JPS5941021A - Controlling method of temperature in constant- temperature water tank - Google Patents

Abstract

PURPOSE:To set up constant temperature to a set temperature with high accuracy, by controlling the current supplying time width of a heater at each fixed period by the information of water temperature and the set temperature. CONSTITUTION:Current is supplied to the heater 4 set up in a constant-temperature water tank at each fixed period to heat water in the water tank 1. The water temperatures are detected by snsors 5, 8 and the periods when the water temperatures detected by the sensors 5, 8 are higher and lower than the set temperature are measured and a CPU10 controls the current supplying period of the heater on the basis of the measured periods. When the period that the water temperature is higher than the set temperature is continued, the CPU10 shortens the current conduction time of the heater 4 in accordance with the difference between the present water temperature and the set temperature. In case of continuation of the period that the water temperature is lower than the set temperature, current is supplied to the heater by the time width determined in accordance with the continuous time and the difference between the current water temperature and set temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a highly practical temperature control method for a constant temperature water tank that can simply and stably maintain the temperature of water in the constant temperature water tank.

[Technical background of the invention and its problems]

Conventionally, constant temperature water baths have been widely used in various research experiments and product inspections. This type of constant-temperature water tank is generally configured such that water filled in an adiabatic tank is heated by a heater, and the temperature is set and controlled using a meter relay or the like.

However, in the conventional devices described above, temperature errors were large because the temperature was generally set using a meter and then controlled. In addition, since a proportional control method according to a set temperature value is generally adopted, the temperature fluctuation is large and stability is poor. In order to solve these problems, various improvements and ideas have been made, such as making the water tank double-layered. However, this causes problems such as increasing the size of the constant temperature water tank and complicating the control system.
It lacked practicality.

[Purpose of the invention]

The present invention was made in consideration of these circumstances, and its purpose is to provide a simple and practical control system that can maintain a constant temperature of water in a high-precision constant-pressure water tank. The purpose of the present invention is to provide a temperature control method for a high constant temperature water tank.

[Summary of the invention]

The present invention detects the temperature of water in a constant temperature water tank heated by a heater that is energized at regular intervals, and measures the time when the temperature is higher than the set temperature and the time when it is lower than the set temperature. The energizing time of the heater is controlled according to the measurement results, and especially when the temperature continues to be higher than the set temperature, the energizing time of the heater is reduced according to the difference between the current water temperature and the set temperature. and when the temperature continues to be lower than the set temperature, the heater is energized for a time period determined by the duration and the difference between the current water temperature and the set temperature. be.

Therefore, according to the present invention, unlike the conventional proportional control method,
In addition to being able to set the constant temperature with high precision, the heater's energization time can be controlled by opening the time when the water temperature is higher than the set temperature and when it is lower than the set temperature, and controlling the energization time of the heater according to the time interval. Since the energization time of the heater is variably controlled depending on the continuation state of each time period, temperature ripples can be suppressed and the water in the aquarium can be kept at a constant temperature in a highly stable manner. Moreover, since the control system is simple, the system can be constructed easily and inexpensively, and has great practical advantages. With this method, the water in the aquarium can be kept at a constant temperature in a simple, highly accurate, and highly stable manner, resulting in tremendous effects.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a constant temperature water bath apparatus according to an embodiment, and FIG. 2 is a flowchart showing the temperature control sequence thereof. In Figure 1, 1 is, for example, 450''x350LX30
0H (wI) A water tank with a CD volume, generally made of a heat insulating material or the like.

A lid 2 made of a heat insulating material such as styrene resin is provided at the upper υδ mouth of the water tank 1. The lid 2 may be made of not only a heat insulating material, but also Bakelite, etc., which has poor thermal conductivity, or may be made of a material laminated with multiple layers of heat insulating material, or a material filled with a heat insulating material inside. I can do something. Thus, a sufficient amount of water is poured into the water tank 1 equipped with such a lid 2. Further, a stirrer 3 is provided in the water tank 1 to stir the water to make its temperature distribution uniform, and a heater 4 for heating the water is provided at the inner bottom of the water tank 1, and a heater 4 is also provided at the bottom of the water tank 1. Temperature sensors 5 for detecting the temperature of water are provided in the vicinity of 4, respectively. Further, a base thermometer 6 and an object to be measured 7 are detachably attached to the lid body 2 and are immersed in the water.

