CZ2013482A3 - Float-type flow meter with electric output - Google Patents

Abstract

A float flowmeter extending from at least one tube (3) in which a float (4) of electrically conductive material is disposed and a coil (1) is wound from the electrically nonconductive material outside the tube (3), the thread pitch changing from one the end of the coil (1) to the other end of the coil (1), the coil (1) being connected to the coil inductance measuring device (1).

Description

Technical field

The invention relates to a float flow meter consisting of at least one tube in which a float is placed.

BACKGROUND OF THE INVENTION

Float flowmeters work either on the principle of variable cross-section, ie with a guided float, or with rotation stabilization - rotameters, or with variable force with an inserted spring. As sensors without electrical output, they are cheap, reliable and rotameters are very accurate.

The basic problem is to convert the float position inside the flowing medium into an electrical signal.

The solutions used are discontinuous, in which the sensor detects the passage of the float through a specific position, either through an optical barrier or, for example, inductively by passing a coil that is wound at a particular sensor location or with mechanical transmission outside the tube. position, optically, camera.

Discontinuous solutions can be difficult to use for regulation - the replacement of continuous regulation by two or multi-position results in a large fluctuation of the controlled quantity with all especially economic consequences.

Exerting the float position outside the tube may result in measurement inaccuracies as friction increases, and the system is expensive and malfunctioning.

Optical camera imaging requires demanding evaluation - a relatively expensive embedded computer, space for camera installation, and is prone to soiling both the tube and the camera lens.

Image evaluation is software-intensive and, like any such solution, unreliable, such as the possibility of detecting a drop shadow or a flying fly instead of a float.

SUMMARY OF THE INVENTION

The above drawbacks are overcome by an electric output float flow meter consisting of at least one tube in which a float is positioned according to the present invention. It is based on the fact that the float is of electrically conductive material and a coil is wound outside the tube of electrically non-conductive material in which the thread pitch changes from one end of the coil to the other end of the coil, the coil being connected to the inductance measurement device. coils.

The tube may be cylindrical and the float is spring loaded, or conical and the float is in the shape of a rotating float. The tube is preferably transparent. The float need not be metallic if it has a different permeability than the flowing liquid.

One tube can be attached to another tube without a float.

A coil is wound outside the tube, the thread density, i.e. the pitch increases from one end of the coil to the other and the inserted float - metal or other conductive material, changes its coil inductance value according to its position, which can be easily evaluated.

The advantages of the proposed solution are especially that it is a very cheap solution, which is simple, so very reliable. The evaluation circuits for obtaining a continuous output are also cheap - inductance can be easily converted to frequency and digitized, the output can then be solved by a single-chip computer without the need for expensive A / D converters, stabilized voltages and the like. The flowmeter can measure a wide range of liquids regardless of conductivity and gases, and can also measure opaque liquids or gases.

The flowmeter has a long lifetime, especially with a rotating float solution, the only movable component is a wear-free float - less wear on abrasive fluids, less impact on electrical output than other types of flow meters. The solution is easy to maintain - float flow meters have less susceptibility to fouling than other flow meters with electrical signal output. No moving element in this solution

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The change in coil inductance for a given medium depends largely on the float position; slight variations in temperature or medium composition can be easily compensated for at the level of precision and cost we choose, with full compensation doubling the price of the meter. The reel can be designed in such a way that the float is still visible by the gap between the threads and orientation sighting is still possible - in many applications no additional display or second flowmeter will be required at the measurement site, as is the case with other solutions.

The device retains the possibility of creating a float flow meter even for very small flow rates that are otherwise difficult to measure if electrical output is desired.

Electrical sensing makes it possible to use very low power circuits because only passively position measurement and no additional signals are generated, as is the case with ultrasonic flowmeters, but especially for induction and thermal flowmeters. This makes it possible to carry out the entire electrical position sensing with battery supply or accumulators.

The battery-powered option facilitates use in explosive environments as well as in health care, as there is no risk of electric shock in the event of equipment failure, for easier certification.

Compared to thermal flowmeters, another advantage is that the flowing fluid is not thermally influenced - in some cases heating of the fluid may be undesirable and also unnecessarily increases the power consumption.

Clarification of the figures in the drawings

The float flowmeter of the present invention will be described in more detail with reference to the accompanying drawings, in which: Figure 1 shows a cross-sectional flowmeter with a cylindrical tube. In FIG. 2 is a cross-sectional view of the flow meter with a conical tube. FIG. 3 is a cross-sectional view of a two tube flow meter; and FIG. 4 is an exemplary wiring diagram.

