient temperature and the desired set temperature, and the optimum temperature control constant for the temperature difference is determined from the value stored in the temperature control glodarum. It lies in seeking from.

Function> The present invention functions as follows. That is, the slope of the temperature rise curve at various ambient temperatures and the optimum temperature control constant for various hot water differences are determined in advance through experiments, etc., and stored in the temperature control program, and the slope of the temperature rise curve of the thermostatic oven is measured. From this measured value, the ambient temperature is determined based on the slope of the temperature rise curve stored in the temperature control program. A temperature difference is determined from the ambient temperature thus determined and the desired set temperature, and a temperature control constant optimal for the temperature difference is determined from values stored in the temperature control program. By setting the temperature control constant obtained in this manner in a microcomputer or the like, the temperature control constant is changed.

<Example> Hereinafter, the present invention will be described in detail using the drawings. 1st
The figure shows flowchart 1 showing the temperature control method according to the present invention.
6 Below, the temperature control method according to the present invention will be explained in detail using this figure.

First, the slope of the temperature rise curve of the constant temperature chamber at various ambient temperatures and the optimal temperature control constant at various temperature differences are determined through experiments, etc., and these curves and values are stored in advance in the temperature control program. Thereafter, as shown in step 1 of FIG. 1, the heater of the thermostatic oven is turned on. By turning on the heater, on/off control of the constant temperature oven heater is started as shown in step 2 of FIG.

Thereafter, as shown in step 3 of FIG. 1, the slope of the temperature rise curve of the thermostatic chamber is measured.

Thereafter, based on the slope of the temperature rise curve previously stored in the temperature control glodarum, the ambient temperature is determined as shown in step 4 of FIG. 1 from the slope determined in the third step. That is, the temperature rise in the constant temperature oven is the amount of heat that is obtained by subtracting the amount of heat escaping from the constant temperature oven from the amount of heat supplied from the heater. Therefore, if the amount of heat supplied from the heater is constant,
The degree of temperature rise in the thermostatic oven (the slope of the temperature rise curve) changes depending on the amount of heat escaping from the thermostatic oven6.
The amount of heat escaping from the thermostatic oven is proportional to the ambient temperature.

Therefore, the degree of temperature rise in the thermostatic oven (the slope of the temperature rise curve) can be regarded as a function of the ambient temperature.

For this reason, the temperature rise curve (more specifically, the slope of the temperature rise curve) of the constant temperature oven when the heater is continuously energized corresponds to the ambient temperature. Therefore, the ambient temperature can be determined from the slope of the temperature rise curve.

Thereafter, as shown by Stella 15 in FIG. 1, the temperature difference is determined from the set temperature and the ambient temperature.

Thereafter, the optimum temperature control constant for the temperature difference found in step 5 of FIG. 1 is found from the slope of the temperature rise curve previously stored in the temperature control program.

Thereafter, the temperature control constant determined in step 6 of FIG. 1 is set in the microcomputer (), thereby changing the temperature control constant as shown in step 7 of FIG.

Thereafter, as shown in step 8 of FIG.
+ tz)<minimal temperature difference (1, 1), proportional-integral control is started.

Note that the present invention is not limited to the above-described embodiments, and can be modified in various ways.

<Effects of the Invention> According to the embodiments of the present invention as described in detail above, in a method for controlling the temperature of a constant temperature bath used in a liquid chromatograph, etc., the slope of the temperature rise curve at various ambient temperatures and the The optimum temperature control constants for various temperature differences are determined and stored in the temperature control program, the slope of the temperature rise curve of the thermostatic chamber is measured, and the measured value is stored in the temperature control program. Determine the ambient temperature based on the slope of the temperature rise curve, determine the temperature difference from the ambient temperature and the desired set temperature, and determine the temperature control constant optimal for the temperature difference from the values stored in the temperature control program in advance. It was configured as desired. This advantage has the advantage of realizing optimal control with a short rise time that corresponds to all conditions such as ambient temperature and set temperature. Another advantage is that the manufacturing cost of the thermostatic chamber is low because the ambient temperature can be estimated without the need for a special sensor to measure the ambient temperature.

[Brief explanation of drawings]

FIG. 1 is a flowchart for explaining the temperature control method according to the present invention, and FIG. 2 is a schematic explanatory diagram showing a conventional temperature control method for a constant temperature oven. tl...set temperature, t2...indicated temperature

Claims (1)

[Claims] In a method of controlling the temperature of a constant temperature bath used in liquid chromatographs, etc., the slope of the temperature rise curve at various ambient temperatures and the optimal temperature control constant at various temperature differences are determined in advance and stored in the temperature control program. Then, measure the slope of the temperature rise curve of the thermostatic chamber, calculate the ambient temperature from this measured value based on the slope of the temperature rise curve stored in the temperature control program, and compare the ambient temperature with the desired temperature. A method for controlling a constant temperature oven, characterized in that a temperature difference is determined from a set temperature, and a temperature control constant optimal for the temperature difference is determined from a value stored in the temperature control program.