JP4207758B2 - Temperature controller for analyzer - Google Patents

Description

  The present invention relates to a temperature controller for an analyzer used in an analyzer that requires temperature control of a sample, such as an ultraviolet-visible spectrophotometer and a fluorescence spectrophotometer.

  In the ultraviolet-visible spectrophotometer and the fluorescence spectrophotometer, an electronic cold cell holder using a Peltier element is used to control the temperature of the sample with high accuracy (see Patent Document 1). The temperature control of such an electronic cold cell holder is performed as follows. That is, the temperature of the cell holder heated or cooled by the Peltier element is monitored in real time by a temperature sensor provided in close contact with the cell holder. Based on the error between the detected temperature and the target temperature, the control device controls the on / off time of the relay built in the switching power supply prepared for the Peltier element, and thereby supplies the current to the Peltier element. Adjust. As a result, the temperature of the cell holder finally reaches the target temperature and becomes stable.

  However, in such a conventional temperature control method, when the temperature at the lower end or the upper end of the set temperature range such as 0 ° C. or 100 ° C. is set as the target temperature, overshoot or ringing near the target temperature occurs. It tends to grow. For example, FIG. 2 is a schematic graph showing a temperature change state when the temperature is rapidly raised from the initial temperature T0 to the target temperature Tj by the conventional temperature control method. As shown in this graph, an overshoot in which the actual temperature greatly exceeds the target temperature Tj and ringing up and down across the target temperature Tj occur. The main reasons for such overshoot and ringing are as follows.

(1) Since the temperature is abruptly changed until it approaches the target temperature to some extent, even if the control algorithm is switched so as to gradually approach the target temperature from this state, the temperature change does not become gradual immediately. . In such a situation, it becomes difficult to control the on / off time of the relay, and the error tends to be larger than the intended temperature change.
(2) In the vicinity of the target temperature, it is necessary to frequently switch the polarity of the current supplied to the Peltier element. However, since the control dead time occurs at the time of polarity switching, it is difficult to obtain temperature stability.

  When such overshoot or ringing occurs, the sample deviates from the set temperature range. Therefore, for example, when measurement is performed at regular time intervals during the period from the temperature rising or falling process until the temperature is kept constant, the temperature is different from the desired temperature while overshooting or ringing occurs. Measurement is performed at temperature, and the accuracy of the measurement is impaired. In addition, when it is desired to perform measurement in a state where the temperature is stable after the temperature change, it takes time until the temperature stabilizes to the target temperature, which prolongs the analysis time and causes a decrease in analysis efficiency. Furthermore, for example, when the sample is a biological sample, if the temperature exceeds the set temperature range, denaturation may occur, a reaction different from the original intended reaction may occur, or it may proceed slowly slowly. There is a risk that the reaction will suddenly proceed, and not only the accuracy of the measurement is impaired, but in the worst case, the measurement result becomes meaningless.

JP 2003-121344 A (paragraphs 0016 and 0017)

  The present invention has been made in view of the above-mentioned problems, and its main purpose is to prevent the temperature change from being exceeded even when an extreme temperature change such as the upper limit end and the lower limit end of the set temperature range is performed. An object of the present invention is to provide a temperature control device for an analyzer that can quickly converge to a target temperature while suppressing chute and ringing.

The present invention made to solve the above problems is a temperature control apparatus for heating and cooling a sample to be analyzed through a temperature control object in an analysis apparatus.
a) heating / cooling means of N (N is an integer of 2 or more) channel mounted on the temperature control object;
b) N-channel temperature detecting means for detecting the temperature of the temperature control object in the vicinity of the respective mounting positions of the N-channel heating / cooling means;
c) driving means for supplying driving power to the heating / cooling means independently according to the control amount given for each channel;
d) processing means for weighting the control amount given to the driving means for each channel according to the difference between each detected temperature by the temperature detecting means of the N channel and the target temperature;
It is characterized by having.

  Here, various heating / cooling means can be used, and a Peltier element widely used for an analyzer can be used.

