JPH0675682B2 - Fluid sample temperature controller with constant temperature bath - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a temperature control device for effectively controlling the bath temperature of a constant temperature bath and the temperature of a liquid sample when measuring the viscosity of a liquid sample immersed in a constant temperature bath. Regarding

(Prior Art) When measuring the viscosity of a fluid sample, the temperature control of the sample is generally performed using a thermostatic bath. The temperature control is performed indirectly by using water, oil or the like as a heating / cooling liquid for the sample and controlling the temperature of the liquid.

(Problems to be Solved by the Invention) In the above conventional technique, it takes a long time to set the temperature of the fluid sample to a desired temperature. If you want to measure the viscosity of a fluid sample sequentially over a wide temperature range,
There was a problem that it was difficult to estimate the actual temperature of the same sample together with the change of the set temperature of the constant temperature bath.

For example, as described in Hiroo Kawada; "Viscosity", revised edition; Corona Publishing, Japan; 1983; page 41, in a capillary viscometer, the viscometer is immersed in a liquid bath of a thermostatic chamber. However, the liquid bath temperature is regarded as the temperature of the fluid sample in the viscometer. However, since the temperature of the sample cannot be directly measured despite the difference in the thermal conductivity depending on the sample, it takes a long time to obtain the relationship between the viscosity of the sample and the temperature.

In addition, as described on pages 109-110 of the above technical book, in the rotational viscometer, the sample container is surrounded by a water jacket, and water is circulated in the jacket from the water bath of the thermostat installed outside to measure the sample temperature. Are in control. In this case, the temperature control is performed on the water in the constant temperature bath, but since the temperature of the sample is not fed back to the temperature control of the constant temperature bath, it is not easy to bring the sample temperature to a desired set temperature. There was a point.

(Means for Solving the Problem) The present invention is intended to solve the problems of the above-mentioned conventional techniques.

The present inventors previously invented a new tuning fork vibration type viscometer,
This is disclosed in JP-A-59-107236 and US Pat. No. 4,729,237 issued Mar. 8, 1988. The present invention has been motivated by the desire to precisely and quickly control the temperature of a fluid sample when using this viscometer.

According to the present invention, when measuring the viscosity of a fluid sample, the temperature of the fluid sample is detected, the detected temperature is fed back to the temperature control of the constant temperature bath, and the temperature of the constant temperature bath is PID-controlled (proportional + integral + differential control). A temperature control means is provided.

According to the present invention, the temperature of a fluid sample can be effectively and promptly brought to a desired set value over a wide temperature range.

The present invention is a means for controlling the temperature of a fluid sample in a liquid bath, and comprises the following components. (A) a first for measuring the temperature of a fluid sample in a liquid bath
(B) a second means for determining the difference between the desired sample temperature and the measured sample temperature; and (c) an absolute value of the difference determined by the second means is predetermined. When the value exceeds the predetermined value, the first functional expression of the difference determined by the second means is in accordance with the P (proportional) control expression, and the absolute value of the difference determined by the second means is the predetermined value. If it is within the range, P ₁ as the second functional expression of the difference determined by the second means.
(D) third means for determining the desired bath temperature according to the (proportional + integral) control formula; (d) fourth means for determining the difference between the desired bath temperature and the desired sample temperature; (e) ) If the desired bath temperature determined by the third means exceeds the given value determined by the fourth means, then the desired sample temperature plus the given value. And if the difference determined by the fourth means is less than or equal to a negative number of the given value, then the given sample temperature is subtracted from the given value, Fifth for limiting each
(F) a sixth means for measuring the bath temperature; (g) a difference between the desired bath temperature and the measured bath temperature determined by the third and fifth means. Seventh means for determining; and (h) means for heating and cooling the liquid bath such that the difference is zero as a function of the difference determined by the seventh means. It is characterized by a fluid sample temperature control device using a constant temperature bath.

(Example) In FIG. 1, a fluid sample 3 whose viscosity is to be measured is contained in a sample container 4 and immersed in a liquid bath 8 of a constant temperature bath 1.
The viscosity sensor of the viscosity detector 2 and the temperature sensing part of the first thermometer 11 are immersed in the fluid sample 3, and the viscosity detector 2 and the first thermometer 11 are fixed to the stand 5. The temperature and viscosity of the fluid sample measured by the viscosity detector 2 and the thermometer 11 are counted and displayed by the recorder 7.
The recorder 7 outputs an output signal corresponding to the detected temperature of the fluid sample 3, and inputs this signal to the temperature measuring device 6 of the constant temperature bath 1.