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DETAILED DESCRIPTION OF THE INVENTION

Example 1

Giant. 1 describes an embodiment based on a flowmeter with an inserted spring 2. The fluid flow 7 acts against the float 4, the force is balanced by the spring 2. When measuring the flow with variable force, the tube 3 is generally cylindrical. The tube 3 is made of a non-conductive material. The flow meter is terminated by flanges 5 and 6, which can be suitably adapted to the pipe connection requirement. The position of the float 4 results in a change in the inductance of the coil 1, which is evaluated. The thread density of the coil 1 varies from low in the lower part to large in the upper part, but it can also be the opposite. The float 4 must be of a conductive material, typically metallic, but need not be metallic if it has a different permeability than the flowing fluid 7. Changing the dimensions of the spring 2 when compressed can affect the resulting inductance, which can be compensated by calibration. The advantage of this arrangement is that it is possible to use any plastic for the tube 3 and the flanges 5 and 6, or even to produce it as a single piece, which significantly reduces the cost of the flow meter. Another advantage is the possibility of mounting in any position. Both are a feature of the known float flowmeter solution, which is supplemented by an electrical evaluation of the float position 4.

Example 2

Giant. 2 depicts an embodiment based on a rotating float flow meter. The flow of the fluid 7 acts against the float 4, the force is balanced by the weight of the float 4. The pressure drop is given by the weight of the float 4 and is constant, the tube 3 is conical - the cross-section widens upwards. The tube 3 is made of a non-conductive material. The flow meter is terminated by flanges 5 and 6, which can be suitably adapted to the pipe connection requirement. The position of the float 4 results in a change in the inductance of the coil 1, which is evaluated. The thread density of the coil 1 varies from low in the lower part to large in the upper part, but it can also be the opposite. The float 4 must be of a conductive material, typically metallic, but need not be metallic if it has a different permeability than the flowing fluid 7. In this arrangement, the tube 3 is typically glass, which can be manufactured with sufficient accuracy and shape stability including temperature and resistance against aggressiveness of the measured fluid and environment. There is no friction, so high measurement accuracy is achieved. Said advantages are the characteristics of the known solution of the rotameter, which has been supplemented with an electrical evaluation of the position of the float 4.

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Example 3

Giant. 3 illustrates a full compensation flow meter assembly. Coil inductance change 1 value Lj _; from the influences other than the position of the float 4 - the temperature of the fluid 7, the ambient temperature, the change in the permeability and the permittivity of the fluid 7 is compensated by the change in the inductance of the coil 1a by the Li value. The compensation is performed by the wiring shown in FIG. 4 - coils 1 are connected in a classical source of rectangular oscillations, where they replace the resistance of one of the RC cells, which determine the frequency of the illustrated multivibrator. The diodes used protect the inputs of the integrated circuit from destruction by possible flickering or static electricity. All six gates are part of a single integrated circuit, so the temperature change compensation is complete here. The use of two circuits allows to compensate the dependence of resistors and capacitances on temperature as well as the dependence of the connection on the supply voltage - to the extent of the permissible power supply of the integrated circuit. Both multivibrators must be enclosed in a common plastic box in order to have the same external effects. Compensation is done by measuring both frequencies with a single-chip microcomputer that can be connected to a serial output, for example to a computer, or to control a connected LCD display with a serial input. The advantage of this solution is the extremely low price.

Industrial applicability

The electric output float flow meter according to the present invention finds application as cheap and, in case of circuitry with error compensation circuits, accurate flow measurement not only in laboratories, for example for cooling water flow, but also for aggressive and / or opaque liquids or gases. The meter used must be calibrated for the medium to be measured.

Claims (5)

PATENT CLAIMS A float flow meter with an electrical outlet comprising at least one tube (3) in which a float (4) is located, characterized in that the float (4) is of an electrically conductive material and outside the tube (3) of an electrically non-conductive material A coil (1) is wound in which the pitch of the turns varies from one end of the coil (1) to the other end of the coil (1), the coil (1) being connected to the coil inductance measuring device (1). Float flow meter according to claim 1, characterized in that the tube (3) is cylindrical and the float (4) is provided with a spring (2). Float flow meter according to claim 1, characterized in that the tube (3) is conical and the float (4) is in the form of a rotating float (4). Float flow meter according to any one of the preceding claims, characterized in that the tube (3) is transparent. Float flowmeter according to any one of the preceding claims, characterized in that another tube (3) without a float is connected to one tube (3) with the float (4).