  In the temperature control apparatus according to the present invention, when the processing means receives N detected temperatures by the temperature detecting means of the N channel at a certain time, according to the difference between the N detected temperatures and the target temperature, Decide the weighting coefficient for each channel so that the channel with the smaller temperature difference has a lower weight, and immediately update the control amount for each channel by multiplying the control amount given to each channel by the weighting coefficient. . The drive means receives the updated control amount and increases or decreases the drive power supplied to the heating / cooling means. That is, the drive power is reduced for the channel whose weighting coefficient is changed to a small value, and the drive power is increased for the channel whose weighting coefficient is changed greatly. As a result, the channel that has a large difference between the target temperature and the actual temperature has a relatively large temperature change that fills the difference, and conversely, the channel has a small difference between the target temperature and the actual temperature. The temperature change that fills becomes relatively gradual. In this way, the heating / cooling means of each channel applies heat to the temperature control object independently and in a balanced manner according to the temperature non-uniformity due to the temperature control object part. As a result, the temperature of the temperature control object does not cause excessive overshoot or ringing, and quickly converges to the target temperature.

  In the temperature control device for an analyzer according to the present invention, when the difference between the target temperature and the actual temperature is large, it is not necessary to perform the weighting as described above, but rather to give or take away as much heat as possible. It is preferable to do. Therefore, as a preferred aspect of the present invention, the processing unit does not perform weighting processing of the control amount for each channel when the difference between the temperature detected by the temperature detecting unit and the target temperature exceeds a predetermined value. The processing may be executed when the value is equal to or less than the predetermined value.

  According to this configuration, when the difference between the detected temperature and the target temperature exceeds a predetermined value, the temperature control is performed without weighting the control amount. By changing the control so that weighting is performed thereafter, overshoot and ringing can be reduced and the target temperature can be quickly converged.

  Still further, in the analytical temperature control apparatus according to the present invention, the processing means is configured such that the polarity of the temperature difference between the detected temperature of each channel and the target temperature when the temperature detected by the temperature detecting means approaches the target temperature. It is preferable that the processing for reducing the control amount of any one of the channels is executed according to the above.

  That is, the polarities of the temperature differences in the plurality of channels are different from each other on the temperature control object, the part that has already exceeded the target temperature (has gone too far) and still has reached the target temperature. It means that there is no part. In this case, since signs of overshoot appear already, excessive overshoot can be suppressed as a whole by further reducing the control amount. However, in that case, if the control amount of the channel where the temperature difference from the target temperature is large is reduced, the temperature change that approaches the target temperature becomes slow, so it is less desirable to quickly converge to the target temperature. Absent. Therefore, it is preferable to reduce the control amount in a channel where the temperature difference from the target temperature is relatively small.

  According to the temperature control device for an analyzer according to the present invention, even when a target temperature that causes an extreme temperature change, such as an upper limit end or a lower limit end of the settable temperature range, is set, overshoot or ringing of the temperature change And the target temperature can be reached quickly. Therefore, for example, even when measurement is performed at regular time intervals, it is possible to perform measurement at a target accurate temperature. Further, when measurement is performed after stabilization at the target temperature, efficient measurement can be performed by shortening the waiting time until measurement. Furthermore, since the sample that is the object of temperature control does not reach a temperature that deviates from the predetermined temperature range, there is a situation in which the sample is denatured, an unintended reaction occurs, or the reaction proceeds at an unintended rate. Can be prevented.

  Hereinafter, as an embodiment of a temperature control device according to the present invention, a temperature control device for controlling the temperature of a sample cell of a spectrophotometer will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a temperature control apparatus of the present embodiment. In this apparatus, three Peltier elements 2a, 2b and 2c are attached to a predetermined position of the cell holder 1 which is a temperature control object, and the actual temperature of the cell holder 1 is detected in the vicinity of each Peltier element attachment position. Temperature sensors 3a, 3b and 3c which are platinum temperature measuring elements are provided. That is, the apparatus of this embodiment has heating / cooling means of three channels, the Peltier element 2a and the temperature sensor 3a are A channel (Ach), the Peltier element 2b and the temperature sensor 3b are B channel (Bch), and the Peltier element 2c. The temperature sensor 3c is a C channel (Cch).

