EP1595134A1 - Method and instrument for measuring surface tension - Google Patents
Method and instrument for measuring surface tensionInfo
- Publication number
- EP1595134A1 EP1595134A1 EP04709393A EP04709393A EP1595134A1 EP 1595134 A1 EP1595134 A1 EP 1595134A1 EP 04709393 A EP04709393 A EP 04709393A EP 04709393 A EP04709393 A EP 04709393A EP 1595134 A1 EP1595134 A1 EP 1595134A1
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- Prior art keywords
- liquid
- capillary
- drops
- fluid
- drop
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N13/00—Investigating surface or boundary effects, e.g. wetting power; Investigating diffusion effects; Analysing materials by determining surface, boundary, or diffusion effects
- G01N13/02—Investigating surface tension of liquids
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N13/00—Investigating surface or boundary effects, e.g. wetting power; Investigating diffusion effects; Analysing materials by determining surface, boundary, or diffusion effects
- G01N13/02—Investigating surface tension of liquids
- G01N2013/0241—Investigating surface tension of liquids bubble, pendant drop, sessile drop methods
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- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Measuring Fluid Pressure (AREA)
Abstract
In measuring the surface tension between a liquid and fluid such as a gas, a capillary (3, 3') is used in which the liquid is slowly flowing and at the end of which drop (11) are formed and fall off inside a closed space (7) containing the fluid. Using a measurement device (5, 5'), that for example can be of optical nature, the times are measured when a drop reaches a predetermined size and when a drop falls off. The time period from the time when a drop has reached a predetermined size until it falls off and the time period until the next drop reaches the predetermined size are used for calculating the surface tension of the liquid. The measurement can be made rather rapidly and with a high operational reliability and is relatively little influenced by variations in the feeding velocity for the fluid. The temperature difference between the drop and the surrounding fluid is small, this causing a small precipitation of salts dissolved in the liquid and reducing the risk of blocking the liquid capillary. A pump (31) connected to the outlet (9) of the closed space (7) produces a subatmospheric pressure in the fluid in the closed space and hence makes liquid flow up to the end of the capillary to there form the drops (11). Since the fluid in the closed space (7) is compressible, it will attenuate possible pulsations and interference derived from the pump (31), so that they do not affect the growth and falling-off of the drops (11). The attenuation of pulses allows the use of a simpler, more robust and more industrially resistant pump to achieve the required liquid flow through the capillary (3).
Description
METHOD AND INSTRUMENT FOR MEASURING SURFACE TENSION RELATED APPLICATION
This application claims priority and benefit from Swedish patent application No. 0300329- 0, filed February 7, 2003, the entire teachings of which are incorporated herein by reference. TECHNICAL FIELD
The present invention relates to a method and an instrument for measuring surface tension by detecting liquid drops formed at the end of a capillary. BACKGROUND
For many different processes it is of great importance to know the size of the surface tension of a liquid. The surface tension can indicate the substances existing in the liquid and the concentrations thereof. By continuously measuring the surface tension, either dynamically or statically, a possibility of analyzing a liquid is provided. The analysis can then be used to for example control the concentrations of different substances in the liquid.
A problem existing today is that it is not possible to continuously measure surface tension in a dynamical and exact way. The conventionally used methods for measuring surface tension are based on an external analysis of the surface tension, i.e. that a sample must be taken from the system in order for an analysis thereof will be performed. This method results in that there long time has to pass before an answer can be obtained. The disadvantages of such methods are naturally plural, and thereamong the following can be mentioned: - Time consumption. Because of the fact that it is not possible to perform the measurement inside the process it takes a longer time.
- No possibility of obtaining an immediate answer. In many cases it means that one has to wait for up to a week for the answer to the question whether for example a correct tenside concentration exists in a process bath. In some cases the manufacturing company must place the products already manufactured in quarantine waiting for results of the analysis. In the case of a negative outcome all that has been already produced must be reprocessed or in the worst case be completely discarded.
- Requirement of manually labor. Today manually labor is required in using all existing methods.
- No possibility of dynamical feedback. Since it is not possible to control these processes dynamically in a feedback manner the possibility of arranging a continuous control of the contents of different substances in the processes is lost.
