CA1332292C - Temperature controlling means for a thermostat for use in measuring viscosity - Google Patents
Temperature controlling means for a thermostat for use in measuring viscosityInfo
- Publication number
- CA1332292C CA1332292C CA000589963A CA589963A CA1332292C CA 1332292 C CA1332292 C CA 1332292C CA 000589963 A CA000589963 A CA 000589963A CA 589963 A CA589963 A CA 589963A CA 1332292 C CA1332292 C CA 1332292C
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- fluid sample
- set point
- thermostat
- heating
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- 239000012530 fluid Substances 0.000 claims abstract description 61
- 238000001816 cooling Methods 0.000 claims abstract description 22
- 238000010438 heat treatment Methods 0.000 claims abstract description 22
- 239000007788 liquid Substances 0.000 claims description 16
- 238000005259 measurement Methods 0.000 abstract description 2
- 239000000523 sample Substances 0.000 description 63
- 230000001276 controlling effect Effects 0.000 description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 238000002474 experimental method Methods 0.000 description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 102100029469 WD repeat and HMG-box DNA-binding protein 1 Human genes 0.000 description 1
- 101710097421 WD repeat and HMG-box DNA-binding protein 1 Proteins 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
- B01L7/00—Heating or cooling apparatus; Heat insulating devices
- B01L7/02—Water baths; Sand baths; Air baths
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
- G01N11/10—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by moving a body within the material
- G01N11/14—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by moving a body within the material by using rotary bodies, e.g. vane
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D23/00—Control of temperature
- G05D23/19—Control of temperature characterised by the use of electric means
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
- G01N2011/0006—Calibrating, controlling or cleaning viscometers
- G01N2011/002—Controlling sample temperature; Thermal cycling during measurement
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- Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Biochemistry (AREA)
- Analytical Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Engineering & Computer Science (AREA)
- Automation & Control Theory (AREA)
- Clinical Laboratory Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Control Of Temperature (AREA)
Abstract
ABSTRACT
Temperature controlling means for a thermostat for use in viscosity measurement including: a first thermometer detecting the temperature of a fluid sample which is immersed in a thermostat and whose viscosity is measured; a first controller obtaining the difference between a desired set point and the detected value of the sample temperature, momently calculating a set point of temperature of the thermostat according to an operation formula expressed as a function of the above temperature difference and making a controlled signal corresponding to the calculated set point; a second thermometer detecting the temperature of the thermostat; a heating and cooling device for heating and cooling a medium bath of the thermostat; and a second controller making a controlled signal for operating the heating and cooling device under a PID
control formed on the basis of the difference between the calculated set point and the detected value of the thermostat temperature and inputting the PID controlled signal into the heating and cooling device.
Temperature controlling means for a thermostat for use in viscosity measurement including: a first thermometer detecting the temperature of a fluid sample which is immersed in a thermostat and whose viscosity is measured; a first controller obtaining the difference between a desired set point and the detected value of the sample temperature, momently calculating a set point of temperature of the thermostat according to an operation formula expressed as a function of the above temperature difference and making a controlled signal corresponding to the calculated set point; a second thermometer detecting the temperature of the thermostat; a heating and cooling device for heating and cooling a medium bath of the thermostat; and a second controller making a controlled signal for operating the heating and cooling device under a PID
control formed on the basis of the difference between the calculated set point and the detected value of the thermostat temperature and inputting the PID controlled signal into the heating and cooling device.
Description
^` 1 3322q~
1 TITLE OF THE INVENiION
TEMPERATURE CONTROLLING MEANS FOR A THERMOSTAT FOR
USE IN MEASURING VISCOSITY `
FIELD OF THE INVENTION
The present invention relates to temperature controll-ing means for a thermostat, and more particularly to temper-ature controlling means by which, in measuring the viscosity of a fluid sample immersed in a bath of the thermostat, the temperatures of the bath and the fluid sample are effectively controlled over a wide temperature range.
BACKGROUND OF THE INVENTION
In measuring the viscosity of a fluid sample, the temperature of the fluid sample is generally controlled by using a thermostat. A liquid bath comprising water, oil or the like is used as a medium for heating and cooling the fluid sample, and the temperature of the fluid sample is indirectly controlled through regulation of the temperature of the medium. Therefore, it requires a lot of time to adjust the fluid sample temperature to a desired set point.
In addition, when the viscosity of the fluid sample is sequentially measured over a wide temperature range, it may be difficult to estimate the actual temperature of the sample varying with time after changing the set point of the medium ,\s :~.`',:: , : ~ ' :
~.i . ~ ' ' : :. : ' ~ 3322q2 temperature.
For example, in a capillary viscometer, the viscometer is immersed in a medium bath of a thermostat, and the temperature of the medium bath is regarded as the temperature of a fluid sample within the viscometer. However, because the temperature of the sample cannot be directly measured in addition to the fact that the heat conductivity of the sample differs with the kind of the sample, it takes a long time to correctly determine a relationship between viscosity and temperature of the sample.
Also, in a rotation viscometer, a sample container is surrounded by a water jacket, and water is forcedly circulated between the jacket and a water bath of a thermostat installed outside the jacket to control the temperature of the sample.
In this case, temperature controlling is carried out with respect to the water in the thermostat without feedback of the temperature of the sample to the temperature controlling of the thermostat. It is, therefore, not easy to adjust the sample temperature to a desired set point.
SUMMARY OF THE INVENTION
It is an object of the present invention to remove these drawbacks as noted above with respect to prior art.
The present inventors have previously invented a novel tuning fork vibration-type viscometer and have disclosed it A
~ . . . . . .
~` 1 3322q2 1 in Japanese Laid-Open Patent Application No. 107236/1984 and U.S. Patent No. 4,729,~37 issued March 8, 1988. Particularly ¦ stimulated by a desire to precisely speedily control the ¦ temperature of a fluid sample whose viscosity is to be measured in using such novel viscometer, the inventors has accomplished the present invention.
The present invention provides temperature controlling means wherein, in measuring the viscosity of a fluid sample, the temperature of the fluid sample is detected and the detected temperature is fed back to temperature controlling of a thermostat and the temperature of the thermostat is subjected to a PID (proportional + integral + differential) control.
According to the present invention, the temperature of the fluid sample can be effectively speedily adjusted to any desired set point in a wide temperature range.
The temperature controlling means of the present invention comprises:
a first thermometer detecting the temperature of a fluid sample immersed in a medium bath of a thermostat and having means for making a first output signal corresponding to the detected temperature of the fluid sample;
a first controller receiving the first output signal from the first thermometer and an input command corresponding a ~esired set point of temperature of the fluid sample, .. . - : . , :
~,: . . - ' ' :
,,~, . .
t 3322q2 ~1 and determining a set point of temperature of the medi~m bath according to an operation formula expressed as a function of difference between the set point of the fluid sample temperature and the detected value of the ~luid sample temperature and making a first controlled signal corresponding to the determined set point oÇ temperature of the medium b3th;
a second thermometer detecting the temperature of the medium bath and having means for making a second output signal corresponding to the detected temperature of the medium bath;
heating and cooling means for heating and cooling the medium bath; and a second controller receiving the second output signal from the second thermometer and the first controlled signal from the first controller and forming an actuating signal corresponding to the difference in level between the first controlled signal and the second output signal and subsequently inputting a PID controlled signal formed on the basis of the actuating sisnal to the heating and cooling means.
In a further aspect, the present invention relates :~:
to a temperature controlling means for automatically controlling the temperature of a fluid sample for measuring viscosity of the fluid sample, said fluid sample being immersed in a liquid bath of a thermostat, said temperature controlling means comprising~
a first thermometer means for detecting the temperature of the fluid sample and producing a first output signal corresponding to the detected temperature of the fluid sample;
, ~, ~ .- , - - , :~ - .. ..
' ' ; '' ' , '' ' -, ~ :'' ' ' -~ a first controller for receiving the first output signal and an input command corresponding to a desired set point temperature of the fluid sample, determining a set point temperature of the liquid bath according to an operation formula expressed as a function of the difference between the desired set point temperature of the fluid sample and its detected temperature and producing a first controlled signal corresponding to the li~uid bath set point temperature determined by carrying out the operation formula;
a second thermometer means for detecting the temperature of the liquid bath and for producing a second output signal corresponding to the detected temperature of the liquid bath;
heating and cooling means for heating and cooling the liquid bath; and a second controller for receiving the second output signal and the first controlled signal and forming an actuating signal corresponding to the difference in level between the first controlled signal and the second output signal and subsequently inputting to the heating and cooling means a PID controlled signal formed on the basis of the actuatinq signal, the heating and cooling means being operative to heat and cool the liquid bath according to the PID controlled signal inputted thereto.
As clearly understood from the above-described :
construction and functions, the present temperature controlling means comprises a cascade control system. The first controller is provided with an operation circuit for calculating a timely suitable set point (which varies with time) of temperature of .
the thermostat in response to the detected temperature (which changes with time) of the fluid sample so that the fluid sample ~
..
-:- : . ~ :
1 3322q2 1 may be effectively heated or cooled by the thermostat,according to the detected temperature of the fluid sample, so as to speedily adjust the temperature of the fluid sample to its desired set point. The operation formula on which the operation circuit is based is expressed as a function of the difference between the set point of and the detected value of temperature of the fluid sample and the details thereof are experimentally determined according to the thermostat to be used, the kind of bath medium used therefor, the fluid sample container to be immersed in the medium and so forth. Moreover, the heating and cooling of the thermostat are effectively controlled according to a PID action formed in the second controller.
: .
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an external view of a thermostat for use in ~-viscosity measurement, which is provided with temperature controlling means embodylng the present invention;
FIG. 2 is an instrumentation flow sheet of temperature controlling means embodying the present invention;
FIG. 3 is a graph of an experimental result of controlling the temperatures of a medium bath and a fluid sample in accordance with the present invention; and FIG. 4 is a graph of an experimental result of heating and cooling the medium bath under the conditions that the set : .
, - : -~ ~ ' ' ' ' ' ':- ' ' :', - . :
. : : . :
,,:, .. ~ - : . - . . .. . . . :
1 point and the detected value of temperature of the fluid sample are directly fed back to a second controller in the present temperature controlling means without using a first controller in the present temperature controlling means.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring to FIG. 1, a fluid sample 3 whose viscosity is to be measured is received in a sample container 4 and immersed in a medium bath 8 of a thermostat 1. A viscosity sensor of a viscosity detector 2 and a temperature probe of a thermometer 11 are immersed in the fluid sample 3, where the viscosity detector 2 and the thermometer 11 are held by a stand 5. The temperature and viscosity of the fluid sample 3 detected by the detector 2 and the thermometer ll,respectively, are counted and displayed by a recorder 7. The recorder 7 makes an output signal corresponding to the detected temperature of the fluid sample 3 and inputs said signal into a temperature control device 6 of the thermostat 1. The control device 6 includes first and second controllers 13 and 17 which are described hereinafter. Also, reference numerals 18 and P designate heating and cooling means for the medium bath 8 and a pump for circulating the medium bath 8 to stir it.
- 6 - /cont. ...6a j?~
---` 1 3322q2 1 The temperature controlling means according to the present invention will be described with reference to FIG. 2.
The first thermometer 11 detects the temperature of the fluid sample 3, and a transmitter 12 attached to the first thermometer makes an output signal (hereinafter referred to as a first output signal) corresponding to the detected temperature of the fluid sample 3 and inputs the first output - 6a - /cont. ...7 .' .
:.~; . ~ , - . . :
1 signal into a first controller 13. As the first thermometer 11, a resistance thermometer composed of a platinum resistance wire or a thermistor or a thermocouple thermometer is preferably used. A predetermined set point of temperature of the fluid sample 3 is inputted in advance into the first controller 13 by an inputting means 14. The first controller 13 has an operation circuit which calculates a set point of temperature of the medium bath 8 according to an operation formula expressed as a function of difference between the predetermined set point of and the detected value (which changes with time) of the fluid sample temperature. The first controller 13 makes a controlled signal thereinafter referred to as a ~ :
first controlled signal) corresponding to the set point of the medium bath temperature calculated by the operation circuit and inputs the first controlled signal into a second controller 17. A second thermometer 15 detects the temperature of the medium bath 8, and a transmitter 16 attached thereto makes an output signal (hereinafter referred to as a second output signal) corresponding to the detected temperature of the medium bath 8 and inputs the second output signal into the second controller 17. The second controller 17 forms an actuating signal corresponding to the difference in level between the first controlled signal and the second output signal and makes a controlled signal (hereinafter referred to as a second controlled signal) formed on the basis of the actuating signal 1 332~q~
1 for a PID control of operation of heating and cooling means 18. The heating and cooling means 18 heats and cools the medium bath 8 in response to the second controlled signal. --It has been found to be preferable, as a result of a lot of experiment, that as the aforesaid operation formula for S calculating the set point of temperature of the medium bath 8, the following general expression is used in the present invention:
T~ = TS + Kp(Ts - MS(~ ~ KI (Ts ~
J-D
where T~ represents the set point of the medium bath temperature, TS represents the set point of the fluid sample temPeratUre' Ms(i) and Ms(j) the respective detected temperatures of the fluid sample at time i and i after starting the temperature controlling means to operate, Kp a proportional constant, KI an integral constant, and1~ a control period.
The values of Kp and KI are determined from the results of temperature control experiments which have been done upon preselection and preadoption of a thermostat, a bath medium, a fluid sample container and the like to be used. As understood from the above expression, the set point of the medium bath temperature to be fed back to the second controller 17 is changed with variation in the detected temperature of the fluid sample. ~
Next, a result of a temperature control experiment .
t 332292 carried out using the temperature controlling rneans in accordance with the present invention will be described with reference to FIG. 3. In FIG. 3, A designates the set point of temperature of a fluid sample, in which case the set point is 30C. B
denotes the detected temperature of the fluid sample, C the set point of a medium bath calculated by the aforementioned first controller, and D the detected temperature of the medium bath. The fluid sample used is an oil liquid. These temperatures A to D were pursued by a computer. As shown in FIG. 3, the temperature B of the fluid sample is adjusted to its set point A after about 35 minutes and then kept constant.
For comparison, FIG. 4 shows an experimental result when the operation of the heating and cooling means 18 is controlled according to a PID controlled signal formed, on the basis of the difference between the set lS point of and the detected value of temperature of a fluid sample, in the second controller 17. In this experiment, however, the first controller 13 is not used, and the signals of the set point and detected value of the fluid sample temperature are directly inputted into the second controller 17, where the detected temperature of a medium bath is not fed back to the second controller 17. As shown in FIG.
4, the temperature D of the medium bath repeatedly considerably fluctuates with time, and thereby the temperature 8 of the fluid sample also waves with a considerable delay of response and does not approach to its set point even after a lon~ time.
_ g _ ~ ~.
1 TITLE OF THE INVENiION
TEMPERATURE CONTROLLING MEANS FOR A THERMOSTAT FOR
USE IN MEASURING VISCOSITY `
FIELD OF THE INVENTION
The present invention relates to temperature controll-ing means for a thermostat, and more particularly to temper-ature controlling means by which, in measuring the viscosity of a fluid sample immersed in a bath of the thermostat, the temperatures of the bath and the fluid sample are effectively controlled over a wide temperature range.
BACKGROUND OF THE INVENTION
In measuring the viscosity of a fluid sample, the temperature of the fluid sample is generally controlled by using a thermostat. A liquid bath comprising water, oil or the like is used as a medium for heating and cooling the fluid sample, and the temperature of the fluid sample is indirectly controlled through regulation of the temperature of the medium. Therefore, it requires a lot of time to adjust the fluid sample temperature to a desired set point.
In addition, when the viscosity of the fluid sample is sequentially measured over a wide temperature range, it may be difficult to estimate the actual temperature of the sample varying with time after changing the set point of the medium ,\s :~.`',:: , : ~ ' :
~.i . ~ ' ' : :. : ' ~ 3322q2 temperature.
For example, in a capillary viscometer, the viscometer is immersed in a medium bath of a thermostat, and the temperature of the medium bath is regarded as the temperature of a fluid sample within the viscometer. However, because the temperature of the sample cannot be directly measured in addition to the fact that the heat conductivity of the sample differs with the kind of the sample, it takes a long time to correctly determine a relationship between viscosity and temperature of the sample.
Also, in a rotation viscometer, a sample container is surrounded by a water jacket, and water is forcedly circulated between the jacket and a water bath of a thermostat installed outside the jacket to control the temperature of the sample.
In this case, temperature controlling is carried out with respect to the water in the thermostat without feedback of the temperature of the sample to the temperature controlling of the thermostat. It is, therefore, not easy to adjust the sample temperature to a desired set point.
SUMMARY OF THE INVENTION
It is an object of the present invention to remove these drawbacks as noted above with respect to prior art.
The present inventors have previously invented a novel tuning fork vibration-type viscometer and have disclosed it A
~ . . . . . .
~` 1 3322q2 1 in Japanese Laid-Open Patent Application No. 107236/1984 and U.S. Patent No. 4,729,~37 issued March 8, 1988. Particularly ¦ stimulated by a desire to precisely speedily control the ¦ temperature of a fluid sample whose viscosity is to be measured in using such novel viscometer, the inventors has accomplished the present invention.
The present invention provides temperature controlling means wherein, in measuring the viscosity of a fluid sample, the temperature of the fluid sample is detected and the detected temperature is fed back to temperature controlling of a thermostat and the temperature of the thermostat is subjected to a PID (proportional + integral + differential) control.
According to the present invention, the temperature of the fluid sample can be effectively speedily adjusted to any desired set point in a wide temperature range.
The temperature controlling means of the present invention comprises:
a first thermometer detecting the temperature of a fluid sample immersed in a medium bath of a thermostat and having means for making a first output signal corresponding to the detected temperature of the fluid sample;
a first controller receiving the first output signal from the first thermometer and an input command corresponding a ~esired set point of temperature of the fluid sample, .. . - : . , :
~,: . . - ' ' :
,,~, . .
t 3322q2 ~1 and determining a set point of temperature of the medi~m bath according to an operation formula expressed as a function of difference between the set point of the fluid sample temperature and the detected value of the ~luid sample temperature and making a first controlled signal corresponding to the determined set point oÇ temperature of the medium b3th;
a second thermometer detecting the temperature of the medium bath and having means for making a second output signal corresponding to the detected temperature of the medium bath;
heating and cooling means for heating and cooling the medium bath; and a second controller receiving the second output signal from the second thermometer and the first controlled signal from the first controller and forming an actuating signal corresponding to the difference in level between the first controlled signal and the second output signal and subsequently inputting a PID controlled signal formed on the basis of the actuating sisnal to the heating and cooling means.
In a further aspect, the present invention relates :~:
to a temperature controlling means for automatically controlling the temperature of a fluid sample for measuring viscosity of the fluid sample, said fluid sample being immersed in a liquid bath of a thermostat, said temperature controlling means comprising~
a first thermometer means for detecting the temperature of the fluid sample and producing a first output signal corresponding to the detected temperature of the fluid sample;
, ~, ~ .- , - - , :~ - .. ..
' ' ; '' ' , '' ' -, ~ :'' ' ' -~ a first controller for receiving the first output signal and an input command corresponding to a desired set point temperature of the fluid sample, determining a set point temperature of the liquid bath according to an operation formula expressed as a function of the difference between the desired set point temperature of the fluid sample and its detected temperature and producing a first controlled signal corresponding to the li~uid bath set point temperature determined by carrying out the operation formula;
a second thermometer means for detecting the temperature of the liquid bath and for producing a second output signal corresponding to the detected temperature of the liquid bath;
heating and cooling means for heating and cooling the liquid bath; and a second controller for receiving the second output signal and the first controlled signal and forming an actuating signal corresponding to the difference in level between the first controlled signal and the second output signal and subsequently inputting to the heating and cooling means a PID controlled signal formed on the basis of the actuatinq signal, the heating and cooling means being operative to heat and cool the liquid bath according to the PID controlled signal inputted thereto.
As clearly understood from the above-described :
construction and functions, the present temperature controlling means comprises a cascade control system. The first controller is provided with an operation circuit for calculating a timely suitable set point (which varies with time) of temperature of .
the thermostat in response to the detected temperature (which changes with time) of the fluid sample so that the fluid sample ~
..
-:- : . ~ :
1 3322q2 1 may be effectively heated or cooled by the thermostat,according to the detected temperature of the fluid sample, so as to speedily adjust the temperature of the fluid sample to its desired set point. The operation formula on which the operation circuit is based is expressed as a function of the difference between the set point of and the detected value of temperature of the fluid sample and the details thereof are experimentally determined according to the thermostat to be used, the kind of bath medium used therefor, the fluid sample container to be immersed in the medium and so forth. Moreover, the heating and cooling of the thermostat are effectively controlled according to a PID action formed in the second controller.
: .
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an external view of a thermostat for use in ~-viscosity measurement, which is provided with temperature controlling means embodylng the present invention;
FIG. 2 is an instrumentation flow sheet of temperature controlling means embodying the present invention;
FIG. 3 is a graph of an experimental result of controlling the temperatures of a medium bath and a fluid sample in accordance with the present invention; and FIG. 4 is a graph of an experimental result of heating and cooling the medium bath under the conditions that the set : .
, - : -~ ~ ' ' ' ' ' ':- ' ' :', - . :
. : : . :
,,:, .. ~ - : . - . . .. . . . :
1 point and the detected value of temperature of the fluid sample are directly fed back to a second controller in the present temperature controlling means without using a first controller in the present temperature controlling means.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring to FIG. 1, a fluid sample 3 whose viscosity is to be measured is received in a sample container 4 and immersed in a medium bath 8 of a thermostat 1. A viscosity sensor of a viscosity detector 2 and a temperature probe of a thermometer 11 are immersed in the fluid sample 3, where the viscosity detector 2 and the thermometer 11 are held by a stand 5. The temperature and viscosity of the fluid sample 3 detected by the detector 2 and the thermometer ll,respectively, are counted and displayed by a recorder 7. The recorder 7 makes an output signal corresponding to the detected temperature of the fluid sample 3 and inputs said signal into a temperature control device 6 of the thermostat 1. The control device 6 includes first and second controllers 13 and 17 which are described hereinafter. Also, reference numerals 18 and P designate heating and cooling means for the medium bath 8 and a pump for circulating the medium bath 8 to stir it.
- 6 - /cont. ...6a j?~
---` 1 3322q2 1 The temperature controlling means according to the present invention will be described with reference to FIG. 2.
The first thermometer 11 detects the temperature of the fluid sample 3, and a transmitter 12 attached to the first thermometer makes an output signal (hereinafter referred to as a first output signal) corresponding to the detected temperature of the fluid sample 3 and inputs the first output - 6a - /cont. ...7 .' .
:.~; . ~ , - . . :
1 signal into a first controller 13. As the first thermometer 11, a resistance thermometer composed of a platinum resistance wire or a thermistor or a thermocouple thermometer is preferably used. A predetermined set point of temperature of the fluid sample 3 is inputted in advance into the first controller 13 by an inputting means 14. The first controller 13 has an operation circuit which calculates a set point of temperature of the medium bath 8 according to an operation formula expressed as a function of difference between the predetermined set point of and the detected value (which changes with time) of the fluid sample temperature. The first controller 13 makes a controlled signal thereinafter referred to as a ~ :
first controlled signal) corresponding to the set point of the medium bath temperature calculated by the operation circuit and inputs the first controlled signal into a second controller 17. A second thermometer 15 detects the temperature of the medium bath 8, and a transmitter 16 attached thereto makes an output signal (hereinafter referred to as a second output signal) corresponding to the detected temperature of the medium bath 8 and inputs the second output signal into the second controller 17. The second controller 17 forms an actuating signal corresponding to the difference in level between the first controlled signal and the second output signal and makes a controlled signal (hereinafter referred to as a second controlled signal) formed on the basis of the actuating signal 1 332~q~
1 for a PID control of operation of heating and cooling means 18. The heating and cooling means 18 heats and cools the medium bath 8 in response to the second controlled signal. --It has been found to be preferable, as a result of a lot of experiment, that as the aforesaid operation formula for S calculating the set point of temperature of the medium bath 8, the following general expression is used in the present invention:
T~ = TS + Kp(Ts - MS(~ ~ KI (Ts ~
J-D
where T~ represents the set point of the medium bath temperature, TS represents the set point of the fluid sample temPeratUre' Ms(i) and Ms(j) the respective detected temperatures of the fluid sample at time i and i after starting the temperature controlling means to operate, Kp a proportional constant, KI an integral constant, and1~ a control period.
The values of Kp and KI are determined from the results of temperature control experiments which have been done upon preselection and preadoption of a thermostat, a bath medium, a fluid sample container and the like to be used. As understood from the above expression, the set point of the medium bath temperature to be fed back to the second controller 17 is changed with variation in the detected temperature of the fluid sample. ~
Next, a result of a temperature control experiment .
t 332292 carried out using the temperature controlling rneans in accordance with the present invention will be described with reference to FIG. 3. In FIG. 3, A designates the set point of temperature of a fluid sample, in which case the set point is 30C. B
denotes the detected temperature of the fluid sample, C the set point of a medium bath calculated by the aforementioned first controller, and D the detected temperature of the medium bath. The fluid sample used is an oil liquid. These temperatures A to D were pursued by a computer. As shown in FIG. 3, the temperature B of the fluid sample is adjusted to its set point A after about 35 minutes and then kept constant.
For comparison, FIG. 4 shows an experimental result when the operation of the heating and cooling means 18 is controlled according to a PID controlled signal formed, on the basis of the difference between the set lS point of and the detected value of temperature of a fluid sample, in the second controller 17. In this experiment, however, the first controller 13 is not used, and the signals of the set point and detected value of the fluid sample temperature are directly inputted into the second controller 17, where the detected temperature of a medium bath is not fed back to the second controller 17. As shown in FIG.
4, the temperature D of the medium bath repeatedly considerably fluctuates with time, and thereby the temperature 8 of the fluid sample also waves with a considerable delay of response and does not approach to its set point even after a lon~ time.
_ g _ ~ ~.
Claims (2)
1. Temperature controlling means for automatically controlling the temperature of a fluid sample for measuring viscosity of the fluid sample, said fluid sample being immersed in a liquid bath of a thermostat, said temperature controlling means comprising:
a first thermometer means for detecting the temperature of the fluid sample and producing a first output signal corresponding to the detected temperature of the fluid sample;
a first controller for receiving the first output signal and an input command corresponding to a desired set point temperature of the fluid sample, determining a set point temperature of the liquid bath according to an operation formula expressed as a function of the difference between the desired set point temperature of the fluid sample and its detected temperature and producing a first controlled signal corresponding to the liquid bath set point temperature determined by carrying out the operation formula;
a second thermometer means for detecting the temperature of the liquid bath and for producing a second output signal corresponding to the detected temperature of the liquid bath;
heating and cooling means for heating and cooling the liquid bath; and a second controller for receiving the second output signal and the first controlled signal and forming an actuating signal corresponding to the difference in level between the first controlled signal and the second output signal and subsequently inputting to the heating and cooling means a PID
controlled signal formed on the basis of the actuating signal, the heating and cooling means being operative to heat and cool the liquid bath according to the PID controlled signal inputted thereto.
a first thermometer means for detecting the temperature of the fluid sample and producing a first output signal corresponding to the detected temperature of the fluid sample;
a first controller for receiving the first output signal and an input command corresponding to a desired set point temperature of the fluid sample, determining a set point temperature of the liquid bath according to an operation formula expressed as a function of the difference between the desired set point temperature of the fluid sample and its detected temperature and producing a first controlled signal corresponding to the liquid bath set point temperature determined by carrying out the operation formula;
a second thermometer means for detecting the temperature of the liquid bath and for producing a second output signal corresponding to the detected temperature of the liquid bath;
heating and cooling means for heating and cooling the liquid bath; and a second controller for receiving the second output signal and the first controlled signal and forming an actuating signal corresponding to the difference in level between the first controlled signal and the second output signal and subsequently inputting to the heating and cooling means a PID
controlled signal formed on the basis of the actuating signal, the heating and cooling means being operative to heat and cool the liquid bath according to the PID controlled signal inputted thereto.
2. The temperature controlling means according to claim 1, wherein the operation formula comprises:
Tb = Ts + Kp(Ts - Ms(i)) + ? Kl.SIGMA.?j = 0 (Ts - Ms(j)) wherein:
Tb = the set point temperature of the liquid bath;
Ts = the desired set point temperature of the fluid sample;
? = a control period;
Ms(i) and Ms(j) are the detected temperature of the fluid sample at times i and j after starting the temperature controlling means to operate;
Kp = a proportional constant; and Kl = an integral constant.
Tb = Ts + Kp(Ts - Ms(i)) + ? Kl.SIGMA.?j = 0 (Ts - Ms(j)) wherein:
Tb = the set point temperature of the liquid bath;
Ts = the desired set point temperature of the fluid sample;
? = a control period;
Ms(i) and Ms(j) are the detected temperature of the fluid sample at times i and j after starting the temperature controlling means to operate;
Kp = a proportional constant; and Kl = an integral constant.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000589963A CA1332292C (en) | 1989-02-02 | 1989-02-02 | Temperature controlling means for a thermostat for use in measuring viscosity |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000589963A CA1332292C (en) | 1989-02-02 | 1989-02-02 | Temperature controlling means for a thermostat for use in measuring viscosity |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1332292C true CA1332292C (en) | 1994-10-11 |
Family
ID=4139567
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000589963A Expired - Fee Related CA1332292C (en) | 1989-02-02 | 1989-02-02 | Temperature controlling means for a thermostat for use in measuring viscosity |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1332292C (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102489354A (en) * | 2011-11-30 | 2012-06-13 | 盛司潼 | System for controlling constant temperature metal bath and method thereof |
| EP2965060A4 (en) * | 2013-03-07 | 2016-10-19 | Cambridge Viscosity Inc | Viscosity measurement of liquids at subambient temperatures |
-
1989
- 1989-02-02 CA CA000589963A patent/CA1332292C/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102489354A (en) * | 2011-11-30 | 2012-06-13 | 盛司潼 | System for controlling constant temperature metal bath and method thereof |
| CN102489354B (en) * | 2011-11-30 | 2014-05-28 | 盛司潼 | System for controlling constant temperature metal bath and method thereof |
| EP2965060A4 (en) * | 2013-03-07 | 2016-10-19 | Cambridge Viscosity Inc | Viscosity measurement of liquids at subambient temperatures |
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