  The temperature control device 4 includes a Peltier element driving unit 8 including a switching power supply using, for example, a MOS-FET switch to supply driving current to the three-channel Peltier elements 2a, 2b, and 2c, and the temperature of the three channels. It is included in the Peltier element driving unit 8 based on the temperature data reading unit 5 for reading temperature data from the sensors 3a, 3b, 3c simultaneously or almost simultaneously, and the target temperature Tj given from the temperature data and the control personal computer 9. An arithmetic processing unit 6 for calculating a duty ratio of a pulse signal for turning on / off the switch, and a pulse signal generating unit 7 for generating a pulse signal corresponding to the duty ratio and supplying the pulse signal to the Peltier element driving unit 8 .

  The arithmetic processing unit 6 stores a PID coefficient experimentally obtained based on the size of the cell holder 1 in advance, and calculates a duty ratio as will be described later by performing a PID calculation using this coefficient. Since the Peltier element driving unit 8 supplies a drive current corresponding to the duty ratio of the input pulse signal to the Peltier elements 2a, 2b, and 2c, the larger the duty ratio, the greater the duty ratio is supplied from the Peltier elements 2a, 2b, and 2c to the cell holder 1. The amount of heat generated (which can be regarded as giving positive heat in the case of heating and negative heat in the case of cooling) becomes large. That is, in this embodiment, the control amount in the present invention is the duty ratio.

  Next, the temperature control operation in the temperature control apparatus of the present embodiment will be described with reference to the flowchart of FIG.

  When the operator inputs and sets the target temperature Tj to the control personal computer 9 and gives an instruction to start control (step S1), the arithmetic processing unit 6 that receives this instruction via the control personal computer 9 starts the temperature control process ( Step S2). First, the arithmetic processing unit 6 sends an initial duty ratio predetermined for the three channels to the pulse signal generating unit 7. As a result, the Peltier element driving unit 8 supplies a drive current to the Peltier elements 2a, 2b, and 2c, and the Peltier elements 2a, 2b, and 2c start to heat or cool the cell holder 1 (step S3). In general, the initial duty ratio is the same for all channels.

  The temperature data reading unit 5 reads the temperature detected by the three temperature sensors 3a, 3b, and 3c at a predetermined time interval (100 msec in this case) and sends it to the arithmetic processing unit 6 (step S4). The arithmetic processing unit 6 calculates an average value of the three detected temperature data Ta, Tb, and Tc, and obtains a temperature difference ΔT between the average value data Tavg and the target temperature Tj (step S5). Then, it is determined whether or not the absolute value of the temperature difference ΔT is 2 ° C. or less (step S6). If the absolute value of the temperature difference ΔT is larger than 2 ° C., the temperature is changed without changing the duty ratio. The process returns to step S4 while continuing the control. When the target temperature Tj that is far away from the initial temperature T0 is set, the absolute value of the temperature difference ΔT always exceeds 2 ° C. for a while from the start of heating or cooling, so steps S4 → S5 → The process of S6 → S4... Is repeated, and the drive current corresponding to the initial duty ratio is continuously supplied to the Peltier elements 2a, 2b, 2c of each channel. Thereby, the temperature of the cell holder 1 rapidly rises or falls.

  When the actual temperature of the cell holder 1 approaches the target temperature Tj, it is determined in step S6 that the absolute value of the temperature difference ΔT is 2 ° C. or less, and the arithmetic processing unit 6 determines each detected temperature data Ta, Tb, Tc and the target temperature. The temperature differences ΔTa, ΔTb, ΔTc from Tj are calculated (step S7). The maximum temperature difference ΔTmax having the maximum absolute value and the minimum temperature difference ΔTmin having the minimum absolute value are extracted, and the absolute value of the maximum temperature difference ΔTmax is 0.2 ° C. or more and 2 ° C. or less. Further, it is determined whether or not the polarities of the maximum temperature difference ΔTmax and the minimum temperature difference ΔTmin are opposite (step S8).