In the article Nels A. Olson, Robert E. Synovec, William B. Bond, Dana M. Alloway, Kristen Skogerboe, "Dynamic Surface Tension and Adhesion Detection for the Rapid Analysis of Surfactants in Flowing Aqueous Liquids", Anal. Chem. 1987, Vol. 69, pp. 3496 - 3505, a method is
described for measuring surface tension. Drops are formed from a liquid flow through a capillary at the end of the capillary in contact with the surrounding air and the pressure in the liquid is measured during the forming and the release of the drops from the end of the capillary. The pressure is measured by a differential pressure sensor connected both to the capillary and to the surrounding air. This method has disadvantages. For example, a temperature difference can exist between the drops and the surrounding air or gas, this possibly implying precipitation of salts that can plug or block the capillary.
Similar methods for measuring surface tension are described in the articles C.A. MacLeod, C.J. Radke, "A Growing Drop Technique for Measuring Dynamic Interfacial Tension", Journal of Colloid and Interface Science, 1993, Vol. 160, pp. 435 - 448, and Keith E. Miller, Emilia Bramanti, Bryan J. Prazen, Marina Prezhdo, Kristen J. Skogerboe, Robert E. Synovec, "Multidimensional Analysis of Poly(ethylen glycols) by Size Exclusion Chromotography and Dynamic Surface Tension Detection", Anal. Chem., 2000, Vol. 72, pp. 4372 - 4380.
In U.S. patent 4,942,760 a device for measuring surface tension is disclosed, in particularly for measuring on liquids under relatively high pressures and temperatures. Liquid is injected with a high pressure from a cylinder pump into a closed space in which, by a camera, a picture is captured of a formed drop. Using this device the surface tension cannot be determined continuously or periodically at repeated small time intervals. Therefore it is not suited for for example process control. In U.S. patent 4,646,562 a method is disclosed for continuously monitoring surface activity and surface tension of a liquid. The time intervals between the times when drops fall off from a nozzle are measured and evaluated. In the method disclosed in the published International patent application WO03/014707, assigned to the same part as the present invention and incorporated by reference herein, drops are formed at the end of a capillary in a closed space. The pressure in the closed space or the difference between this pressure and the pressure in the capillary is measured and evaluated to determine the surface tension.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method and a measurement instrument for measuring surface tension with a high operational security.
It is another object of the invention to provide a method and a measurement instrument for measuring surface tension using a capillary, at the end of which drops are formed.
It is another object of the invention to provide a method and a measurement instrument for measuring surface tension using a capillary, at the end of which drops are formed, in which method and instrument a reduced precipitation of salt exists, and hence a lower risk of plugging.
It is another object of the invention to provide a method and a measurement instrument for measuring surface tension based on detecting liquid drops formed at the end of a capillary.
It is another object of the invention to provide a method for measuring surface tension including a capillary at the ends of which drops are formed and a device for detecting liquid drops, in which a possible blocking of the capillary can be eliminated in a relatively simple way.
It Is another object of the invention to provide a method and a measurement instrument for measuring surface tension that are suited to provide new or current measurement values in a relatively continuous manner, i.e. with relatively short time intervals.
It is another object of the invention to provide a method and a measurement instrument for measuring surface tension in which measured values are not significantly influenced by pulsations derived from pumps.
It is another object of the invention to provide a method and a measurement instrument for measuring surface tension, in which measured values are not significantly influenced by variations of the flow velocity of the liquid, the surface tension of which is determined. In a method and an instrument for detecting surface tension or interfacial tension, dynamically as well as statically, between a liquid and a fluid such as a gas a capillary is used, in which a liquid is slowly flowing and at the end of which drops of the liquid are formed and fall off. The point of the capillary is located inside a closed space containing the fluid so that the drops fall off in this space. Using a suitable device for detecting growth and/or release of liquid drops a measured signal is generated. This detecting device can include an electrical sensor, an acoustical sensor or preferably an optical sensor.