In FIG. 2, a first thermometer 11 detects the temperature of the fluid sample 3, and a transmitter 12 attached to the first thermometer 11 outputs an output signal corresponding to the detected temperature of the fluid sample 3 (hereinafter (Referred to as a first output signal), and this signal is input to the first regulator 13. As the first thermometer 11, a resistance thermometer or a thermocouple thermometer including a platinum resistance wire or a thermistor is preferably used. The desired set point of the temperature of the fluid sample 3 is input to the first controller 13 by the input device 14 in advance. The first regulator 13 controls the temperature of the liquid bath 8 according to one of the first and second functional expressions expressed as a function of the difference between the desired set point of the fluid sample temperature and the detected value (varying over time). Calculate the set point. The first and second functional expressions will be described in detail later. The first regulator 13 emits one of the first and second regulation signals corresponding to the liquid bath set temperature respectively calculated by each of the two arithmetic circuits and inputs it into the second regulator 17.
The second thermometer 15 detects the temperature of the liquid bath 8, and the transmitter 16 attached to this thermometer emits an output signal (hereinafter referred to as the second output signal) corresponding to the detected temperature of the liquid bath 8 and outputs it. Input to the second controller 17. The second regulator 17 forms an operating signal corresponding to the level difference between this second output signal and the input regulating signal, and on the basis of this operating signal for PID control of the operation of the heating / cooling means 18. To generate a PID control signal formed by. The heating / cooling means 18 heats or cools the liquid bath 8 in response to the PID control signal.

As a result of a number of experiments, the above-mentioned first and second functional equations are obtained when the absolute value of the difference between the set temperature of the fluid sample and the detected temperature exceeds a predetermined temperature value, for example, 2 ° C. It has been found that it is preferable to carry out each if it is equal to or less than the predetermined temperature value. further,
The following general formulas (1) and (2) are preferably the first
It is used as a functional expression and a second functional expression.

Tbs = Ts + Kp × (Ts−Ms (i)) (1) and Tbs = Ts + Kp × (Ts−Ms (i)) + τ × K _I × ▲ Σ ⁱ _{j = 0} ▼ (Ts−Ms (j))
(2) where Tbs is the set temperature of the liquid bath, Ts is the desired set temperature of the fluid sample, τ is the control period defined as the time interval of successive determination of the set temperature of the liquid bath, Ms (i) and Ms (j) are respective fluid sample detection temperatures during the i-th and j-th repetitions of the control cycle after the operation of the temperature control means is started, Kp is a proportional constant, and Kp is a proportional constant. _I is an integration constant. The values of Kp and KI are obtained from the results of temperature control experiments conducted after selecting and adopting a constant temperature bath, a bath medium, a fluid sample container, etc. in advance. As can be understood from the above equation, the set temperature of the liquid bath changes according to the change in the detected temperature of the fluid sample.

In the present invention, the functions of the first and second regulators are preferably performed by a microcomputer programmed to perform these functions. Flowcharts of routines for performing these functions are shown in FIGS. 3 (a) and 3 (b). The program is designed to repeat this routine at regular time intervals.

In FIG. 3 (a), each iteration of the routine is step 50.
Starts at step 60 and ends at step 60. Hereinafter, in order to briefly describe each step of the routine, the terms “temperature value”, “set temperature”, “temperature deviation” and the like are used to mean electric signal levels corresponding to these. Step 51
In, the measured value Tbm of the temperature of the liquid bath 8 is the second thermometer 15
Given by. At step 52, the current n-of the routine
The liquid bath temperature deviation value Eb (n) in the second iteration is determined by the following step in the previous (i-1) -th control cycle.
It is determined as a value obtained by subtracting the value Tbm just given in step 51 from the liquid bath set temperature Tbs determined in 80 or 83. In step 53, the current liquid bath temperature deviation value Eb (n) just determined in step 52 and the previous liquid bath temperature value calculated in step 54 in the (n-1) -th iteration before the routine. The control force P is calculated by the PID algorithm using Eb (n-1). The control force P thus obtained is sent to the heating / cooling means 18, and the operation of the means 18 is controlled according to the control force P. At step 54, Eb (n) for use in the next (n + 1) -th iteration
The value of -1) is newly set equal to the value Eb (n). In step 55, the number of repetitions n is incremented by 1 in the counter.
In step 56, a timer measures the control time defined as the time that elapses until the number of repetitions becomes zero to n. In step 57, it is checked whether this control time is equal to or has not reached the predetermined control period τ, for example 10 seconds. If the control time has not reached τ, the program proceeds to step 58 and the third (b)
The subroutine 59 shown in the flowchart of the figure is skipped, and the process ends in step 60. The program repeats between steps 50 and 57 until the control time reaches the control period τ, eg 10 seconds. However, when the control time equals τ, the routine enters step 58. In step 58, after the control time reaches the control period τ, the calculation of the control time by the timer is cleared. That is, the timer resets to zero for a new measurement of the control time in the next iteration set of the routine. Then the subroutine 59 is started at step 70 as shown in FIG. 3 (b).