Further, a temperature sensor 8 for monitoring is provided near the object to be measured 7 of the water 4MZ. For this, aquarium 1
The water injected into the tank is heated by the heater 4 and sufficiently stirred by the stirrer 3 to make the temperature distribution uniform, and the temperature is detected by temperature sensors 5 and 8, respectively. Then, the energization time of the heater 4 is controlled as described later according to the detected temperature information.
The water is kept at a constant temperature.

Now, the temperature control system in this device is mainly composed of the control grosser 1o, as described below.

This control processor 1o is of a digital type, and includes, for example, a microcomputer or a so-called desktop computer. However, the lever control grosser 10 has a temperature setting key 11 consisting of a four-digit digital switch.
Accordingly, the temperature at which the water in the water tank 1 should be kept constant is input as (37,00)C, for example, in the form of BCD:ff'-. Further, the time information of a timer 12 that measures time in units of 0,011 is also manually inputted to the control glosser 10.

Note that this timer 12 is set in real time by a time set key 13.

The control processor 10 sets the flip-flop 14 so as to energize the heater 4 and raise the temperature of the water in the aquarium 1 as necessary. By this set of flip-flops 14, solid relay 15
is energized, and the heater 4 of the yacht is energized by the AC100V, 10ACI power source. In addition, in order to show the energization state of this heater 4,
In response to the set output of 4, the LED 16 is driven to turn on, and its status is input to the control processor 10. The converter 17 resets the flip-flop 14 and stops the energization of the heater 4. It compares the time information given from the processor 10 via the buffer 18 and the time information counted by the timer counter 19 and the timer 12, detects a match, and issues a reset signal to the flip-flop 14. There is. The operation of the solid relay 15 is controlled by the seven-rig flop 14 which is set and reset in this manner, and the heater 4 is heated by controlling the energization time at regular intervals.

By the way, the temperature sensors 5 and 8 are composed of, for example, thermistors, and their outputs are sent to linear live amplifiers 20.
21, where they are linearized and amplified. Note that this linearization is defined as linearization of the detection output characteristics with respect to the detected temperature of the temperature sensors 5 and 8 such as thermistors.Then, the detected temperature characteristics of the water linearized in this way are respectively Each of the differential amplifiers 22 and 230 is led to one input terminal. These differential amplifiers 22.23
The information on the set temperature outputted by the D/A converter 24 is input to the other input terminal, and the difference between the set temperature and the detected temperature is determined, and this is amplified and output. The above D/A converter 24
obtains from the processor 10 the digital information of the set temperature manually entered by the temperature setting key 11 and the multi-controller processor 10, converts it into an analog voltage, and applies the digital information to the differential amplifier 2.
2.23 respectively. Incidentally, the full converter 24 is provided with a variable resistor 25 for offset adjustment, so that the set temperature can be finely adjusted. Information on the difference between the detected temperature and the set temperature determined by the differential amplifier 22 is guided to the threshold circuit 27 after high frequency noise components are removed (via the low-pass filter 26). This threshold circuit 27 determines the polarity of the temperature information using, for example, zero potential as a threshold, and thereby determines whether the detected temperature is higher or lower than the set temperature. This determination result is shown as H and L, and the control processor 1
It is input to 0. Also, this status information is LE02g
It is used to drive light emission, and its status is monitored.

Further, the gain of the differential amplifier 23 is variably set according to the information output from the control processor 10. Information on the temperature difference amplified in accordance with the variably set gain is provided to a recorder 29 and is successively recorded. Incidentally, reference numeral 30 in FIG. 1 indicates a sound that is sounded under the control of the control processor 10, for example, when an abnormal situation occurs.