In the closed space containing the fluid advantageously a sub-atmospheric pressure is maintained by pumping liquid away from the closed space. The difference between the sub-atmospheric pressure and the ambient pressure that can be relatively small causes new liquid to flow to the point of the capillary. A suction pump is then connected to the closed space, to a liquid outlet thereof, in order to transport the liquid away. The fluid or gas contained in the closed space thereby separates in nearly mechanical manner a liquid drop at the end of the capillary from the liquid sucked away by the pump. Vibrations, pulsations and other interference derived from the pump when it is operating will therefore not significantly influence the liquid drop or at least such vibrations, pulsations and interference during the time period when the liquid drop is being formed, is growing and finally falls off are strongly reduced. Also, the liquid flow in the capillary is not significantly affected. The fluid or gas in the closed space then works as a pulse attenuator. Told in another way, the flow velocity of the liquid in the supply conduit fluctuates less during each drop forming period compared to known
methods. It implies that the simple pump having a pulsating flow behavior can be used, this allowing the use of low cost and/or industrially reliable and robust pumps. Due to the fact that liquid drops are formed in a closed space also, if desired, the velocity of the liquid flow though the capillary up to the point thereof at which the drops are formed can be controlled by varying the sub-atmo- spheric pressure generated by the pump.
The sensor used in the detection of the growth and falling off of liquid drops is advantageously designed to detect two positions, a first position when a liquid drop during its growth at the end of the capillary reaches a given or predeteπnined size, and a second position when the drops falls off from the end of the capillary. Thus, the time periods which are measured between the reaching of the second positions, i.e. the times when a plurality of successive liquid drops fall off from the point or outlet of the capillary, are divided in two portions by also measuring the times when the first positions is reached. The relationship or quotient between the lengths of these two portions of the time periods can be used for calculating the surface tension of the liquid. Told in another way, the time periods for the growth of a plurality of successively drops are each measured and are, due to another measurement for each drop, divided in two sub-periods. It appears that the measured value of the surface tension of a liquid calculated from these two time lengths is not significantly negatively affected by unintended and unknown changes of the flow velocity of the liquid when it is being fed to the closed space, i.e. the flow velocity inside the capillary.
An optical sensor for using the measurements of the liquid drops can for example include a photosensitive cell, a photosensitive switch, an optical distance meter, an photo-electric cell device consisting of a light source together with an associated sensor, a light absorbance meter consisting of a light source together with an associated sensor, a refraction meter consisting of a light source together with an associated sensor, a reflection meter consisting of a light source together with an associated sensor, an optical thermal sensor or a picture sensor provided to form an image or picture of the growth and falling off of drops.
An electrical sensor can for example include an electrostatic contact sensor, a conductive sensor, an inductive sensor, a permeability sensor, a capacity sensor or a magnetic sensor. An acoustic sensor can for example include a sound distance meter.
Advantageously the signal is evaluated during a longer time period comprising one or more cycles which each one includes that a drop is being formed and that it falls off from the end of the capillary to give a value of the surface tension.
The method and instrument are thus based on the detection of growth and/or falling off of liquid drops from an end of a capillary. Due to the fact that the drops for which a detection is made
are formed in a fluid trapped in a closed space or volume, a high operational security is obtained.
The temperature difference between a liquid drop during the formation and growth thereof and the surrounding fluid becomes smaller, this causing a low degree of precipitation of salts dissolved in the liquid. The risk of the liquid capillary being blocked is thereby reduced. If the capillary at the point of which the drops are formed and falls off, still and in spπe of what can be expected, would be blocked, the sub-atmospheric pressure created by the suction r Limp in the fluid surrounding the drop will assist to restart the liquid flow through the capillary.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the methods, processes, instrumentalities and combinations particularly pointed out in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
While the novel features of the invention are set forth with particularly in the appended claims, a complete understanding of the invention, both as to organization and content, and of the above and other features thereof may be gained from and the invention will be better appreciated from a consideration of the following detailed description of non-limiting embodiments presented hereinbelow with reference to the accompanying drawings, in which:
- Fig. 1 is a schematic view of the central parts of a measurement instrument, based on a photo- electric cell device, for measuring the surface tension of a liquid by detecting two positions in the growth and falling off of liquid drops at the end of a capillary inside a closed space connected to a suction pump,
- Fig. 2a is a diagram showing the measured signal as a function of time when a plurality of dr.ips are successively being formed at the end of a capillary and during the growth and falling off thereof pass a photo-electric cell device consisting of a light source together with an associated sensor,
- Figs. 2b - 2e are schematic pictures illustrating the growth and falling off of drops at the end c f a capillary in four different positions,
- Figs. 3a and 3b are diagrams showing the flow velocity as a function of time through a suction pump and through a capillary, respectively, liquid drops being formed and falling off at the end of the capillary,
- Fig. 4 is a block diagram of a measurement instrument for measuring surface tension, and
- Fig. 5 is a block diagram of an alternative embodiment of a measurement instrument for measur-
ing surface tension.
DETAILED DESCRIPTION
In Fig. 1 are shown the central parts of an assembly or installation or measurement instrument for detecting or measuring surface tension, dynamically as well as statically between a liquid and a gas by detecting two positions in the growth and falling off of liquid drops at the end of a capillary, or generally between a first liquid having a higher, generally a considerably higher, density and a second fluid having a lower density that can be gas or liquid. The liquid, the surface tension of which in relation to the fluid is to be measured, is supplied with a substantially constant flow velocity from a source, not shown in this figure, through a capillary 3 into a chamber 7. The capillary has at its free end portion an end surface at which drops of the liquid are being formed and from which they fall off. The end surface can for example advantageously be located horizontally whereas the end portion can extend in a vertical direction, as has been indicated above. In the chamber 7 there is normally some amount of the supplied liquid and the fluid, in relation to which one desires to measure the surface tension of the liquid. A pump 31 sucks liquid away from the chamber 7 and creates in that way a sub-atmospheric pressure for the fluid contained in the chamber 7. It forces liquid to flow through the capillary 3 and to form, at the mouth of the capillary, drops 11 which one after another falls down towards the bottom of the chamber 7. In order that it will possible to obtain a reliable value of the surface tension of a liquid by studying a drop that is growing and falls off it is tremendously important that the drop is not influenced by any mechanical interference of any kind. Thus, one would have to put tremendously high requirements on the pulsation freedom of a pump in order to use it to press liquid into the capillary 3, at the end of which drops are formed and fall off.
By arranging and using, in the illustrated way, the suction pump 31 at the outlet of the chamber 7, the drop 11 at the end of the capillary 3 is, because of the fluid trapped in the chamber 7, completely mechanically separated from the pump 31 in the case where the fluid is a compressible gas. This mechanical separation implies that possible pulsations and fluctuations in the flow through the pump 31, are prevented from interfering with the drop 11. This attenuation of pulsations is among other things necessary to allow the use of industrially suited and chemically resistant pumps, for example hose pumps. Then, the signal recorded by the photo-electric cell device 5, 5' will vary periodically, see the description hereinafter. The signal from the photo-electric cell device 5, 5' is recorded for two or advantageously several periods, i.e. for a plurality of drops that have fallen down, and is evaluated in an evaluation device 12, suitably a computer or microprocessor.
The photo-electric cell device 5, 5' is placed so that it can detect the drop at the end of the capillary 3, when it has a size sufficient to break the light ray of the photo-electric cell device 5, 5'. The light ray of the photo-electric cell device 5, 5' will thus be broken from the time when the drop reaches some size until it falls off. Thereupon, the light ray of the photo-electric cell device 5, 5' will be unbroken until the next drop reaches the size when it breaks the light ray of the photo-electric cell device 5, 5'. From this signal the surface tension can be derived using calculations performed for example by the evaluation device 12.
The unbroken drop time to which is defined as the time that it takes from the time that a drop 11 falls off from the end of the capillary 3 until the next drop 11 breaks the light ray of the photo-electric cell device 5, 5' is calculated. Also broken drop time tb which is defined as the time period that it takes from the time when a drop 11 breaks the light ray of the photo-electric cell device 5, 5' until the time when the drops falls off from the end of the capillary 3 is calculated.
These time periods are functions of the size of the capillary, the velocity with which liquid is flowing to the capillary opening, the viscosities and densities of the liquid and the fluid and the dynamical surface tension γdyn between the liquid forming drops and the fluid in which the drops are being formed.
Assuming that the drops are slowly formed and that the liquid has a low viscosity, the influence of the viscosity on these times can be considered to be negligible. If the density of the liquid can be considered to be constant, the influence of the density thus does not have to be considered. The fluid in the system is assumed to be the same one over time and also the diameter of the capillary, at the end of which the drops are formed. Remaining factors influencing these measured times are the flow velocity and the dynamical surface tension between the liquid and the fluid.
Due to the fact that changes in the flow velocity influences the two times to and tb in a similar way it is possible to minimize, by using as a departing point for the calculation of the surface tension a relationship or quotient between theses times, the influence that variations of the flow velocity through the capillary can have on the measurement result.
For these assumptions, for example the following simplified assumption can be allowed:
Q = t0 / (tb + to)kι
Ydyn = 2 - Q2 + k3 - Q + k4
where Q is a function by means of which the dependence of to and of t on the flow velocity has
been eliminated. Thus, using these simplified assumptions the values of the constants ki, k2, k3 and k4 can be determined by a calibration method using three liquids having known surface tensions and having viscosities and densities of the same magnitude of order as those of the liquid that will later be investigated. Thereupon the surface tension of the desired liquid can be deter- 5 mined using a measurement instrument according to Fig. 1.
Using the measurement instrument according to Fig. 1 a measured signal is obtained similar to that illustrated in Fig. 2a. From the signal the surface tension can be determined in the same way as been described above by a calibrating method using liquids having known characteristics. In Fig. 2b a drop is schematically shown that has not yet had time to break the ray path 0 between the parts of the photo-electric cell device 5, 5'. In Fig. 2c a drop is illustrated that precisely breaks the ray path of the photo-electric cell device 5, 5'. In Fig. 2d a drop is illustrated when it continues to grow while the ray path of the photo-electric cell device 5, 5' is broken. In Fig. 2e a drop is illustrated that falls off and hence stops to break the ray path of the photo-electric cell device 5, 5'. 5 In Fig. 3 a an example of the flow velocity as a function of time for the flow through the pump 31 is shown. In Fig. 3b the corresponding flow velocity as a function of time for the flow through the capillary is shown, in the case where the fluid 7 is a compressible gas, which mechanically separates or isolates the pump 31 from the capillary 3 and in that way acts as a pulse attenuator between them. 0 A measurement instrument or measurement installation based on the method described above with reference to Fig. 1 can for example be designed as illustrated in the block diagram of Fig. 4. A pump 13 pumps liquid, for which a measurement is to be made, from a monitored bath 15 containing liquid to a container or a reservoir 17 placed on a horizontal level above that of the chamber 7. In the reservoir 17 the upper surface of the liquid always has a constant height which 25 is achieved using some kind overflow device such as a spillway. The spillway overflow includes a partition wall 19 in the reservoir 17 which divides it in a first chamber 21 filled with liquid up to the upper edge of the partition wall and a second chamber 23. The second chamber has a bottom outlet, which by a conduit 25 returns overflowed liquid to the monitored bath 15. The first chamber 21 has also a bottom outlet, which through a conduit 21 including a first controlled valve 30 29 that is connected therein and is the on/off type, is connected to the inlet conduit for liquid to the capillary 3.
Furthermore, the second pump 31 is connected to the outlet 9 of the chamber 7. Also, an aerating connection 4 is provided that is connected to a first end of a second valve 37 of on/off
type, the other end of which is open to the ambient air. Flow meters 32 and 33 are arranged in the supply conduit to the capillary 3 and in the outlet conduit from the closed space 7, respectively.
When using the installation according to Fig. 4 for measuring surface tension the valves have the positions illustrated. The first valve 29 is then in such a position that liquid is supplied to
5 the inlet of the chamber 7. The second valve 37 is set so that the chamber 7 is completely separated from the surrounding air. When starting the installation the first valve 29 is set to stop the supply of liquid to the capillary 3 and the second valve 37 is opened to connect the chamber to the surroundings. Thereby, the pump 31 empties the chamber 7 from possible liquid remaining from an earlier measurement. Thereupon, the valves 29, 37 are set to their opposite positions and o then the instrument is ready to provide measurement data.
Blocking of the capillary 3 is avoided by the weak sub-atmospheric pressure in the chamber 7 created by the pump 31. The pumping velocity of this pump can be set so that a substantially constant liquid flow to the chamber 7 is obtained and hence a constant volume of the fluid trapped in the chamber 7 is obtained in the case where it is compressible. 5 In a practical embodiment according to Fig. 5, the photo-electric cell device 5 was of IR- type, the model 303 from the company Omron. It was supplied with a voltage of 24 V DC and provided a signal of 0 - 19 V. The chamber 7 had an inner volume of 16.5 ml. The signal from the sensor 5 was provided to electronic circuits, compare the evaluation unit 12 in Fig. 1, comprising a 12-bit A/D-converter, of the type ADS7816 from the company Burr-Brown, controlled by a 0 microprocessor of type ATmegal03 from the company Atmel, operating at a clock frequency of 3.6864 MHz. In the installation two hose pumps 47, 49 were included, each having two channels and manufactured by the company Watson Marlow Alitea and particularly designed to fulfill the requirements of the measurement installation. A first side of the first hose pump 47 was used to pump liquid from the monitored bath 15 to a cross flow filter 51, from which a larger amount of 5 liquid was returned to the bath by being conducted to the second chamber 23 in the reservoir 17, whereas a smaller amount, pumped by the first side of the second pump 49, was supplied to the first chamber 21. The second side of the first pump was used to pump liquid from the second chamber 21 in the reservoir to the monitored bath. The second side or channel of the second pump 49 replaces the suction pump 31 in the embodiment of Fig. 4 and pumps liquid from the 0 closed space 7 to the second chamber in the reservoir 17. This channel or side of the second hose pump 49 caused a flow of approximately 1 ml liquid per minute through the chamber.
While specific embodiments of the invention have been illustrated and described herein, it is realized that numerous additional advantages, modifications and changes will readily occur to
those skilled in the art. Therefore, the invention in its broader aspects is not limiteri o the specific details, representative devices and illustrated examples shown and described herein ; Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. It is t terefore to be understood that the appended claims are intended to cover all such modifications aαd changes as fall within a true spirit and scope of the invention.
Claims
1. A method for measuring surface tension at the interface between a liquid and a fluid, hi particular a gas, the liquid having a density higher than that of the fluid and being a substantially unmiscible therewith, and the method including that the liquid is formed to flow through a capillary for forming drops at an end of the capillary, characterized in
- that in the step of making the liquid flow through the capillary the drops are formed in a closed space containing the fluid,
- that the liquid is made to flow through the capillary substantially only by the fact that the liquid is continuously pumped away from the closed space to thereby create a sub-atmospheric pressure in the closed space and cause that new drops are formed at the end of the capillary,
- that growth and/or falling off of liquid drops from the end of the capillary are detected, and
- that the detected signal is evaluated.
2. A method according to claim 1 , characterized in the detection of growth and/or falling off of liquid drops from the end of the capillary is made by measuring or sensing the position and/or movement of the drops.
3. A method according to any of claims 1 - 2, characterized in that the flow velocity is measured of the liquid flowing to form drops at the end of the capillary and/or of the liquid that flows away from the closed space.
4. A method according to any of claims 1 - 3, characterized in that growth and/or falling off of liquid drops from the end of the capillary are detected optically, in particularly using optical imaging.
5. A method according to any of claims 1 - 3, characterized in that growth and/or falling off of liquid drops from the end of the capillary is detected acoustically or electrically.
6. An instrument for measuring surface tension at the interface between a liquid and a fluid, preferably a gas, the liquid having a density higher than that of the fluid and being substantially unmiscible therewith, the mstrument including:
- a supply device for the liquid to supply it at substantially the ambient pressure,
- a capillary connected to the supply device and having a first end so that the liquid is made to flow through the capillary for forming drops at the first end of the capillary, characterized by
- a closed space to which the first end of the capillary is connected and which contains the fluid,
- a pump arranged to continuously suck liquid away from the closed space to thereby cause that new drops are formed at the end of the capillary, - a device for detecting growth and/or falling off of liquid drops from the end of the capillary, and
- an evaluation device connected to the detection device for evaluating the signal provided therefrom.