Usually, even after the absolute value of the temperature difference ΔT becomes 2 ° C. or less, the absolute value of the maximum temperature difference ΔTmax does not become 2 ° C. or less for a while. Accordingly, the process proceeds to step S9 and subsequent steps, and the duty ratio is corrected by changing the weighting for the duty ratio of each channel. For this purpose, the arithmetic processing unit 6 compares the absolute values of the three temperature differences ΔTa, ΔTb, ΔTc calculated in step S7, and determines a weighting coefficient as follows according to the magnitude relationship (step S9). ).
(I) Channel with the smallest temperature difference: weighting factor 0.25
(Ii) Channel with the next smallest temperature difference: weighting factor 0.5
(Iii) Channel with the largest temperature difference: weighting factor 1

  When a new weighting coefficient for each channel is obtained in this way, the duty ratio is updated by multiplying the duty ratio of each channel at that time by the weighting coefficient (step S10). For example, the duty ratio does not change because the weighting coefficient is 1 in the channel having the largest temperature difference (iii), but the duty ratio is 0.25 because the weighting coefficient is 0.25 in the channel having the smallest temperature difference (i). It decreases to the previous quarter. The smaller the duty ratio is, the less driving power is supplied from the Peltier element driving unit 8 to the Peltier element, so the amount of heat given from the Peltier element to the cell holder 1 is smaller. Therefore, by updating the duty ratio in step S10, the amount of heat given from the Peltier element to the cell holder 1 is reduced in the channel where the difference between the actual temperature and the target temperature is small, and in the channel where the difference between the actual temperature and the target temperature is large. Even if the amount of heat applied from the Peltier element to the cell holder 1 is maintained or decreased, the degree of the decrease is small. As a result, the amount of heat is supplied in a well-balanced manner according to the actual temperature non-uniformity of the cell holder 1, and in particular, the amount of heat supplied to the portion where the temperature difference is small is suppressed, thereby making it difficult for overshoot to occur. It is very effective. Thus, once the absolute value of the temperature difference ΔT becomes 2 ° C. or less in step S6, the process of steps S7 → S8 → S9 → S10 → S4 → S5 → S6 → S7... Is repeated every 100 msec, thereby the cell holder 1 The actual temperature approaches the target temperature Tj.

  Eventually, the condition of step S8 is satisfied and the process proceeds to step S11. At this time, the temperature at which the temperature sensor 3a, 3b, 3c of any channel of the cell holder 1 is attached is considerably close to the target temperature Tj, but at least one temperature has exceeded the target temperature Tj. Since the overshoot of this temperature is nothing but overshoot, it can be considered that the sign of overshoot has already appeared at this time. Therefore, in order to prevent excessive overshoot, the duty ratio is reduced to reduce the amount of heat supplied to the cell holder 1 as a whole, but the duty ratio is reduced in a channel having a large temperature difference from the target temperature Tj. In this case, the temperature change that tends to approach the target temperature Tj becomes gentle, and it may take time to converge. For this reason, the channel closest to the target temperature Tj, that is, the channel having the minimum temperature difference ΔTmin is selected, and the duty ratio at that time of the channel is multiplied by 0.8 (step S11). As a result, the amount of heat supplied to the portion of the cell holder 1 that is closest to the target temperature Tj is further reduced, which is effective in suppressing overshoot.

  In this way, the temperature control is continued with the updated duty ratio (step S12), and if 1 second has elapsed, the temperature data reading unit 5 reads and calculates the temperatures detected by the three temperature sensors 3a, 3b, and 3c. The data is sent to the processing unit 6 (step 13). The arithmetic processing unit 6 calculates the temperature differences ΔTa, ΔTb, ΔTc between the detected temperature data Ta, Tb, Tc and the target temperature Tj by the process of step S14 similar to the above step S7, and the absolute value among them is calculated. The maximum temperature difference ΔTmax having the maximum value and the minimum temperature difference ΔTmin having the minimum absolute value are extracted, and it is determined whether or not the absolute value of the maximum temperature difference ΔTmax is 0.2 ° C. or less (step S15). . Here, when the absolute value of the maximum temperature difference ΔTmax is 0.2 ° C. or less, it is determined that the temperature of the cell holder 1 has substantially reached the target temperature Tj, and the purpose is to maintain the temperature substantially constant. The process proceeds to temperature control by the PID control.