This device is constructed as described above, and by the action of the control processor 10, the set temperature tK information given from the temperature setting key 11, the time information obtained from the timer 12, and the differential amplifier 22 and threshold circuit 27 are processed. found through f
According to the status information H and L, the energization time width of the heater 4 is controlled at fixed time intervals, and the water in the water tank 1 is kept at a constant temperature.

Next, regarding the energization control of the heater 4 and the constant temperature control of the water in the water tank l by the control tube lO, the second
The explanation will be given according to the control sequence shown in the figure. However, the constants and times used in the following explanation were determined experimentally using the aquarium 1 having the specifications described above and the heater 4 of 100V, J, and OA. Therefore, if the specifications of the water tank 1 or the heater 4 change, it is of course necessary to change them.

First, for control, the entire control system is initialized (step 41). Next, the temperature setting key 1
Read the information of the set temperature set to 1 (step 4)
2). In accordance with the set temperature information Dtemp, control data Y is obtained in the control grosser 1° as follows, and a correction of 1 ky is added to this value Y as appropriate. The above value Y is Y=1280.36XDtemp 69164.1
2 ---(ri), and the correction amount y is y=-7,937(Dtemp -37,1)X(Dt
emp-41) −(2). Note that the above correction fity is added only when the set temperature exceeds 37.1'C. The value Y obtained in this way is
It is used as the internal set temperature fK information of the grossep 10.

Because of this, the output characteristics of the temperature sensor and the output characteristics of the above D/A are matched? That means you did it.

According to such set temperature information, the necessary converter 24 obtains voltage signals corresponding thereto, and outputs them to the differential amplifiers 22 and 23, respectively. As a result, the difference between the temperature of the water detected by the temperature sensors 5 and 8 is determined, and the threshold circuit 27 determines whether the temperature of the water is higher than the set temperature (status H) or lower (status H).
The task L) will be determined. In Grossessa IO,
Information such as is read in the form of a status, and it is determined whether the status is H or not (step 43). If status H is detected in this determination, a message is output to cool the water in the aquarium 1 or to prompt a change in the temperature setting. (
STETSU f44). Note that water cooling can be performed not only by natural cooling, but also by injection work to lower the tank temperature.

On the other hand, if the status L is detected by the above determination, the flip-flop 14 is set and the heater 4 is energized (step 45). This heater 4 is normally energized for about 2 hours, and as a result, the temperature of the water is reduced to room temperature (2.
5°C) to the set temperature (for example, 37°C). After that, the status is determined (step 46).
), status 1■ is detected and the heater 4 is turned off (step 47). In this state, the situation is observed for a while to avoid a transient temperature rise, and then the status is determined again (step 48). Then, when the status is H, the output value of the first converter 24 is varied to find the value Y' at the point where the status changes to L, and this information value Y
' by inversely bounding the equations (0 and (2)),
Determine the current temperature (step 49), and when the current temperature is sufficiently close to the set temperature value, the differential amplifier 2
Set the gain of step 3 high (step 50), and set the gain of step 3 high.
0 to inform the operator that preparation is complete (step 51).

Next, initial settings for control are performed (step 52), and a control constant CK is determined according to the following equation (step 53).

Ck=0.2+exp((Dtemp-30)/'20
1) --- (3) This control constant Ck is determined in order to match the slope characteristics of the time required for the temperature of the water in the water tank 1 to rise and the time required for the temperature to fall. After that, the current time is read from the timer 12 (Stetsuno 54
), and then it is determined whether or not the temperature setting value can be changed (step 55). If a change in the set value is recognized, the routine from step 42 is repeated, but since there is generally no change in the set value, a self-diagnosis is performed (step 56). This self-diagnosis is performed by confirming that the current temperature is above the set temperature value and that the heater 4 is not energized for a certain period of time, for example, 2 seconds or more. This is a measure to prevent the tank temperature from becoming abnormally high due to the self-running of the heater 4. If this diagnostic result is abnormal, for example, step 42
It goes without saying that measures will be taken, such as retrying the process from the beginning.

