CZ25212U1 - Levitation-vibrating device for measuring viscosity, density and interfacial tension - Google Patents

Description

Levitation-vibration device for measuring viscosity, density and surface tension

Field of technology

Measurement of theological properties of fluids, equipment for measuring viscosity, density and surface tension.

State of the art

Current methods of measuring the Theological properties of fluids are based on the registration of quantities that are functionally related to these properties in a certain way.

Viscosity is measured with viscometers or rheometers. They can be divided into capillary (flow), discharge, body (gravitational), rotary, vibrational and torsional, according to other criteria stationary and non-stationary.

In practice, simple geometry viscometers are used for common Newtonian fluids. Here we can mention, for example, the Ubbelohde discharge viscometer. These viscometers are usually used for indicative measurement of viscosities in technical practice. Other widely used viscometers are rotary. They require a complex design to achieve proper accuracy, however, they have some advantages over discharge viscometers: easy change of shear stress or shear rate, easy setting of measurement time, liquid does not flow. These viscometers can also be applied to Newtonian fluids and perform precise laboratory experiments with them. Their disadvantage is the previously mentioned construction complexity and associated production costs. Nevertheless, this type of viscometers is the most common in current industrial practice requiring accurate registration of the Theological properties of liquids. There are many of them on the market. Vibrating viscometers have a related design. These are currently less common, although they offer relatively high accuracy of measured data. The Hoppler viscometer can also be found to a lesser extent in laboratory practice. Piezoelectric string viscometers are more of a rare design.

Surface tension is usually measured with strain gauges, which are used to measure various droplet parameters. For example, the Wilhelmi plate tensiometer uses plates immersed in a liquid that measures the force required to pull it out. The surface tension value is then calculated from the measured value. Another type is a ring tensiometer according to Du Noy, which uses a platinum ring immersed in a liquid, which measures the voltage that needs to be developed to pull it out. The surface tension value is then calculated from the measured value. The closest of the present solution is probably a Du Noah - Padday bar tensiometer, which uses a bar immersed in a liquid, measuring the force that must be exerted when pulling the bar out of the liquid. Capillary staglamometers can also be found to a limited extent.

Density can also be measured in several ways. E.g. conventional densitometers or Mohr's dragonflies, or so-called beer scales using Archimedes' law or pycnometers, in which the weight of the fluid is determined at a constant and predetermined volume of the vessel. The density value is then calculated based on the known volume and measured weight.

A large number of viscometers are described in the patent literature, e.g. the rotary type in US 4,643,021. Also interesting are the solutions described in DE 19 840 868, where the measuring element is placed on a spring or EP 1 462 775, where the measurement is based on sensors or EP 1 674 865, where the measurement is based on a piezoelectric effect. EP 1 698 880 describes a device for measuring both viscosity and density, but using the resonant principle. U.S. Pat. No. 4,741,200, U.S. Pat. No. 4,905,499 and JP 3-123839 describe devices operating on the vibration principle, but in contrast to the solution according to the technical solution, they do not use levitation.

JP 59-221639 is closest to the solution according to the technical solution. It is a device for determining the viscosity of a liquid based on the vibrations of a ferromagnetic body located in the liquid. The body levitates between two electromagnets. The difference between the equipment according to the technical solution and JP 59

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221639 is that the device according to the technical solution uses only one electromagnet instead of the two used in JP 59-22 1639, the weight of the measuring element is used instead of the lower electromagnet. Furthermore, in JP 59-221639, the levitating element is vibrated by the fact that the electromagnets are supplied with an oscillating electric current. So this is a different principle. In JP 59-221639, the levitation element is immersed completely in the liquid under investigation, the beam of the light barrier illuminates it, so it can only be used for an optically transmissive liquid. The vessel must also be optically transparent, which in some cases can be a complication (aggressive liquids, high temperature melts). The device according to the technical solution has an element which is partially immersed and partially protrudes, the light barrier senses above the liquid. The device according to the technical solution can therefore also be used for opaque liquids and containers. In addition, the device according to the technical solution can also be used to measure the surface tension of a liquid and its density.

Furthermore, SU 1 762 187, which works on the levitation principle, is approaching the solution according to the technical solution, but there are several serious differences. The device according to SU 1 762 187 has position sensors located in the liquid. Equipment according to the technical solution above the liquid. Both solutions can have advantages and disadvantages. SU 1 762 187 does not state the principle on which position sensors work. However, if they were optical sensors, it would not be possible to use them for opaque liquids. Even in the case of a sensor principle other than optical, it would be very problematic to use for high temperature fluids (melts) or aggressive fluids. The solution according to the technical solution with a light barrier outside the liquid makes it possible to measure both opaque liquids and, with a suitable arrangement, also melts and aggressive liquids. The device according to SU 1 762 187 measures only the viscosity, while the device according to the technical solution is also able to measure surface tension and density. The device according to SU 1 762 187 causes the measuring element to oscillate by the electromagnet generating a magnetic field of opposite polarities. The principle of the device according to the technical solution is different, the electromagnet exerts a force only in one direction (upwards), the earth's gravity acts in the opposite direction and the element is oscillated not forcibly, but spontaneously oscillates when setting up a regulated system.