The subroutine is executed every time the timer of step 56 counts the control period τ, for example, 10 seconds. Step 71
Then, the measured value Ms (i) of the temperature of the fluid sample 3 is given from the first thermometer 11. In step 72, the fluid sample temperature deviation value Es (i) during the current i-th control cycle measured in step 56 is given in step 71 from the sample set temperature Ts determined by the operator of the control system. It is determined as a value obtained by subtracting the calculated value Ms (i). In step 73, the integrated value Is of the sample temperature deviation value Es (j) until j increases from zero to i with j as the number of repetitions of the control cycle
(I) is determined. In step 74, it is checked whether or not the absolute value | Es (i) | of the sample temperature deviation calculated in step 72 exceeds a predetermined temperature value, for example, 2 ° C. If this value | Es (i) | exceeds, for example, 2 ° C,
The subroutine enters step 75. On the other hand, this value is 2 ℃
The subroutine enters step 78 if: In step 75, if the value | Es (i) | exceeds 2 ° C., the integrated value Is (i) obtained in step 73 is cleared. Following step 75, the proportional term Kp * Es (i) is determined in step 76, where the constant Kp has been previously determined. Step
For 77, if | Es (i) | exceeds 2 ° C, set bath temperature Tbs
Is determined as the value obtained by adding the sample set temperature Ts to the proportional term obtained in step 76. Then, set the temperature difference between Tbs and Ts in Step 8
In step 82 obtained in step 1, this difference is compared with a given temperature value, for example 5 ° C. On the other hand, the value | Es (i) |
If it is found that the temperature does not exceed 2 ° C, the integral term τ × K _I × Is (i) is calculated in step 78.
K _I has already been determined. Following step 78, proportional term Kp ×
Es (i) is obtained again in step 79. In step 80, the bath set temperature Tbs in the current i-th control cycle is determined as a value obtained by adding the sample set temperature Ts to the sum of the terms obtained in steps 78 and 79. In step 81, the temperature difference ΔT is obtained by subtracting the sample set temperature Ts from the current bath set temperature Tbs. In step 82, the absolute value of the temperature difference │ΔT |
Is above a predetermined temperature value, for example 5 ° C. If this is above 5 ° C, the subroutine enters step 83. On the other hand, if the temperature is 5 ° C. or lower, the subroutine skips step 83 and goes directly to step 84. In step 83, the absolute value | ΔT | was found to exceed 5 ° C in step 81, then Tbs in step 80
Ignore the actual calculation result of and newly set the value of Tbs (Ts +
5) or (Ts-5). On the other hand, when the value | ΔT | is found to be 5 ° C. or less in step 82, the current bath set temperature Tbs is the value already obtained in step 80. The selection action is the liquid bath temperature with respect to the sample set temperature Ts in the transient period of the temperature control of the constant temperature bath 1.
Used to avoid unwanted overshoot or undershoot of Tbm. In step 84, the counter that counts the number of routine iterations n is set to zero. They or subroutines end at step 85 and the routine ends at step 60.

As shown in FIG. 3 (b) and as described above, the steps
The sample temperature deviation obtained in 72 is, for example, + 2 ° C or more or -2
If below ° C, the program skips steps 78-80 and performs steps 75-77 and 81 instead. Such a selection procedure is provided to effectively control the heating / cooling means 18 via the second regulator to heat or cool the liquid bath 8 so that the fluid sample temperature quickly approaches the sample set temperature. .

Next, the results of the temperature control experiment conducted using the temperature control means of the present invention will be described with reference to FIGS. Fig. 4-
In FIG. 6, A is the set temperature of the fluid sample. B is the measured temperature of the fluid sample, C is the liquid bath set temperature calculated in the first regulator, and D is the measured temperature of the liquid bath. These temperature AD were tracked by computer. As shown in FIG. 4, the temperature B of the fluid sample, which is an oily liquid of relatively high viscosity, is adjusted to the set point A of 30 ° C. after about 35 minutes and kept constant thereafter. FIGS. 5 and 6 show the experimental results obtained using a fluid sample having a lower viscosity and a higher thermal conductivity than the fluid sample used in the experiment whose results are shown in FIG. As shown in FIGS. 4 to 6, at the initial stage of each experiment, the set temperature C of the liquid bath was 5 ° C. higher than the set temperature of the fluid sample according to the temperature control program shown in FIG. 3 (b).
Are adjusted to be either high or low.

The heating / cooling means 1 according to the PID control signal formed in the second controller 17 based on the difference between the set temperature of the fluid sample and the measured temperature.
FIG. 7 shows the experimental results when the operation of 8 was controlled. In this experiment, the first controller 13 was not used, and signals corresponding to the set temperature of the fluid sample and the measured temperature were directly supplied to the second controller.
17 and the measured temperature of the liquid bath is not fed back to the second controller 17. As shown in FIG. 7, the liquid bath temperature D repeatedly oscillates considerably over time, so that the fluid sample temperature B also undulates with a considerable response delay and does not approach its set point even after a long time.

(Effect) According to the present invention, means for controlling the temperature of a fluid sample in a liquid bath; (a) a first for measuring the temperature of a fluid sample in a liquid bath
(B) a second means for determining the difference between the desired sample temperature and the measured sample temperature; and (c) an absolute value of the difference determined by the second means is predetermined. When the value exceeds the predetermined value, the first functional expression of the difference determined by the second means is in accordance with the P (proportional) control expression, and the absolute value of the difference determined by the second means is the predetermined value. If it is within the range, P ₁ as the second functional expression of the difference determined by the second means.
(D) third means for determining the desired bath temperature according to the (proportional + integral) control formula; (d) fourth means for determining the difference between the desired bath temperature and the desired sample temperature; (e) ) If the desired bath temperature determined by the third means exceeds the given value determined by the fourth means, then the desired sample temperature plus the given value. And if the difference determined by the fourth means is less than or equal to a negative number of the given value, then the given sample temperature is subtracted from the given value, Fifth for limiting each
(F) a sixth means for measuring the bath temperature; (g) a difference between the desired bath temperature and the measured bath temperature determined by the third and fifth means. Seventh means for determining; and (h) means for heating and cooling the liquid bath such that the difference is zero as a function of the difference determined by the seventh means. Therefore, the bath temperature of the constant temperature bath and the liquid sample temperature can be effectively controlled over a wide temperature range,
The sample temperature can be easily set to a desired set temperature.

[Brief description of drawings]

FIG. 1 is an external view of a thermostat for viscosity measurement equipped with the temperature control means of the present invention, FIG. 2 is an instrumentation flow sheet of the temperature control means of the present invention, and FIG. 3 (a) is the temperature control of the present invention. A routine flow chart of the preferred software program of the instrument, FIG. 3 (b) is a flow chart of the preferred subroutine used in the routine of FIG. 3 (a), and FIG. 4 is a flow chart of a liquid bath and fluid sample according to the present invention. Graphs showing experimental results of controlling each temperature, FIGS. 5 and 6 are graphs showing two other experimental results of controlling each temperature of the liquid bath and the fluid sample according to the present invention, and FIG. 7 is the present temperature control. FIG. 6 is a graph showing experimental results when the liquid bath is heated and cooled under the condition that the set point of the fluid sample temperature and the measured value are directly fed back to the second regulator without using the first controller in the means. . 1 ... Constant temperature bath, 2 ... Viscosity detector, 3 ... Fluid sample 4 ... Sample container, 5 ... Stand, 6 ... Temperature control device 7 ... Recorder, 8 ... Liquid bath, 11 ... 1st thermometer 12 …… Transmitter, 13 …… First controller, 14 …… Input device 15 …… Second thermometer, 16 …… Transmitter, 17 …… Second controller 18 …… Heating / cooling means

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hideaki Oshima 2-1-1 Tsukimi-cho, Kumagaya City, Saitama Chichibu Cement Co., Ltd. Central Research Laboratory (56) Reference JP-A-52-136436 (JP, A)

Claims (1)

[Claims] 1. A means for controlling the temperature of a fluid sample in a liquid bath; (a) a first means for measuring the temperature of a fluid sample in a liquid bath.
(B) a second means for determining the difference between the desired sample temperature and the measured sample temperature; and (c) an absolute value of the difference determined by the second means is predetermined. When the value exceeds the predetermined value, the first functional expression of the difference determined by the second means is in accordance with the P (proportional) control expression, and the absolute value of the difference determined by the second means is the predetermined value. If it is within the range, P ₁ as the second functional expression of the difference determined by the second means.
(D) third means for determining the desired bath temperature according to the (proportional + integral) control formula; (d) fourth means for determining the difference between the desired bath temperature and the desired sample temperature; (e) ) If the desired bath temperature determined by the third means exceeds the given value determined by the fourth means, then the desired sample temperature plus the given value. And if the difference determined by the fourth means is less than or equal to a negative number of the given value, then the given sample temperature is subtracted from the given value, Fifth for limiting each
(F) a sixth means for measuring the bath temperature; (g) a difference between the desired bath temperature and the measured bath temperature determined by the third and fifth means. Seventh means for determining; and (h) means for heating and cooling the liquid bath such that the difference is zero as a function of the difference determined by the seventh means. Fluid sample temperature control device using a constant temperature bath.