Next, when the above self-diagnosis is completed, it is determined whether the status is H or not (step 57).
In this case, the heater 4 is turned off (step 58). Next, it is determined whether the status checked last time was also H (step 59). At this point, step 5
2, since the status H is initially set, the time during which the status H continues is cumulatively determined (step eo). This time is from the time when the time was read in step 54 above. Then, in step 61, it is determined whether this time Hj has reached a certain value.
), when the result is NO, the process returns to step 56.

Then, as this process is repeated, a YES determination result is obtained, so the process proceeds to processing route 62 at this time. In this route 62, first, the setting value of the converter 24 is changed until the status changes from H to L, and then the equations (1) and (2) are converted into inverse Korean expressions according to the setting value at this point. to find the current temperature. After that, the heater 4 is energized for a time T. Measure n and reduce the energization time. This decreasing time is Ton(h)""Ton(h)(1((ΔT-0,01
) *25+5 )/1oo)...(4). The energization time Ton of the heater 4 is given, for example, 1 second as an initial value, and the energization time of the heater 4 is as follows.
Each time the above-mentioned time elapses, it is sequentially decreased. This processing routine is repeated until status L is detected in step 57.

Therefore, when the time has elapsed, the status L is determined in step 57. In this state, the previous status is determined (step 63). At this time, since the previous status was H, the process proceeds to processing route 64. In this processing route, it is determined whether or not the time Hj at which the status was divided by H was 0 (Stella f65), and if the time is 0, the initial value of the information is set as is (Stella f66). ). Further, if the above-mentioned time Hj is not 0, the information regarding the status in the previous and two previous judgments is shifted respectively to prepare for the next process (step 67),
The process advances to step 66 and returns to step 55.

The information regarding the status to be shifted is defined as the point in time when the status changes from ■( to L and from L to H. By repeatedly executing such a processing routine, Step 6 when
3, it is determined that the previous status was L. In this case, the process proceeds to step 67, and the time Lt during which the status is L is measured.

Thereafter, it is determined whether the heater 4 is to be brought into the open state or not if the clamp 5c=1 (step 68). At this point, the heater 4 is not turned on, so
With Stella 7″69, the time since the last heater was turned on is 1.
It is determined whether 0 seconds or more have elapsed. And 10
When seconds have elapsed, K proceeds to step 7o and determines in what form the energization of the heater 4 should be controlled.

In this case, at the beginning, YE is set by the initial setup.
Since the root of S has been specified, the process proceeds to step 71 and the value Sum is determined according to the following equation.

5ull+”'ΣCCkTb+-Tt1) XWi
--=, (5) i:1 'rhi' is the time (It)T of the th status H
ti” time of status L (Lt) W4:i
This equation (5) combines the slope characteristics of temperature rise and fall,
91'r means that a predetermined weight is applied to the time difference between statuses H and L in the fourth position, and the above weight W,
The first. Second. For the third past (0, 6
), (0,3), (0,1), etc. After that, Stella! determines the polarity of the value Sum obtained as above! 72), whether to set the control value β (→-1) or (
Step 73), it is determined whether Rurui t is set to (-1) (Step 74). Thereafter, using the f[i control value β of and, in step 75, the energization time T of the heater 4 is determined as follows. Find n.

Ton=Ton(h)/100-4(), 04069X
βXexp (la+shoulder X0.2059)・・・・・・
(6) Information indicating the energization of the heater 4 (SC=t) is then set (step 76) and the calculated time T. The heater 4 is energized according to n (step 77). Then, the control loop counter is incremented, etc., and the process returns to step 55 to repeat the above-described process.

When this loop is reprocessed again, the processing route is changed in step 68 since the sc is set to "1". In this case, in step 78,
The time is determined to take the status H state.

When this judgment step 78 is reached for the first time, since the passage of time is naturally short, a negative judgment is made and the process returns to step 55. Then, when a predetermined time has elapsed, the process proceeds to the next step 79.

