HU209352B - Measuring instrument - Google Patents

Abstract

Measuring tool for the measuring various characteristics of fluids containedin a tank of the type that consists of a pendulum (4); a propulsion means forcreating the vibration and maintaining the pendulum; a position measurementdesign, for example in the form of a drum; and a cable type element (2)connected to this position measurement device that is equipped on its freeend with a measuring entity (3) where conduits (12, 13) are provided on thependulum (4) for the cable type element (2), thereby characterized by thefact that the previously named fibre conduits (12) and (13) are placed atvarious distances with regard to the hinge point of the axle (14) of thependulum (4).<IMAGE>

Description

More particularly, the present invention relates to a measuring device for dynamically measuring the properties of liquids, such as the density and viscosity of a volume.

A measuring device according to the invention for measuring the level of liquids, for determining interfaces between layers of liquids of different densities, and for determining their levels, for measuring the density of liquids at different levels, taking into account one or more markings; measuring the viscosity of liquids at various levels; a device for measuring the levels of liquid tanks and fluid ducts and measuring differences in levels, which operates in response to markings and interfaces between fluid levels and / or layers of fluid of variable density.

The measuring device according to the invention is particularly suitable for conducting measurements in liquid tanks and fluid transport channels, particularly when there is a temporary or continuous risk of explosion due to the presence of dangerous gases or vapors on the liquid surface and when storing liquids or gases at higher or lower atmospheric pressure. .

For this purpose, the operation of the measuring device according to the invention is based on the principle of measuring the mechanical stress of vibrations or oscillations in a cable, wire or the like, known for carrying out the aforementioned and other measurements.

To accomplish this object, a measuring device is provided comprising a pendulum, a drive means for causing and maintaining the pendulum oscillation, preferably a position measuring device in the form of a drum and a wire connected to the position measuring device and a control and evaluation device. and guides arranged at least on the pendulum for sewing. It is an object of the invention that the guides arranged on the pendulum are spaced apart from the pendulum axis.

The measuring device according to the invention has the following advantageous effects:

- allows the measurement of the properties of liquids in the fluid reservoirs without affecting the ambient atmosphere and any electrical controls present;

- no electrical signals are applied to the liquid surface and / or pressurized areas in the hazardous area;

- can be installed and removed without creating any risk of escape of potentially dangerous substances in the tank;

- even when first installed, allows independent determination of the vertical dimensions of the liquid container in question and the measurement of the absolute level differences between the liquid or variable density fluid interfaces with the container, in which these differences are determined by one or more conventions; in units of measurement, such as mm or fractions of mm.

In a preferred embodiment of the measuring device according to the invention, additional fixed guides are provided for the wire under the pendulum, at a distance from the pendulum's axis of rotation, in the frame of the measuring device. Advantageously, the pendulum guides and the fixed guides are arranged such that the distance between the guide on the pendulum on one side of the wire and the guide on the pendulum is less than the distance between the guide on the pendulum and the guide on the other.

In another preferred embodiment, the distance between the guide member arranged on the pendulum and the guide member in the fixed position is equal on both sides of the wire.

The measuring device according to the invention may optionally be arranged so that the distance between the guides arranged on the pendulum is different from the distance between the guides in the fixed position.

Alternatively, the distance between the guides arranged on the pendulum is equal to the distance between the guides in the fixed position.

In the measuring device according to the invention, it is advantageous for the pendulum return torque to be equal on both sides of the pendulum at the same amplitude. Optionally, however, the pendulum return torque may be different on both sides of the pendulum at the same amplitude.

In the measuring device according to the invention, a pair of guides in fixed position is preferably arranged above the guides fixed on the pendulum.

The measuring device according to the invention will now be described in more detail with reference to the accompanying drawing, without limiting it thereto.

Figure 1 is a schematic diagram of a measuring device according to the invention; the

Fig. 2 is a side view of the above measuring device in arrow F2; the

Figure 3 is a front view of an exemplary pendulum; the

Figure 4 illustrates the configuration of a measuring device according to the invention.

As shown in Figures 1 and 2, the measuring device according to the invention comprises a position measuring device 1 in the form of a drum, a wire 2, a measuring body 4, a pendulum 4 and a mechanical filter 5 in the form of a rope, ribbon, cable or the like.

The wire 2 is guided between guides 6 and 7, 8 and 9 and optionally 10 and 11, fixed in the frame of the measuring device, and guides 12 and 13 arranged on the pendulum.

If the maximum amplitude of the pendulum 4 is small, so that the wire 2 is in constant contact with the fixed guiding member 7, the guiding member 6 is not required.

The dimensions of the aforementioned drum 1 are chosen so as to accommodate a wire 2 of sufficient length which is the total measuring length of the measuring body 2.

EN 209 352 required to move along the B-axis. The drum 1 may be provided with a helical groove in order to achieve greater accuracy in the measurement.

The guides 12-13 of the pendulum 4 according to the invention are arranged offset relative to one another, that is to say they are disposed at distances R2 and R1, respectively, relative to the pendulum axis 14 of the pendulum.

Similarly, the fixed guides 8 and 9 are arranged at distances A1 and A2 relative to the fixed guides 6 and 7, which are different. Preferably, the guides 12-13 arranged on the pendulum 4 and the guides 8-9 in the fixed position are arranged such that the distance between the guide 12 and the guide member 8 on one side of the wire is different from the distance between the guide member 13 and guide 9 side.

The distance between the guide elements 12 and 13 may be the same or different from the distance between the guide elements 8-9, depending on the particular measuring arrangement.

With the offset position of the guide members 12 and 13 disposed on the pendulum 4 and the offset position of the guide members 8 and 9 in the fixed position, the following advantages can be achieved, among other things, over a measuring device in which such wire guide members are arranged side by side:

1. Wire adhesive contamination means less problems, in other words, contamination of the wires guided by offset guides does not significantly or at all affect the wire 2 in the helical groove of the drum. In fact, dirt remaining on guides 12, 13 and guides 8, 9 will not be able to overcome the distance between guides 12,13 and guides 8,9;

2. Because guides 12-13 and guides 8-9 are offset relative to one another, the jamming of the wire 2 between guides 12-13 and guides 8-9, such as deformation, damage to the wire-shaped member 2, or the like for reasons, it is completely excluded;

3. Any capillary action between the wire-shaped member 2 and / or the guides 12-13 and / or the guides 8-9 is completely eliminated by pushing the guides 12-13 and / or guides 8-9 ;

4. A further advantage is that the position of the wire 2 in the pendulum 4 or in the measuring frame is not critical due to the offset arrangement of the wire guiding elements.

Although the aforementioned advantages have always been discussed with reference to the guides 12-13 and / or the guides 8-9, it will be appreciated that these advantages also apply to any guides 10 and 11.

Obviously, the relationship between the rotation of the drum 1 and the vertical movement of the measuring body 3 must be known accurately if the drum 1 is to be properly driven, for example by a stepper motor, a rotating magnet provided with an electromagnetic drive, or other suitable device.

The wire 2 must be sufficiently thin and flexible to remain taut even under the action of the smallest sensible force, such as when sensing the bottom of a liquid container. In addition, it must be strong enough to withstand the greatest force to be measured. The wire 2 must also be capable of being connected to the winding system without being distorted or broken.

The required measuring accuracy determines the elongation of the wire 2 under mechanical stress and its extension at ambient temperature.

The measuring body 3 is preferably cylindrical or spherical. The measuring body 3 consists of a material of suitable specific gravity, the weight of which is selected such that, after immersing the measuring body 3 in a liquid of maximum density, apply sufficient tension to the wire 2 to hold it tight.

The aforementioned measuring body 3 is designed in its final form to carry only a minimal amount of liquid when it is withdrawn from the liquid.

The pendulum 4, which enables the measured value of the voltage in the wire 2 to be converted into a measuring signal, is pulled back to its rest position by means of the wire 2 with a force the magnitude of which depends on the weight applied to the wire 2, namely weight.

The oscillatory movement of the pendulum 4 is created and maintained by a logic control unit which also serves to record and process the resonance signals emitted by the pendulum 4.

In a preferred embodiment of the measuring device according to the invention, the pendulum movement of the pendulum 4 is made by means of a permanent magnet (not shown in the accompanying drawing) attached to the oscillation axis 14 and by an electric magnet connected to the aforementioned logic control unit. guiding principle.

This logic control unit may consist of a microprocessor for controlling the position of the measuring body 3 and for controlling the oscillation of the pendulum 4, in addition to resonance generated by the latter. Such a control unit can make the measurement results accessible to those skilled in the art and allow the control signals and any parameter to be received.

The mechanical filter 5 serves to prevent the acceleration forces in the wire 2 from being generated by the oscillation of the pendulum 4 under the influence of the measuring body 3.

The combined resonance frequency of the probe 3, pendulum 4, mechanical filter 5 must be effectively damped to avoid influencing the operation of the pendulum 4.

This resonant frequency must be outside the frequency range of the axial vibrations generated by the pendulum 4 in the wire 2. The mechanical filter 5 may, for example, consist of a resilient material such as plastic or synthetic material, a spring or the like.

Before describing the operation of the measuring device according to the invention, let us first review the pendulum 4 of Figure 3

Figure 3 shows a pendulum 4 made of wire 2 on which a mass 15 is suspended. This mass of 15 swings around a fixed point of oscillation A. A fixed wire guide B is provided for the wire 2.

The self-oscillation period of this pendulum 4 is not symmetrical, so that the time it takes for the pendulum 4 to travel between points a-c-a is different from the time it takes to travel a-c-a.

These cycles are:

T _a , _b , _a = TG <I7j

^ Ta. _a = TGVL2 / g

Time required to travel a-b-a-c-a:

T = T a-b-a-c-a = T a-b-a + a-c-a

T = TG ^ l / g (VLT + <2)

In this formula, G is a constant of difficulty, while L1 and L2 are equivalent pendulum lengths.

Applying this relationship to the system shown in Figure 1 and to an embodiment in which the distance E between the fixed guides 6-7 and the pivot axis 14 is equal to zero, we obtain:

T = TG <j / S {V (A2-R2XA2xR2H (A (A1-R1) / A1xR1)}

In this case, the friction in the system is neglected and the notations are as follows:

S: voltage of the 2 wires,

J: mass moment of inertia about the oscillation axis 14.

As is known, the return torque of a pendulum depends on its amplitude. Since the construction according to the invention is asymmetric, the torque is different for a pendulum of the same amplitude.

However, if the torque of the pendulum is compensated by akaquk, then we must assume that:

A1-R1 is A2-R2

- = - = Constant

AlxR1 A2xR2 so that the torque of the pendulum is equal if its amplitude is equal.

It is clear from this comparison that the distance A1 may be different from the distance A2 if the distances R1 and R2 are the same for the same torque and the pendulum amplitude is the same. Indeed, if distance A1 were equal to distance A2 and R2, guides 12-13 and guides 8-9 would not have to be slid relative to one another.

In a particular embodiment of the measuring device according to the invention, the fixed guides 8 and 9, and the guides 10 and 11 can be omitted, thereby making the distances A1 and A2 theoretically infinitely large without taking away any of the advantages described above.

In this case, the return torque is different for the right and left amplitudes because the distance R1 is different from the distance R2.

Accordingly, the following relation applies:

T = K / VS where T is the oscillation time of the 4 pendulum,

K = structural constant

S is the voltage in the 2 wires.

Thus, if the voltage S changes, the oscillation time T of the pendulum 4 will also change, since the structural constant K will remain constant and friction will be neglected.

In the event that friction cannot be neglected, the oscillation time of the 4 pendulum will be as follows:

rp k 1 ^T ~ v ^ = f ² where in a wood system, or in other words, the degree of friction of the wire 2 and the pendulum 4 in the assembly.

In the measuring device according to the invention, the voltage S is equal to the apparent weight of the measuring body 3. In this case

- the weight of the 4 pendulum,

- the dead weight of the wire 2 is neglected.

The measuring device for measuring the various properties of the liquid materials of the present invention operates as follows.

The measurement of the fluid level is based on the fact that the frequency of the pendulum 4 is determined by the weight of the measuring body 3. Immersion of the measuring body in a liquid would reduce its apparent weight and thus reduce the frequency.

It is obvious that the immersion of the measuring body 3 in a liquid, for example at half height, coincides with its own frequency (fr), which was chosen as the reference frequency.

It follows that a liquid level measurement requires an adjustment system to change the position of the measuring body 3 until the amplitude frequency coincides with the reference frequency (fr). In this case, when the rotation of the drum 1 about the axis is controlled by a stepper motor, this means that the number of steps the motor takes in the same direction corresponds to the level difference of a reference level.

To measure the fluid level between the two layers of fluid, as in the previous case, it is sufficient to select a reference frequency (fr)

Transfer the reference frequency to the logic control unit and measure the level difference from the reference point.

The use of the measuring device according to the invention is illustrated in Figure 4.

The figure shows a container 16 provided with a measuring device according to the invention, which in this example is arranged at the top of a tube 17. This tube preferably extends into the container 16 and serves as a guide for the measuring body 3. The inner space of the tube 17 is permanently connected to the contents of the container, for example through a slit 18 which extends along the entire height of the container 16. The contents of the container 16 are comprised of two liquids 19 and 20 of varying density, the levels of which are located at heights X-X and Y-Y.

The aforementioned tube 17 is preferably provided with two stop members 21, 22 which are used as reference points. However, these stop elements 21, 22 are not necessary as the bottom container and the lower part of the measuring device can also be used as stop elements.

To determine the upper mark, it is sufficient to slide the measuring body 3 upwards until it touches the stop member 22. As a result, the voltage in the mechanical filter 5, preferably in the spring, increases and the weight of the measuring body 3 appears to increase, and consequently the resonance frequency also increases. The value of this frequency thus indicates the position of the measuring body 3 if it is sufficient to enter this value into a setting system such as a microprocessor. In this way, the level of the reference point coincides with a change in height equal to zero.

The highest marking point (stop member 22 or bottom 23) is determined in a similar manner, except that the impact of the body 3 against the body 22 or bottom 23 will reduce the apparent weight of the body 3 and consequently reduce the resonance frequency. This frequency, which is transferred to the adjustment system, is a criterion for maximum height difference.

Due to the fact that the apparent weight of a body immersed in a liquid depends on the density of that fluid, it is sufficient to place the measuring body 3 successively below the levels indicated by the YY and XX lines by resonance signals transmitted to the density system to determine.

Similarly, the viscosity of a liquid can be measured. It is obviously known that the friction of the liquid in question on the measuring body 3 during its constant speed movement is proportional to the viscosity of the liquid. This viscosity can be determined by the apparent increase or decrease in the weight of the body 3 and the change in frequency of the pendulum 4 associated therewith.

Due to the minimal amplitude of the pendulum 4 and the negligible friction in the fixed positions 6-9 and 12-13 of the wire 2, the latter can be gradually moved without disturbing the measurement.

It should also be noted that the control of the wire 2 is positive. This means that the movement of the wire 2 is effected such that it is a consequence of the movement of the pendulum 4 in a special plane. The consequence of this is that unwanted displacements of the wire 2 in other planes are excluded, which is of course very advantageous in terms of measuring accuracy of the measuring device in question.

Further, the additional guides 10 and / or 11 provide adequate attenuation of the unwanted amplitudes of the point 24.

It should be noted that the non-linearity of the pendulum 4 is processed by the measuring body 3 and the mechanical filter 5.

After all, any change in the height of the 24 points is proportional to the square of the amplitude angle of the pendulum 4, which results in a very strong acceleration of these 24 points. In order to avoid the effect of these accelerations on the measurement, the measuring body 3 is connected to the wire 2 by means of a mechanical filter or spring 5, thereby providing an effective damping of these accelerations.

The mechanical filter or spring 5 must be dimensioned so that the frequency of the measuring body 3 and the mechanical filter 5 is less than twice the minimum frequency of the pendulum 4.

So _

1/2 TG AIK / m <2xmin (1 / T) where: K = structural constant (spring constant) of the 5 mechanical filters, m = mass of the 3 measuring bodies,

T = the oscillation time of the 4 pendulums.

In any case, the frequency of the measuring body 3 and the mechanical filter 5 must be outside the frequency spectrum of the pendulum 4 in order to avoid the resonance of the measuring body 3 with the frequency or harmonics of the pendulum 4.

It is to be understood that the present invention is not limited to the embodiments described above, but may be embodied in all shapes and sizes.

Claims (9)

A measuring device for measuring the physical properties, in particular the quantity, density and viscosity of liquids in a container, comprising a pendulum, a drive means for causing and maintaining the pendulum oscillation, preferably a position measuring device in drum form and a wire connected to the position measuring device; a measuring body is attached to the free end of the wire, and guides are arranged at least on the pendulum, wherein the guides (12,13) arranged on the pendulum (4) are spaced apart from the pivot axis (14) of the pendulum (4). A measuring device according to claim 1, characterized by Further, for guiding the wire (2) under the pendulum (4), further fixed guides (8, 9) are arranged on the measuring device frame, at a distance (A1, A) from the pendulum axis (14) of the pendulum (4). THE 2). Measuring device according to claim 2, characterized in that the guides (12,13) arranged on the pendulum (4) and the guides (8,9) in the fixed position are arranged so that one side of the wire (2) is arranged on the pendulum (2). 4) the distance between the arranged guide member (12) and the fixed guide member (8) on the other side of the wire (2) is less than the distance between the guide member (13) arranged on the pendulum (4) and the fixed guide member (9). Measuring device according to claim 2, characterized in that the distance between the guide element (12, 13) arranged on the pendulum (4) and the fixed guide element (8, 9) is equal on both sides of the wire (2). Measuring device according to claims 3 and 4, characterized in that the distance between the guides (12, 13) arranged on the pendulum (4) is different from the distance between the guides (8,9) in the fixed position. Measuring device according to claim 3 or 4, characterized in that the distance between the guides (12,13) arranged on the pendulum (4) and the guides (8,9) in the fixed position are equal, 7. A measuring device according to any one of the preceding claims, characterized in that the return torque of the pendulum (4) is equal on both sides of the pendulum (4) at the same amplitude. 8. A measuring device according to any one of claims 1 to 3, characterized in that the pendulum return torque at the same amplitude is different on both sides of the pendulum (4). 9. A measuring device according to any one of the preceding claims, characterized in that a pair of fixed guides (6,7) is arranged above the guides (12,13) fixed on the pendulum (4).