Overall, no device is known which uses the vibration-levitation principle and is able to measure both viscosity and density and surface tension.

The essence of the technical solution

Since the technical solution concerns one device (and thus one connection), which can measure the values of three different physical quantities only on the basis of switching to the given mode, the device and the method of measuring individual quantities for better comprehensibility will be described separately first for viscosity measurement, then for surface tension and finally density measurement.

The information below concerning the description of the viscosity measuring device also applies adequately to the determination of surface tension and density.

The essence of the technical solution is a device working on the principle of attenuation of vibrations of a body immersed in a liquid. This body (rod with a disc at the lower end, which can be immersed in liquids) is kept in space by electromagnetic levitation, resp. is in suspension. The electrical circuit enabling the levitation of the respective body is automatically interrupted at short intervals at certain times, thus causing the body to fall freely. By the subsequent start of the circuit, the body is pulled back again, the equilibrium is established and the whole system thus vibrates until the equilibrium is established. The equilibrium rate of a body is different in air from its equilibrium in liquids of different viscosities. Due to the different viscosities, the vibration attenuation is different. The registration of vibration dampings thus leads to the registration of the values of the intrinsic viscosities. The actual attenuation values are then visually displayed and stored in electronic form using special software, at the same time the temperature of the examined liquids and some parts of the device is registered. This data is also archived.

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The device consists of a photodiode, an electromagnet keeping the measuring body in suspension, an LED diode and a control circuit. It is either connected via a converter to the evaluation device or connected to a microcontroller, the connection further to the evaluation device being optional. The solenoid, photodiode and LED are unidirectionally connected to the control circuit, both diodes forming a light barrier. The control circuit controls the switching or expansion of the current by the electromagnet on the basis of the feedback from the light barrier, thus regulating the levitation of the measuring body. The control circuit therefore generates vibrations by switching off the current with the electromagnet for a few ms, amplifies and filters the signal from the light barrier for measurement by means of a computer.

The converter reads the signal from the light barrier (voltage on the photodiode). The amplitude of the signal oscillation, which is proportional to the amplitude of the mechanical oscillations, is evaluated. These are inversely proportional to the viscosity (the higher the viscosity, the smaller the oscillations).

The photodiode and LED according to this solution mean any suitable types, especially infrared.

The converter according to this solution means, for example, the USB6210 converter.

The evaluation device according to this solution means a computer, embedded microprocessor system, tablet, PDA, mobile phone, etc.

For proper operation, it is important that the levitating body is always in the same position (not rotating) under the electromagnet. Therefore, a special shape of the end of the electromagnet and the levitating body has been developed, when in principle a body of any shape capable of levitating in an electromagnetic field is usable, the "inverted armature" or "flat disk end" anchors appear to be the most advantageous.

This design has a number of advantages:

The device is very precise and sensitive and allows the registration of even very low viscosity values. This accuracy is achieved by almost zero friction of moving parts due to electromagnetic levitation. At the same time its small size and therefore easy mobility of the whole device. In contrast to the usually commercially manufactured viscometers operating on the principle of rotation and registration of the torsional force of the liquid acting on the rotating body of the device according to the technical solution, it is largely resistant to geometric irregularities of moving parts. Low production costs, compared to commercial models, production costs are lower by an order of magnitude. Possibility of easy and fast switching of the device between the modes of measuring the values of viscosity, density and surface tension of liquids.

When measuring the surface tension, the body is not fully immersed, but only wets the surface of the liquid. Due to the different values of surface tension, the liquid level is differently deformed. The registration of the deformation of the liquid level (ie the force required to tear the body from the liquid) thus leads to the registration of the values of the actual surface tension (the deformation of the liquid level is a function of the surface tension). The actual deformation values are then visually displayed and stored in electronic form using special software, at the same time the temperature of the examined liquids and some parts of the device is registered. This data is also archived.

When measuring density, neither vibration nor vibration measurement occurs, but the current flowing through the coil is registered. The measured current is a function of density, ie it is inversely proportional to density. The actual current values are then visually displayed and stored in electronic form using special software. At the same time, the temperature of the examined fluids and some parts of the device is registered. This data is also archived.

The device is not substantially limited by the type of fluid under the conditions of using a suitable construction material that comes into contact with the fluid so that it does not interact in aggressive environments. The advantage is the possibility of registering values even for liquids with very low viscosity, density or surface tension.

In order to verify the correct function and stability of the device, several liquids were measured. Typical outputs from these measurements are shown in the accompanying drawings.

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Clarification of drawings

The technical solution is explained in more detail with the help of drawings, in which:

Figure 1 is a front view of the shape of the electromagnet and the levitating body, Figure 2 is a side view of the shape of the electromagnet and the levitating body, Figure 3 is a plan view of the end of the electromagnet and the levitating body, Figure 4 is drawn overall diagram of the device, Figure 5 is a graph of a typical output signal for oscillations in air and glycerin when measuring viscosity, Figure 6 is a graph of the voltage at the barrier on the disconnection time of the circuit for different viscous liquids, Figure No. 7 is a graph of the calibration curve, ie the stress on the barrier as a function of viscosity, Figure 8 shows a graph of the stability test of the device for 25 hours, ie the dependence of the voltage on the barrier as a function of time, Figure 9 shows a graph The dependence of the excitation current on the coil on the temperature of the investigated liquid during the density measurement and in Figure No. 10 the most advantageous shapes of the levitating body are drawn.

Exemplary embodiments

Example 1- Apparatus for determining viscosity, density and surface tension values

The device 8 according to Fig. 4 consists of an IR photodiode 1, an electromagnet 3 under which the body 2 is suspended, an IR LED diode 4 and a control circuit 5. It is connected via a USB 6210 converter 6 to a PC 7. IR photodiode 1 and IR LED 4 they form a light barrier. The control circuit 5 controls the switching or expansion of the current by the electromagnet based on the feedback from the light barrier, thus regulating the levitation. Converter 6 senses the voltage on IR photodiode 1.

Example 2- Viscosity measurement

First, the electromagnetic levitation circuit turns on. The body 2 is then hung under the electromagnet 3. The glycerin container 9 is placed on an adjustable pad under the levitating body 2 and slowly raised so that the end of the body 2 is immersed in the glycerin. Then, the generation of vibrations in the control circuit 5 starts, and finally, the evaluation software starts. The amplitude of the signal oscillation, which is proportional to the amplitude of the mechanical oscillations, is evaluated. These are inversely proportional to the viscosity (the higher the viscosity, the smaller the oscillations).

Example 3 - Surface tension measurement

First, the electromagnetic levitation circuit turns on. Then the body 2 is hung under the electromagnet 3. The container 9 with the measured liquid is placed on an adjustable pad under the levitating body 2 and is slowly raised so that the body 2 is only wetted on the surface by the liquid. Then, the generation of vibrations in the control circuit 5 starts, and finally, the evaluation software starts. Deformations of the liquid level are evaluated. Deformation of the fluid level is a function of surface tension.

Example 4 - Density measurement

First, the electromagnetic levitation circuit turns on. Then the body 2 is hung under the electromagnet 3. The container 9 with the measured liquid is placed on an adjustable pad under the levitating body 2 and is slowly raised so that the end of the body 2 is immersed in the liquid. Then the software starts

-4GB 25212 The UI registers a current flowing through the coil. The current flowing is a function of density (the higher the current, the lower the density).

Industrial applicability

The equipment can be used in a wide range of materials research and development, as well as for testing existing products. The basic market segments include the chemical and pharmaceutical industries, the food industry, medicine, engineering, the glass and automotive industries, and more. The device can therefore be operated in laboratory conditions in primary research as well as in industrial applications to determine the properties of various types of oils, in the food industry, for example in the dairy industry, in medicine to measure blood viscosities in various diseases and in radiology in measuring properties contrast solutions and in general in fluid flow industries. It is also worth mentioning the automotive industry, where knowledge of these properties is important not only in terms of engine oils, but also brake fluids and the paint industry.

Claims (4)

PROTECTION REQUIREMENTS Levitation-vibration device for measuring viscosity, density and surface tension, characterized in that it consists of a photodiode (1), an electromagnet (3) holding the measuring body (2) in suspension, an LED diode (4) and a control circuit (5). ), where the photodiode (1), the electromagnet (3) and the LED (4) are unidirectionally connected to the control circuit (5), the photodiode (1) and the LED (4) forming a light barrier. The levitation-vibration device for measuring viscosity, density and surface tension according to claim 1, characterized in that it is further connected to the evaluation device (7) via a converter (6). Levitation-vibration device for measuring viscosity, density and surface tension according to claim 2, characterized in that the transducer (6) is replaced by a microcontroller. Levitation-vibration device for measuring viscosity, density and surface tension according to any one of the preceding claims, characterized in that the photodiode (1) and the LED (4) are infrared.