JPH10104214A - Temperature controlling device for measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature controlling device which is excellent in overshoot or safety. SOLUTION: A reachable temperature predicting part 2 predicts a temperature which will be reached in an oven after an elapse of a fixed time when both heating and cooling are not carried out from a certain time, using the temperature detected by a temperature sensor, and data on the heat capacity of the oven. An optimum heat quantity-calculation part 4 calculates the quantity of heat for compensating for the difference between the reachable temperature predicted by the reachable temperature predicting part 2, and a target temperature. A heater's output voltage calculation part 6 calculates and outputs the heater's output voltage which is equivalent to the heat quantity calculated by the optimum heat quantity calculation part 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature controller for controlling the temperature of an oven of a measuring device such as a liquid chromatograph.

[0002]

2. Description of the Related Art Generally, as a temperature control device for a column oven of a high-performance liquid chromatograph, a heating output and a cooling output are determined by performing PID control by an analog circuit. The PID control is based on a difference between a detected temperature of an object such as an oven and a target temperature to be set, an integrated value thereof,
And its derivative multiplied by a coefficient to determine the output. In some cases, temperature control is performed using a microcomputer. Even in such a case, calculation is generally performed by digitally simulating the operation of an analog circuit.

[0003]

In the PID control, the temperature difference, the integral value, and the derivative value are simply multiplied by coefficients to determine the output, and the amount of heat required to reach the target temperature is calculated. is not. Therefore, depending on the setting of the coefficient, problems such as a large overshoot, a long time to reach stability, and poor stability even when stable are likely to occur. Setting coefficients to prevent these problems from occurring is not easy. An object of the present invention is to provide a temperature control device excellent in overshoot and stability by a method other than PID control.

[0004]

FIG. 1 is a schematic diagram showing an embodiment of the present invention. The temperature control device includes only a heating unit or a heating unit including a heating unit and a cooling unit, and adjusts the temperature of the oven of the measurement device, and includes a temperature sensor that detects at least the temperature in the oven.
Further, the provided ultimate temperature predicting unit 2 uses data of the temperature detected by the temperature sensor and the heat capacity of the oven,
Predict the temperature that the oven will reach after a certain time if neither heating nor cooling has taken place from a certain point in time.
The optimum calorific value calculating unit 4 calculates a calorific value for filling the difference between the predicted temperature reached by the reached temperature predicting unit 2 and the target temperature. The heat source output voltage calculation unit 6 calculates a heat source output voltage corresponding to the heat amount calculated by the optimum heat amount calculation unit 4 and outputs it to the heat source unit.

[0005] As a type of oven, an object such as a column installed in the oven is temperature-controlled from a heat source using air as a medium, and an object such as a column in the oven is formed of a metal block having good thermal conductivity. In some cases, the temperature is controlled by contacting the metal block with a heat source. In the former case, the temperature sensor is arranged in a space inside the oven without contacting the heat source, and in the latter case, it is usually provided in contact with the metal block. Therefore, the “temperature in the oven” in the present invention means the temperature of the air in the oven in the former case using air as a medium, and the temperature of the metal block in the latter case using a metal block.

[0006]

FIG. 2 shows an embodiment of the present invention, which shows a column oven for a high-performance liquid chromatograph and a temperature control device therefor. The oven container 10 is a container having a certain heat retaining performance, and includes a heater 12 for housing a column and generating heat. Reference numeral 14 denotes the heat generated from the heater 12
This is a radiating fin that radiates heat into the inside. A power supply device 16 is provided outside the container 10 to supply power to the heater 12. Heater 12, radiation fin 14, and power supply device 1
Reference numeral 6 denotes a heat source unit.

A temperature sensor 18 for detecting the temperature inside the oven is arranged in the container 10, and a temperature sensor 20 for detecting the outside air temperature around the oven is provided outside the container 10. A microcomputer 22 is provided for taking in temperature detection signals from the temperature sensors 18 and 20 each time and controlling power supply from the power supply device 16 to the heater 12 so that the temperature in the oven becomes the target temperature. The microcomputer 22 implements the functions of the attained temperature estimator 2, the optimum calorie calculator 4, and the heater output voltage calculator 6 shown in FIG.

Next, the operation of this embodiment will be described with reference to FIGS. When the temperature control operation is started, the microcomputer 22 detects the temperature T ₂ in the oven from the sensor 18.
(Step S1). When the temperature is detected for the second time or later, the differential value of the oven temperature (dT ₂ / d
t) is calculated (step S2). In addition, the temperature sensor 2
0 taking outside air temperature T ₃ from (step S3).

Here, in addition to T ₂ and T ₃ , the radiation fins 14
If the temperature of the heater 12 is set to T ₁ (not detected), the heat capacity of the radiation fins 14 is set to C ₁ , and the heat capacity of the air in the oven is set to C ₂ , the power supply to the heater 12 is stopped at a certain point in time. T ₂ changes depending on the amount of excess heat (or insufficient heat) in the fins 14, and is near T ₂ ′ ≒ T ₂ + (T ₁ −T ₂ ) × C ₁ / (C ₁ + C ₂ ) (1) It is expected that equilibrium will be reached at a temperature of. However, here we do not consider the heat that escapes from the oven.
Here, (T ₁ −T ₂ ) is not directly measured, but the rate of change of the temperature in the oven with respect to time (dT ₂ / dt) is proportional to the amount of heat flowing from the fins 14 into the oven. Temperature difference from internal temperature (= T ₁ −
Since the relationship of being proportional to T ₂ ) holds, the following processing can be performed with (T ₁ −T ₂ ) ≒ A × (dT ₂ / dt) (1a). The coefficient A at this time can be obtained by theoretical calculation or actual measurement.
In this way, the oven reaching temperature T ₂ ′ is predicted by calculation (step S4).

The amount of heat Q required to raise the oven temperature until the oven temperature T ₂ ′ matches the target temperature Tset is estimated by calculation (step S5). Q is _{= (Tset-T 2 ')} × (C 1 + C 2) (2).

On the other hand, the amount of heat ΔQ ₂₃ escaping from the oven per unit time is calculated (step S6). Delta] Q ₂₃ can be obtained by (T ₂ -T ₃₎ in a generally _{proportional, ΔQ 23 = (T 2 -T} 3) × A 23 (3). Here, the proportional coefficient A ₂₃ is
Generally, it can be theoretically calculated from the material and structure of the oven, or can be obtained by actual measurement.

Next, an appropriate time length Δt (depending on the heater capacity, the easiness of the temperature change in the oven, etc.) is set, and the optimum heat quantity Q (t) taking into account ΔQ ₂₃ is calculated (step). S7). Q (t) is as follows: Q (t) = Q + ΔQ ₂₃ × Δt (4) The amount of generated heat Q (t) is proportional to the heater voltage, and the proportional coefficient can be easily obtained by theoretical calculation or actual measurement. For example, the heater output voltage corresponding to Q (t) is calculated by inputting the heater characteristics and the heat capacity of the oven (steps S8 and S9). Based on the output voltage, the amount of power supply from the power supply device 16 to the heater 12 is controlled (step S10). This operation is repeated at regular intervals.

In the operation of FIG. 3, although the amount of heat escaping from the oven is not considered in step S5, the necessary amount of heat Q may be estimated in S5 in consideration of the amount of heat. Although the temperature of the radiation fin 14 is not detected in the embodiment, a sensor for detecting the temperature T ₁ of the radiation fin 14 is further provided, and without using the rate of change of the oven temperature T ₂ ,
T ₂ ′ may be calculated directly using equation (1). The oven may be further provided with a cooling device.
In that case, the term of the amount of heat absorbed by the cooling device is added to the right side of equation (4).

If the amount of heat escaping from the oven cannot be accurately determined due to the insulation properties of the oven, the temperature is actually adjusted, and the amount of heat escaping from the result is calculated. Correction of ΔQ ₂₃ in equation (3) allows accurate temperature control. When a fan whose rotation speed is variable is provided in the oven, the proportionality coefficient A in the equation (1a) can be made a function of the rotation speed of the fan. The function can be obtained by theoretical calculation or actual measurement.

In the embodiment, the temperature of the air inside the oven is detected as the temperature inside the oven. However, in the case of an oven using a metal block, the temperature of the metal block is detected instead of the temperature of the air inside the oven. 3 may be performed in the same manner as in FIG.

In the embodiment, a sensor for detecting the outside air temperature T ₃ is provided. However, the temperature can be controlled without detecting the outside air temperature T ₃ . The operation in that case may be performed as follows. (1) Instead of detecting the outside air temperature, the outside air temperature is regarded as a specific value, and the amount of heat escaping outside is estimated. (2) Actual temperature control. (3) The amount of heat actually escaping to the outside is obtained from the result of temperature control. (4) Repeat processes (2) and (3).

[0017]

The present invention uses the data of the temperature detected by the temperature sensor and the heat capacity of the oven, and predicts the arrival that the inside of the oven will reach after a certain period of time if neither heating nor cooling is performed from a certain point in time. Calculate the amount of heat to fill the difference between the temperature and the target temperature, calculate and output the heat source output voltage corresponding to the amount of heat, and adjust the oven temperature, so that the target temperature is reached in a short time, High stability can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically illustrating the present invention.

FIG. 2 is a schematic sectional view showing one embodiment.

FIG. 3 is a flowchart illustrating the operation of one embodiment.

[Explanation of symbols]

 2 Ultimate temperature prediction unit 4 Optimum calorific value calculation unit 6 Heater output voltage calculation unit 12 Heater 14 Radiation fins 18, 20 Temperature sensor 22 Microcomputer

Claims (1)

[Claims] Claims 1. A heating section only or includes a heating section and a cooling section,
A heat source unit for adjusting the temperature of the oven of the measuring device, a temperature sensor for detecting at least the temperature in the oven, and using the data of the temperature detected by the temperature sensor and the heat capacity of the oven, neither heating nor cooling is performed from a certain point in time. A temperature predicting unit that predicts a temperature that the inside of the oven will reach after a certain period of time, and an optimum calorific value calculation that calculates a calorific value for filling a difference between the predicted temperature reached by the reached temperature predicting unit and the target temperature. And a heat source output voltage calculation unit that calculates a heat source output voltage corresponding to the heat amount calculated by the optimum heat amount calculation unit and outputs the heat source output voltage to the heat source unit.