However, while waiting for the above-mentioned time, the processing routine may change depending on the determination at step 57. Then, in step 79, the output of the temperature converter 24 is changed again to measure the actual temperature as described above. Then, the difference ΔT between the measured current temperature of the water and the set temperature is determined (depending on the magnitude of this temperature difference ΔT), and a treatment route is determined (step SO). One is when the current temperature becomes close to the set temperature for the first time, or when it deviates significantly from the set temperature due to a disturbance. , in the control mode, if the temperature difference ΔT is relatively small, step 8
Proceed to step 2. In step 81, T01=0.2768Xexp(8,087XΔTxV
τ4 stones) −・−−−−−(7),
The energization time of the heater 4 is determined. In addition, at step 82, Ton” (40XΔt+0.1)X〆σn−−−−・
-...(s) is the energization time of the heater 4.

However, the above t indicates the duration of status L.

Note that the energization time T calculated in this way. If only n is used, the heater 4 may have to be energized for quite a long time, so the maximum energization time is limited to 2 seconds.
This divides the energization control into two systems (step 83
). And the energization time T. If n is less than 2 seconds, the processing routine 84 measures the energization time of the heater 4 a and energizes the heater 4 until the time reaches the above-mentioned time ToH. Then, this process is completed and the process returns to step 56. If the time Ton is 2 seconds or more, the heater 4 is energized for 2 seconds in step 85, and then the process returns to step 55.

By energizing the heater 4 in this manner, the temperature of the water rises, at which point the status becomes H. At this point, the processing routine advances from Stella f57 to Step 59, and since the previous status is L, the processing routine advances to processing routine 86. In this processing routine, data is shifted, that is, past data is updated in the same manner as in routine 64, in preparation for the next processing process.

Through the process shown above, the energization time width T of the heater 4 is determined for each fixed time period. n is controlled according to information about the water temperature and the set temperature (status state and its duration, etc.). Furthermore, the current energization time of the heater 4 is controlled 8 by taking into consideration the current and past control states. Therefore, the tank temperature can be kept constant at the set temperature with high precision, and the temperature ripple can also be suppressed to a low value of, for example, 0.01° C. or less. Furthermore, the constant temperature setting temperature can be digitally set and input with high precision, and performance can be dramatically improved compared to the conventional meter relay. In addition, since it is essentially different from the conventional proportional control system, the controllability is good11), and the configuration of the control system is simple, which provides great practical effects.

Note that the present invention is not limited to the above embodiments. For example, various constants in a control system are determined experimentally and are not unique. Moreover, even if the constant value fluctuates to some extent, it will not cause any essential problems in its controllability. Furthermore, if a suitable D/AK converter 24 is used, an error of about ±0.02°C will occur between the set value and the control value determined according to equations (1) and (2). In such a case, the variable resistor 25 may be used to finely adjust the K value. In this way, a very good constant temperature water tank can be realized. It goes without saying that the water tank 1 may be of a double layer type. In short, the present invention can be implemented with various modifications without departing from the gist thereof.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a constant temperature water bath apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram showing a temperature control sequence in the embodiment. 1...water tank, 4...heater, 5.8...temperature sensor,
IO...Control grosser, 11...Temperature setting key,
12...Timer, 14...7 reset log, 1
7... Comparator, 22... Differential amplifier, 24...
...1 converter, 27...threshold circuit.

Claims (1)

[Claims] A heater that is energized at regular intervals to heat the water in the constant temperature water tank, a temperature sensor that detects the temperature of the water, and a temperature sensor that detects the time when the temperature of the water detected by this temperature sensor is higher than the set temperature and and a control system that controls the energization time of the heater by measuring the time when the temperature is lower than the set temperature, and the control system is configured to adjust the temperature according to the difference between the current water temperature and the set temperature when the set temperature continues for a period of time when the set temperature is higher than the set temperature. Reduce the energization time of the heater, and when the temperature continues to be lower than the set temperature, energize the heater for a time period determined according to the duration and the difference between the current water temperature and the set temperature. A temperature control method for a constant temperature water tank that is characterized by: