JP2006194706A - Temperature control device in analyzer - Google Patents

Abstract

【Task】
A high-resolution A / D converter is not required and temperature control can be performed with high accuracy.
[Solution]
The heating unit 4 for heating the temperature control block 2 in the analyzer, the temperature measurement means 8 and 10 for measuring the temperature of the temperature control block 2, and the heating unit so that the temperature measured by the temperature measurement unit 10 becomes a predetermined temperature. 4 is provided with a temperature control unit that controls the temperature control unit 4, the temperature control unit 14 that can change the set temperature, and an A / D-converted output signal of the temperature measurement means 10, and the acquired signal. The set temperature control unit 20 that sets the set temperature of the temperature setting unit 14 so that the temperature corresponding to the temperature approaches a predetermined temperature, the output signal corresponding to the measured temperature of the temperature measuring unit 10, and the set temperature of the temperature setting unit 14 A comparison circuit 12 that compares the corresponding signals and controls the energization of the heating unit 4 according to the difference is provided.
[Selection] Figure 1

Description

  The present invention relates to a temperature control device in an analyzer such as a high performance liquid chromatograph, for example, various detectors (absorbance detector, fluorescence detector, differential refractometer detector, etc.), column oven or injector (hereinafter referred to as “high performance liquid chromatograph”). These are collectively referred to as a detector or the like.) This relates to a temperature control device for heating or cooling the temperature of the detector to a predetermined temperature.

  For example, in a high performance liquid chromatograph, as a method for realizing a temperature adjustment function (temperature adjustment is referred to as “temperature adjustment”) for adjusting the temperature of a detector or the like to a predetermined temperature, a method utilizing the heat loss of a transistor and a Peltier device are used. A method using an element is used. In the former case, the temperature of the temperature-controlled part is measured with a thermistor, and if the measured temperature is lower than the set temperature, the collector current is supplied to the transistor and heated by the heat loss. If the measured temperature is higher than the set temperature, the collector current is stopped. The temperature is controlled by the method of natural cooling. The latter case is basically similar, and energization to the Peltier element is controlled according to the difference between the measured temperature and the set temperature.

  At that time, the function of determining whether the collector current should be supplied or stopped depending on the measured temperature, or how the Peltier element is energized includes a hardware (H / W) method and a software (S / W) method. There is.

  In the H / W method, a conversion voltage corresponding to the set temperature is fixed, and the voltage converted from the measured temperature is compared with an operational amplifier (op amp), and the energization of the heating transistor or Peltier element is feedback controlled.

In the S / W method, a CPU (central processing unit) that reads the measured temperature outputs a signal that controls energization of the heating transistor or the Peltier element so that the measured temperature approaches the set temperature.
Conventionally, the H / W method is often used.

  In recent years, since a high-resolution A / D converter (conversion from an analog signal to a digital signal) such as a delta-sigma method has come out, the S / W control method has become mainstream. For example, since a ΔΣ A / D converter has an effective resolution of about 20 bits, if this is used, control in units of 0.01 ° C. is sufficiently possible.

  Some CPUs with built-in A / D converters have appeared in recent years, but the resolution is 8 to 10 bits, and this is used in the S / W control method to set the temperature of the detector to a predetermined value. Low resolution to adjust to temperature.

For this reason, the S / W control method requires a high-resolution A / D converter dedicated to temperature measurement, which increases costs and increases board space.
On the other hand, in the conventional H / W method, since the two voltages are directly compared to perform feedback control control, the temperature can be controlled with high accuracy. There was variation in (absolute value).

  An object of the present invention is to eliminate the need for a high-resolution A / D converter and to enable temperature control with high accuracy.

  The temperature control apparatus of the present invention includes a heating unit that heats the temperature control block in the analyzer, a temperature measurement unit that measures the temperature of the temperature control block, and a temperature measured by the temperature measurement unit so that the temperature is a predetermined temperature. And a temperature control unit for controlling the heating unit. The temperature adjustment unit takes in an output signal from the temperature setting unit that can change the set temperature and the temperature measuring means by A / D conversion, and the temperature corresponding to the taken-in signal approaches the predetermined temperature. The set temperature control unit for setting the set temperature of the temperature setting unit, the output signal corresponding to the measured temperature of the temperature measuring means and the signal corresponding to the set temperature of the temperature setting unit are compared, and the difference Accordingly, a comparison circuit for controlling energization of the heating unit is provided.

  In the present invention, the use of the high-resolution A / D converter is not excluded by using the feedback temperature control by the H / W method and the temperature setting by the S / W method, but the low-resolution A / D converter is not excluded. Even if this is used, high-resolution temperature control can be realized. Therefore, in a preferred embodiment, the A / D converter for A / D converting the output signal of the temperature measuring means is an A / D converter having a lower resolution than that required by the temperature control device.

  In a more preferred embodiment, the set temperature control unit is a CPU. In that case, in a more preferred form, an A / D converter for A / D converting the output signal of the temperature measuring means is built in the CPU.

For example, in order to adjust the temperature range of 10 to 70 ° C. in units of 0.1 ° C., (70−10) /0.1=600≦2 ¹⁰ , so 10-bit resolution is sufficient. However, in order to adjust the temperature range in units of 0.01 ° C., (70−10) /0.01=6000≦2 ^13, and 13-bit resolution is required.

A commercially available CPU has a 10-bit resolution of the built-in A / D converter, so it can be read in units of 0.1 ° C, but cannot be read in units of 0.01 ° C. If only control is performed, control in units of 0.01 ° C. is impossible.
However, for example, the temperature that the user wants to confirm in the liquid chromatograph is sufficient in units of 0.1 ° C., and even if it can be read in units of 0.01 ° C., there is no point. On the other hand, the temperature control performance required for the analysis may be slightly different in absolute temperature value, but the temperature accuracy when it is controlled to constant requires a resolution of 0.01 ° C. or higher.

  Therefore, in the present invention, for example, the temperature is read at a 10-bit resolution level, the voltage corresponding to the set temperature is determined by the S / W method, and then the control is switched to the H / W method. As a result, the variation of the components is absorbed, the set temperature is set to about 0.1 ° C., and the control is performed with high accuracy by the H / W method so as to follow the determined value.

In a further preferred form of the present invention, a display unit is further provided, and the set temperature control unit displays an output signal of the temperature measuring means captured by A / D conversion on the display unit.
An example of an analyzer to which the present invention is applied is a high performance liquid chromatograph. In this case, the temperature control device controls the temperature of at least one of the detector, the column oven, and the injector.

The temperature control device of the present invention enables high-resolution temperature control even when a low-resolution A / D converter is used by using feedback temperature control by H / W method and temperature setting by S / W method in combination. become.
As a result, a built-in CPU can be used as an A / D converter for A / D converting the output signal of the temperature measuring means. In this case, a high-resolution A / D converter and its peripheral parts are unnecessary, which is advantageous in terms of cost and space.

Further, since the program for reading the external A / D converter is more complicated than the program for reading the CPU built-in A / D converter, the program development time can be shortened.
Furthermore, if a display unit is provided so that the output signal of the temperature measuring means captured by A / D conversion is displayed on the display unit, the measured temperature can be confirmed by the user with the resolution of the A / D converter. Therefore, user convenience is improved.

FIG. 1 is a circuit block diagram schematically showing an embodiment.
Reference numeral 2 denotes a temperature control block in the analyzer. The temperature control block 2 is, for example, a temperature control block of a detector, a column oven, or an injector when a high performance liquid chromatograph is taken up as an analyzer. However, the present invention is not limited to this, and any other analytical apparatus can be applied to any temperature control block for heating or cooling of a portion requiring temperature control.

  Reference numeral 4 denotes a heating transistor as a heating unit for heating the temperature control block 2, which is composed of an NPN transistor, whose collector is connected to the power supply terminal (24V), and whose emitter is connected to the ground terminal via the current detection resistor 6. ing.

  The temperature control block 2 is provided with a thermistor 8 as a temperature measuring element in order to detect the temperature. The thermistor 8 is connected to the temperature measuring unit 10, and the temperature detected by the thermistor 8 is converted into a corresponding voltage by the temperature measuring unit 10. The thermistor 8 and the temperature measuring unit 10 constitute temperature measuring means for measuring the temperature of the temperature control block 2.

  Reference numeral 12 denotes an operational amplifier that constitutes a comparison circuit. An output voltage corresponding to the measured temperature of the temperature measuring unit 10 is applied to the inverting input terminal, and the non-inverting input terminal corresponds to the set temperature of the temperature setting unit 14. An output voltage is applied. The output terminal of the comparison circuit 12 is connected to the base of the heating transistor 4. The comparison circuit 12 compares the output voltage of the temperature measurement unit 10 with the output voltage of the temperature setting unit 14 and performs on / off control of energization of the heating transistor 4 according to the difference.

  The temperature setting unit 14 can change the set temperature, and inputs a pulse width modulated (PWM) signal to convert it into a voltage. Specifically, for example, as shown in FIG. A resistor 16 for guiding the signal to the non-inverting input terminal of the comparison circuit 12 and a capacitor connected between the non-inverting input terminal and the ground terminal are provided.

Returning to FIG. 1, reference numeral 20 denotes a CPU as a set temperature control unit, which uses, for example, a built-in 10-bit A / D converter. The CPU 20 is set with a temperature control temperature for adjusting the temperature control block 2 to a predetermined temperature, for example, 40 ° C. The CPU 20 captures the output signal of the temperature measurement unit 10 by A / D conversion via a built-in A / D converter, and applies pulse width modulation to the temperature setting unit 14 so that the captured temperature approaches a predetermined temperature control temperature. The set temperature of the temperature setting unit 14 is set by outputting the signal. In the temperature setting unit 14, the voltage of the temperature setting unit 14 is set in accordance with the duty of the pulse signal subjected to pulse width modulation output from the CPU 20 (ratio of on time in one cycle of the pulse signal).
A display unit 22 such as a liquid crystal display element is connected to the CPU 20, and the CPU 20 displays the temperature acquired by A / D converting the output signal of the temperature measuring unit 10.

  When the output voltage of the temperature setting unit 14 input to the non-inverting input terminal is equal to or higher than the output voltage of the temperature measuring unit 10 input to the inverting input terminal of the comparison circuit 12, the output of the comparison circuit 12 Becomes a high level signal, whereby the heating transistor 4 is turned on and energized to generate heat, and the temperature of the temperature control block 2 rises. On the other hand, when the output voltage of the temperature setting unit 14 input to the non-inverting input terminal is lower than the output voltage of the temperature measuring unit 10 input to the inverting input terminal of the comparison circuit 12, the output of the comparison circuit 12 is As a result, the heating transistor 4 is turned off, the energization is stopped and the heat generation is stopped, and the temperature of the temperature control block 2 is lowered by heat radiation (natural cooling).

  The circuit block diagram of FIG. 1 is simplified for easy understanding, but actually, circuit elements are further provided. For example, a feedback resistor is connected to the comparison circuit 12, a pre-stage transistor by Darlington connection is connected to the heating transistor 4, and a thermostat for temperature runaway protection is provided between the heating transistor 4 and the power supply terminal or between the ground terminal. An operational amplifier for generating an appropriate voltage is connected to the temperature measurement unit 10.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG.
Here, it is assumed that the temperature control set temperature is 40 ° C.
(1) S / W control by setting 40 ° C. is started (step S1). That is, a pulse signal having a predetermined duty for setting 40 ° C. is output from the CPU 20 to the temperature setting unit 14, the set temperature of the temperature setting unit 14 is set, and the temperature measurement unit 10 detects the thermistor 8. Measure the temperature.

  (2) If the temperature measured by the temperature measuring unit 10 is continuously within a range of (40−0.1) ° C. to (40 + 0.1) ° C. for a certain time (for example, 5 minutes) or longer (step S2), the CPU 20 The duty of the pulse signal sent to the temperature setting unit 14 is fixed and the set voltage is made constant (step S3). That is, the setting voltage of the non-inverting input terminal of the comparison circuit 12 is fixed, and the process proceeds to H / W control by the comparison circuit 12.

(3) If the condition that the temperature measured by the temperature measurement unit 10 is continuously within a range of (40−0.1) ° C. to (40 + 0.1) ° C. for a certain time or longer is not satisfied (step S2), a timeout occurs It is checked whether (predetermined time has elapsed) (step S4). The predetermined time for timeout may be set to about twice the fixed time in step S2. Therefore, in this example, the predetermined time for determining the timeout is 10 minutes.
If not timed out, the process returns to step S2 via steps S5 and S6.

  (4) In step S5, if the measured temperature is less than 40 ° C., it is necessary to increase the temperature. Therefore, the duty of the pulse signal sent from the CPU 20 to the temperature setting unit 14 is increased to increase the set voltage of the temperature setting unit 14. (Step S7).

  (5) In step S6, if the measured temperature is higher than 40 ° C., it is necessary to lower the temperature. Therefore, the duty of the pulse signal sent from the CPU 20 to the temperature setting unit 14 is lowered to lower the set voltage of the temperature setting unit 14. (Step S8).

  The program for adjusting the set temperature in steps S7 and S8 preferably incorporates PID control. PID control is a well-known technique, and performs feedback control including a proportional component (P), an integral component (I), and a differential component (D) with respect to a deviation between a target value and a current value. P control including P, P control including a proportional component and an integral component, and PD control including a proportional component and a differential component are also included.

  The loop which returns to S2 through steps S2 to S6 is S / W control for determining the set temperature of the temperature setting unit 14, and the measured temperature continues for a predetermined time or more (40− If it falls within the range of 0.1) ° C. to (40 + 0.1) ° C., the duty of the pulse signal sent from the CPU 20 to the temperature setting unit 14 is fixed to the value at that time, and the S / W in this loop If a predetermined time elapses during the control operation and a time-out occurs, the duty of the pulse signal sent from the CPU 20 to the temperature setting unit 14 is fixed to the value at that time. When the S / W control is thus completed and the set voltage of the temperature setting unit 14 is determined, the control circuit 12 shifts to H / W control.

  In the H / W control by the comparison circuit 12, since the set voltage of the temperature setting unit 14 is fixed, the voltage corresponding to the measured temperature obtained by the temperature measuring unit 10 is the same as the set voltage of the temperature setting unit 14. Feedback is applied by the comparison circuit 12 so that the collector current of the heating transistor 4 is optimally controlled.

  The temperature measurement unit 10 is always monitored by the CPU 20 with the resolution of the A / D converter built in the CPU 20, in this case, 10-bit resolution, and can be displayed to the user by the display unit 22.

  Although the case where a heating transistor is used as the heating portion is shown in the embodiment, temperature control can be similarly performed when a Peltier element is used. In addition, the Peltier element can be forcibly cooled not only by heating but also by changing the energization direction.

  The temperature control device of the present invention can be used for heating or cooling a temperature-controlled portion in various analyzers including a high-performance liquid chromatograph to a predetermined temperature.

It is a block circuit diagram which shows one Example. It is a circuit diagram which shows an example of the temperature setting part in the Example. It is a flowchart figure which shows the operation | movement of the Example.

Explanation of symbols

2 Temperature control block 4 Heating transistor 6 Current detection resistor 8 Thermistor 10 Temperature measurement unit 12 Comparison circuit 14 Temperature setting unit 20 CPU
22 Display section

Claims (6)

A heating unit that heats the temperature control block in the analyzer, a temperature measurement unit that measures the temperature of the temperature control block, and a temperature that controls the heating unit so that the temperature measured by the temperature measurement unit becomes a predetermined temperature. In the temperature control device provided with the adjustment unit,
The temperature control unit is a temperature setting unit capable of changing a set temperature, and
An A / D converted output signal of the temperature measuring means, and a set temperature control unit that sets a set temperature of the temperature setting unit so that a temperature corresponding to the acquired signal approaches the predetermined temperature;
A comparison circuit that compares an output signal corresponding to the measured temperature of the temperature measuring means and a signal corresponding to the set temperature of the temperature setting unit, and controls energization of the heating unit according to the difference; A temperature control device characterized by. 2. The temperature control device according to claim 1, wherein the A / D converter for A / D converting the output signal of the temperature measuring means is an A / D converter having a resolution lower than that required by the temperature control device. The temperature control device according to claim 1, wherein the set temperature control unit is a CPU. The temperature control apparatus according to claim 3, wherein an A / D converter for A / D converting an output signal of the temperature measuring means is built in the CPU. 5. The temperature control device according to claim 1, further comprising a display unit, wherein the set temperature control unit displays an output signal of the temperature measurement unit captured by A / D conversion on the display unit. 6. The temperature according to claim 1, wherein the analysis device is a high performance liquid chromatograph, and the temperature control device controls the temperature of at least one of the detector, the column oven, and the injector. Control device.

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