  If the absolute value of the maximum temperature difference ΔTmax is not less than 0.2 ° C. in step S15, it is determined whether the polarities of the maximum temperature difference ΔTmax and the minimum temperature difference ΔTmin are opposite (step S16). If the polarity is reversed, the process returns to step S11, and if the polarity is not reversed, the process returns to step S12. That is, when the polarities of the maximum temperature difference ΔTmax and the minimum temperature difference ΔTmin are opposite, the duty ratio of the channel that is the minimum temperature difference ΔTmin at that time is further reduced by 20% to reduce the heat quantity for heating / cooling. If not, heating / cooling is performed while maintaining the previous duty ratio. As described above, since the process in step S13 is performed at 1 second intervals, the duty ratio update in step S11 is also performed at 1 second intervals, which is a period that is much longer than the duty ratio update by the previous weighting (100 msec intervals). It becomes.

  With the fine control as described above, the temperature control apparatus of the present embodiment can satisfactorily suppress overshoot and ringing even when the temperature of the cell holder 1 is suddenly raised or lowered.

The result of actual measurement with the apparatus having the above configuration will be described. FIG. 4 is a graph showing measurement results of actual temperature changes when the cell holder is controlled from 25 ° C. to 0 ° C. at a temperature drop rate of −5 [° C./min]. FIG. 5 is a graph showing measurement results of actual temperature changes when the same cell holder is controlled from 50 ° C. to 100 ° C. at a temperature increase rate of +5 [° C./min]. The cell holder in this measurement was an aluminum block (36 m ³ ) having a size of 20 × 20 × 90 mm, and three Peltier elements having an endothermic amount of about 12 W were used. As can be seen from the graphs of FIGS. 4 and 5, overshoot and ringing are sufficiently suppressed in both cases of temperature decrease and temperature increase, indicating an almost ideal temperature change. As a result, measurement at an accurate temperature is possible, and there is no fear of sample denaturation or undesired reaction, and good measurement is possible.

  Since the above embodiment is an example of the present invention, it is obvious that changes, modifications, and additions can be made as appropriate within the scope of the present invention. For example, although the above embodiment has a configuration with three channels, it is obvious that the present invention can be applied to two or more channels. The weighting coefficient may be determined as appropriate according to the number of channels, the heat capacity of the cell holder (which depends on the size and material), and the like.

The schematic block diagram of the temperature control apparatus by one Example of this invention. The schematic graph which shows the state of the temperature change when it heats up from initial temperature T0 to target temperature Tj with the conventional temperature control method. The control flowchart by the temperature control apparatus of a present Example. The graph which shows the measurement result of the actual temperature change at the time of temperature-fall control in the temperature control apparatus of a present Example. The graph which shows the measurement result of the actual temperature change at the time of temperature rising control in the temperature control apparatus of a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cell holder 2a, 2b, 2c ... Peltier element 3a, 3b, 3c ... Temperature sensor 4 ... Temperature control device 5 ... Temperature data reading part 6 ... Arithmetic processing part 7 ... Pulse signal generation part 8 ... Peltier element drive part 9 ... Control PC

Claims (4)

In the temperature control device for heating / cooling the sample to be analyzed in the analyzer via the temperature control object,
a) heating / cooling means of N (N is an integer of 2 or more) channel mounted on the temperature control object;
b) N-channel temperature detecting means for detecting the temperature of the temperature control object in the vicinity of the respective mounting positions of the N-channel heating / cooling means;
c) driving means for supplying driving power to the heating / cooling means independently according to the control amount given for each channel;
d) processing means for weighting the control amount given to the driving means for each channel according to the difference between each detected temperature by the temperature detecting means of the N channel and the target temperature;
A temperature control device for an analyzer, comprising:   The temperature control apparatus for an analyzer according to claim 1, wherein the heating / cooling means is a Peltier element.   When the difference between the temperature detected by the temperature detection means and the target temperature exceeds a predetermined value, the processing means does not perform weighting processing of the control amount for each channel, but when the difference is below the predetermined value The temperature control device for an analyzer according to claim 1 or 2, wherein the processing is executed.   The processing means reduces the control amount of any channel according to the polarity of the temperature difference between the detected temperature of each channel and the target temperature when the temperature detected by the temperature detecting means further approaches the target temperature. The temperature control device for an analyzer according to claim 3, wherein the temperature control device is executed.

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