7. An instrument according to claim 6, characterized in that the device for detecting growth and/or falling off of liquid drops from the end of the capillary makes the detection by measuring or directly sensing the position and/or movement of the drops.
8. An instrument according to any of claims 6 - 7, characterized in that the pump pumps with a known flow velocity.
9. An instrument according to any of claims 6 - 8, characterized by a device for measuring the flow velocity of the liquid that is flowing for forming drops at the end of the capillary and/or a device for measuring the flow velocity of the liquid that is flowing away from the closed space.
10. An instrument according to any claims 6 - 9, characterized in that the device for detecting growth and/or falling off of liquid drops from the end of the capillary includes a light source and a photosensitive cell arranged, so that a falling drop breaks a light beam emitted from the light source towards the photosensitive cell.
11. An instrument according to any of claims 6 - 9, characterized in that the device for detecting growth and or falling off of liquid drops from the end of the capillary includes an optical image sensor, on the light sensitive surface of which drops staying in the vision field thereof are imaged.
12. An instrument according to any of claims 6 - 9, characterized in that the device for detecting growth and/or falling off of liquid drops from the end of the capillary includes an acoustic sensor, in particularly a sound distance meter, or an electric sensor, in particularly a conductive sensor, an inductive sensor, a permeability sensor, a capacitive sensor or a magnetic sensor.
13. An instrument according to any of claims 6 - 12, characterized in that the supply device includes a liquid reservoir having an upper liquid surface located at a constant horizontal level above the level of the inlet of the capillary, whereby the liquid is supplied with a substantially free flow up to and through the capillary.
14. A method for measuring surface tension at the interface between a liquid and a fluid, in particular a gas, the liquid having a density higher than that of the fluid and being substantially unmiscible therewith, the method including that the liquid is forced to flow through a capillary for forming drops at the end of the capillary, characterized in - that in the step of making the liquid flow through the capillary the drops are formed in a closed space containing the fluid,
- that growth and/or falling off of liquid drops from the end of the capillary are detected by deterrriining times for two characteristic positions or states of the drop at the formation and falling off of the drop, in particularly the times, when a drop reaches a predetermined size and when a drop falls off,
- that from these determined times the time lengths or intervals between them are calculated, and
- that the calculated values are evaluated.
15. A method according to claim 14, characterized in that in the step of making the liquid flow through the capillary, liquid is continuously sucked away from the closed space to thereby cause new drops to be fomied.
16. A method according to any of claims 14 - 15, characterized in that in the step of making the liquid flow through the capillary, the liquid is supplied with a free flow from a liquid reservoir having an upper liquid surface located at a constant horizontal level above the level of the inlet to the capillary.
17. A method according to any of claims 14 - 16, characterized in that growth and/or falling off of liquid drops from the end of the capillary are detected optically, acoustically or electrically.
18. An instrument for measuring surface tension at the interface between a liquid and a fluid, preferably a gas, the liquid having a density higher than that of the fluid and being substantially unmiscible therewith, the instrument including:
- a supply device for supplying the liquid,
- a capillary connected to the supply device and having a first end so that the liquid is made to flow through the capillary for forming drops at the first end of the capillary, characterized by - a closed space to which the first end of the capillary is connected and which contains the fluid,
- a device for detecting growth and/or falling off of liquid drops from the end of the capillary arranged to determined times for two characteristics positions or states of the liquid drop in the formation thereof and in the falling off of the drop, in particularly the times when a liquid drop has reached a predetermined size and when a drop falls off, and - an evaluation device connected to the detection device for calculating from the output signal thereof the time lengths or lengths of the intervals between the determined times and evaluating these lengths.
19. An instrument according to claim 18, characterized by a pump connected to the closed space and arranged to continuously suck liquid away from the closed space to thereby cause new drops to be formed at the end of the capillary.
20. An instrument according to any of claims 18 - 19, characterized in that the supply device includes a liquid reservoir having an upper liquid surface located at a constant horizontal level above the level of the inlet to the capillary, whereby the liquid is supplied with a substantially free flow to and through the capillary.
21. An instrument according to any of claims 18 - 20, characterized in that the device for detecting includes an optical, acoustical or electric sensor.
1/3
Fig. 2a
Signal t
LΠ JΠJΠ_ tΓLΓLΠ
Time
Fig. 2b Fig. 2c Fig. 2d Fig. 2e
3/3
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE0300329 | 2003-02-07 | ||
| SE0300329A SE0300329D0 (en) | 2003-02-07 | 2003-02-07 | Procedures and instruments for measuring surface tension |
| PCT/SE2004/000169 WO2004070360A1 (en) | 2003-02-07 | 2004-02-09 | Method and instrument for measuring surface tension |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| EP1595134A1 true EP1595134A1 (en) | 2005-11-16 |
Family
ID=20290337
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP04709393A Withdrawn EP1595134A1 (en) | 2003-02-07 | 2004-02-09 | Method and instrument for measuring surface tension |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP1595134A1 (en) |
| SE (1) | SE0300329D0 (en) |
| WO (1) | WO2004070360A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112255145A (en) * | 2020-10-09 | 2021-01-22 | 江苏东科新能源材料有限公司 | Method for high-precision and rapid test of dyne value of substrate surface |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1950550A1 (en) * | 2007-01-25 | 2008-07-30 | Flamac | Method and apparatus for measuring viscosity and surface tension |
| CN104596894A (en) * | 2015-01-28 | 2015-05-06 | 淮阴师范学院 | Spiral adjustable constant-temperature device for measuring surface tension of liquid and electricity measurement and control method thereof |
| CN106004044B (en) * | 2016-05-11 | 2017-12-22 | 京东方科技集团股份有限公司 | Ink measuring system and printing device |
| JP2018163016A (en) * | 2017-03-24 | 2018-10-18 | 東芝テック株式会社 | Droplet dispensing device |
| CN112945805B (en) * | 2021-01-28 | 2022-04-05 | 哈尔滨工程大学 | Microstructure fiber grating series connection device and liquid density measurement method |
| CN113670776B (en) * | 2021-07-29 | 2023-12-05 | 杭州电子科技大学 | Liquid drop surface tension measuring method adopting multistage ellipse fitting |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2937476A1 (en) * | 1979-09-17 | 1981-04-02 | Agfa-Gevaert Ag, 5090 Leverkusen | DEVICE FOR MEASURING THE SURFACE TENSION |
| DE3125864A1 (en) * | 1981-07-01 | 1983-01-20 | Bayer Ag, 5090 Leverkusen | Apparatus for measuring the surface tension using the stalagmometer principle |
| US4646562A (en) * | 1984-10-30 | 1987-03-03 | Miller Brewing Company | Method and apparatus for detecting relative dynamic liquid surface activity |
| US4942760A (en) * | 1989-03-28 | 1990-07-24 | Intevep, S.A. | Apparatus for the measurement of interfacial tension |
| SE519771C2 (en) * | 2001-08-10 | 2003-04-08 | Jenser Technology Ab | Measuring method for surface tension at interface surface between a liquid and a fluid, in particular a gas, liquid having larger density than fluid, measuring pressure of fluid in closed space in which drops are formed |
-
2003
- 2003-02-07 SE SE0300329A patent/SE0300329D0/en unknown
-
2004
- 2004-02-09 EP EP04709393A patent/EP1595134A1/en not_active Withdrawn
- 2004-02-09 WO PCT/SE2004/000169 patent/WO2004070360A1/en active Application Filing
Non-Patent Citations (1)
| Title |
|---|
| See references of WO2004070360A1 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112255145A (en) * | 2020-10-09 | 2021-01-22 | 江苏东科新能源材料有限公司 | Method for high-precision and rapid test of dyne value of substrate surface |
| CN112255145B (en) * | 2020-10-09 | 2024-03-12 | 江苏东科新能源材料有限公司 | Method for rapidly testing surface dyne value of substrate with high precision |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2004070360A1 (en) | 2004-08-19 |
| SE0300329D0 (en) | 2003-02-07 |
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