DK169574B1 - System for determining the vertical distribution of at least one medium - Google Patents

Description

in DK 169574 B1

The present invention relates to a system for determining the vertical distribution of at least one medium surrounding a measuring device and for determining a location for at least one boundary zone position thereof based on differences in thermal states and properties of this position, such as

specified in the preamble to claims 1 and 3. I

In the invention, vertical distribution of one or more media surrounding the measuring device can be determined, with which the positions of adjacent layers can be determined on the basis of the difference in the arrangement of one or more thermal sensor elements or temperature sensors having a thermal coupling to it. medium to be measured, applying heat energy to the medium adjacent to the respective element or sensor, and wherein said position or positions are recorded as a function of the amount of energy absorbed by the medium being absorbed. must be measured, at the measuring point, ie. the thermal conductivity of the medium.

In connection with continuous monitoring of tanks or storage rooms, constant monitoring of the position and extent of boundary layers as well as any formation of sludge zones is necessary. A sludge zone is defined as a mixing zone of substantially adjacent substances, but certain precipitating products may also be admixed, such as wax and other contaminants having a density which lies between the density of both of the principal media, such as crude oil and water in the present case. The boundary layers may consist of different forms of liquid, granules, gases and a combination of these. A particular object is to provide, in connection with production or storage at sea or in connection with large storage spaces in rocks, a measuring device for determining the positions of the boundary layers in crude oil storage tanks.

In the said storage systems, the boundary layers in the main case 35 consist of oil / water, but transition layers of liquid / gaseous and liquid / - precipitates or other forms of precipitation products are not uncommon- In addition, transition zones are often formed, especially at the boundary layer positions, as in the main thing consists of a composition of two or more of the components to be stored. They form so-called sludge zones with precipitates formed as a result, which can adversely affect measuring devices or the like.

In addition, the installations in the above situations cause great access difficulties and high costs in connection with maintenance, replacement, cleaning or other service.

There are various sensor systems based on thermal effects.

Published European Patent Application No. 0052215, 15 filed by the German VDO in 1981 discloses a principle according to which a pattern of resistance elements is etched from a substrate provided with a constant current. The voltage drop across the resistance elements will be higher or lower depending on whether the element is immersed in a liquid or not. Signal processing electronics subsequently connect the elements, voltage is recorded and the voltage level determines whether the element is completely or partially immersed in liquid. If an element is partially submerged, the extra level is achieved by interpolation between the 25 portion of the voltage drop that is in air and the percentage of the voltage drop that results from the portion of the element that is submerged in liquid.

A number of similar level measurement systems have been provided, especially in connection with fuel tanks on ships, in which resistance elements in the form of metal wires or various types of thin film technique are in direct contact with the medium to be measured, as also disclosed in French patent no. .

2533 311 in the name of Pras Jean Claude. A detailed description is also given in VDI-Berichte No. 509, 1984, pages 235-242.

DK 169574 Pg 3

It is common for the above measurement principles that they are mainly used for level measurement in fuel tanks containing clean products and that the measurement is made to determine the air-liquid interface. In addition, according to the prior art, the self-regulating elements must be in direct contact with the medium to be measured and long connecting lines to individual measuring elements should be avoided, as such lines easily contribute to errors. This means that signal processing should take place in the immediate vicinity of the self-regulating element.

Among other known level measurement systems that use thermal effects to detect level and boundary layer, mention should be made of different level measuring means measuring at separate points, in which the heat transport from a heating element to a medium to be measured is measured by means of a difference recording temperature measuring system. which is mainly based on a thermocouple comprising a large number of thermocouples which are serially connected.

Since the individual measurement points are connected consecutively to a suitable signal processing unit, the thermal transport at each measurement point will be an expression of the nature of the surrounding medium. From the relevant patent literature reference is made to NO-PS 133 517, GB-A 2 134 260, US-PS 2 702 476, US-PS 3 280 627 and DE-OS 19 59 041.

25 With respect to other prior art which is relevant for a closer understanding of the concept of elements made of electrically conductive composite material, reference is made to DE-C2 26 34 931.

It is common for measuring devices of the above type that 30 each measurement point is relatively expensive and complicated, especially if a useful contrast is to be obtained between signals from different measured media. Comprehensive and costly signal conditions will be required, especially when low signal levels are to be transmitted via long cables. In addition, good thermal control of the heat source and thermal masses incorporated in the system is required, as well as a stabilization of the temperature of the medium to be measured.

The measurement systems initially mentioned are characterized according to the invention by the features shown in the characterizing part of claims 1 and 3 respectively.

According to the invention, great flexibility is achieved in terms of resolution and signal power, as well as significant cost savings, both in terms of manufacture and installation. Thermal power applied to the measurement points depends on the thermal power delivered, which in turn depends on the thermal state and property of the surrounding medium. A major advantage is that the sensor element signal in the form of supplied electrical power and the necessary supply current for heating the element can be carried over the same connection lines.

The invention is based on thermal principles in that heat is transported to the medium to be measured from a self-regulating heating element, ie. applied power is a function 20 of the power absorbed by the medium to be measured.

In this way, a heat source and a sensor can be combined in one and the same unit. The self-regulating element regulates the applied electrical power as a function of the temperature of the element, where the temperature depends on the heat output to the surrounding medium. By constantly recording the applied power, a signal effect is obtained which is an expression of the composition of the surrounding medium based on thermal properties.

The sensor power is obtained by the fact that the active element in the sensor is made of a polymer mixed with a conductive carbon material which forms a large number of parallel electrical connections between substantially parallel connectors which are integrated into the element and form a connection. B1 5 points for the connection lines between separate sensor points and the signal processing unit.

Due to the fact that power is applied to the connecting lines, the intermediate semiconducting core material is heated and a microscopic expansion occurs, with a subsequent increase in resistance, which will then result in a reduction in power supply.

Conversely, a reduction in temperature will cause contraction of the material and thus a reduction of resistance, resulting in an increase in applied power. In this way, the self-regulating effect is obtained, which shapes the sensor signal appropriately.

There are various manufacturers of heating elements based on plastic materials which exhibit the above effect due to the incorporation of conductive materials, coal, metal particles or the like and which can be adapted to a sensor element in terms of shape and size. Completing the connection lines to individual sensor elements, both mechanical and electrical, is of great importance to achieve a stable element. In the embodiment of a sensor system shown here, the material of a heating cable having the above-mentioned regulating properties is used for practical reasons, and the termination between this material and the connection lines shows a suitable embodiment.

The above-mentioned example of the use of the material in the self-regulating element is given only to show a practical embodiment, without this being construed as a restriction on other materials having the same properties, but with a different embodiment, finishing etc. Among known product names 30, Raychem has a comprehensive range of heating cable products adapted to various objects in terms of working voltage, temperature range, power per unit length with different types of mechanical, electrical and chemical protection.

In a first embodiment, in a basic embodiment, the sensor system will comprise a series of separate self-regulating elements with a suitable vertical distribution. The connection lines connect each individual self-regulating element to a connector which allows each individual element to be connected to a circuit in which the applied power is measured in terms of the size and time of each element.

In larger sensor systems comprising a large number of measurement points, it may be advantageous to distribute connectors belonging to separate measurement points in suitable groups, arrays, or other known embodiments to address certain elements or groups over a minimum of connecting lines.

The simplest embodiment would be a larger or smaller group of self-regulating elements with a common connection, while the others are separately advanced to the connecting means. In some cases, it may be convenient to integrate connecting means with or near the self-regulating elements so that the separate elements can be connected to the common power supply controlled via signal lines, thereby reducing the line of connection for the sensor-connector module connection.

Determination of boundary layers occurs by sensing elements connected successively to a power source in an appropriate sequence. The applied power is recorded and the thermal properties and thus the position of the surrounding medium are determined on the basis of knowledge of the effect characteristic of the sensor element as a function of temperature.

In another embodiment, the self-regulating element 30 consists of a vertical distribution of the active sensor material with a cable-like configuration and of two connection lines for connecting a power source. The applied power will normally adjust to the average resistance value for the whole element's extent. The sensor may thus consist of one or more self-regulating elements.

In a third embodiment of the invention, the sensors are not formed by self-regulating elements, but are formed by temperature sensors of short, dot-shaped nature. However, a self-regulating element is used as a temperature reference and heat power supply source, thus providing the temperature sensors a signal that is a function of heat power absorbed by a medium adjacent to such a temperature sensor. Thus, by using temperature sensors which are suitably vertically distributed and having good thermal connection closest to the medium to be measured, one or more transition zones or a passage therethrough can be recorded using a single self-regulating element as a temperature reference, heat source .

In addition, within the scope of the invention, a combination of short dot-shaped sensors as well as elongated elements can be envisaged to meet specific requirements for a tank measurement system.

Due to some thermal transition resistance between the element and the medium, a temperature difference between element 20 and medium will occur. This temperature difference will vary vertically in the case where the self-regulating element is in a transition zone between two or more media to be measured and having different thermal properties.

A microprocessor controls signal processing and, on the basis of measurement data, can provide clear information about the measured medium surrounding the sensor with respect to the thermal properties of the medium which determine the power emitted by the self-regulating element.

The invention will now be explained in more detail 30 with reference to the accompanying drawing which represents a non-limiting embodiment of the invention.

FIG. 1 shows an active self-regulating element for use in the system according to the invention.

DK 169574 B1 8

FIG. 2 shows an example of the relationship between power and temperature.

FIG. 3 shows the active self-regulating element disposed within a protective tube.

FIG. 4 shows an elongated self-regulating element which cooperates with temperature sensors.

FIG. 5-8 show several examples of placement of one or more active self-regulating elements.

FIG. 9 is a cross section along section IX-IX of FIG. 8th

FIG. 10 shows an example of grouping connection lines for separate self-regulating elements.

FIG. Figure 11 shows an example of a complete sensor installed in an oil or water storage tank.

FIG. 12 shows a block diagram of connections between sensors, signal processing and display.

In FIG. 1, an active self-regulating element 1 with active material 4 is shown, which forms a large number of parallel flow paths between connecting lines 2 and 3. The material has an enclosing sheath 4 'of an electrically insulating material. 20 Power output per unit length is a function of the composition and temperature of the material.

FIG. 2 illustrates an example of a typical characteristic showing the ratio of applied power (W / ft) to temperature (degrees F) for various mixtures of the active material, labeled a, b, c and d.

FIG. 3 shows an example of how a self-regulating thermal sensor element 1 is thermally connected to the interior of a pipe wall 5 by means of a material 6 with good thermal conductivity to optimize the thermal contact 30 between the self-regulating element and the pipe wall. The junction material 6 may be of metal or a similar conductive material or, if desired, an adhesive or paste having good thermal conductivity. The self-regulating element may have some vertical extent which may constitute an independent system.

If desired, it may form a measuring point with some vertical extent, but will be considered a measuring point in a larger system, for example with more than 100 meters.

In FIG. 4 shows an example of how a plurality of measurement points can be established along the vertical extent of 5 a self-regulating element within a barrier 10. The element 1a will maintain a constant temperature within its control range due to its self-regulating function. The element la thus serves as a common heat power source for the measurement points. In FIG. 4, three separate thermal coupling means 11, 12, 13 are shown, each forming a separate thermal coupling with media 14, 15 to be measured. The latter have different thermal properties. For example, Medium 15, which may be water, may exhibit a higher heat absorption effect than Medium 14, which may be, for example, oil. Therefore, the temperature difference of 15 over the respective coupling means 11, 13, which is detected by means of temperature sensors 7, 9, will be different. The difference will be proportional to the difference in thermal conductivity and capacity of the media being measured. The thermal coupling means 12 will transfer thermal energy from source 1 20 to both media 14 and 15. This means that the temperature difference measured by temperature sensor 8 is higher than the temperature difference measured by temperature sensor 9 for water at 15, and lower than the temperature difference measured by oil temperature sensor 7 at 14. Temperature measurements provided by temperature sensors 7, 8 and 9 are transmitted via respective signal lines 7 ', 8' and 9 'to a signal processing unit 40 and are seen to have different temperature gradients of the display 41 in the form of diagrams 43.

FIG. 5 shows an embodiment in which the self-regulating element 1 30 is placed in good thermal contact with a connecting material 16 on the inside of a tubular barrier 10. In this way a radial thermal contact with the medium to be measured is obtained simultaneously. with the vertical extent of the measuring point being limited. The central portion 35 18 of coupling material 16 is open to allow space for connecting lines from self-regulating elements which are located further down (not shown in Fig. 5). FIG. 5 thus constitutes a variant of that shown in FIG. 4 and in the following FIGS. 8-11.

In FIG. 6, there is shown a flat embodiment in which the self-regulating element 1 'is in thermal contact with two of the lateral faces 19', 19 7 7 of the barrier 19. In this way, the thermal contact between sensor element 1 and the surrounding medium to be measured is enhanced via thermal coupling elements 20, 207 and the barrier surfaces 19 ', 19' '. The coupling elements 20, 207 may be of good thermal conductivity material. Cavity 21 provides space for electrical connections 22 to the self-regulating elements within the barrier.

FIG. 7 is substantially similar to the embodiment shown in FIG. 6, except that each thermal sensor element 1, 17, 177 extends horizontally relative to the vertical barrier 19. The sensor element has an elongated shape and a limited vertical extent at the measurement point; in order to increase the vertical resolution of level indication while maintaining the heat sensitivity of the element 20.

FIG. Figures 8 and 9 show a flexible solution of a device in which self-regulating thermal sensor elements 1, 177, 177,1'777 are arranged on a flexible tube-like core 23, which also forms a channel for feeding live conductors 2, 3 A protective barrier 24 consists of a flexible material, e.g., polyethylene or the like. For larger lengths, it may be appropriate to integrate a flexible member 25, e.g., steel, Kevlar® or other tensile strength material, to absorb tensile forces and make the length of the device stable to achieve vertical measurement accuracy.

In an integrated embodiment, in which the thermal sensor elements and supply lines, in principle, form a cable-like design, a uniform sensor system without DK 169574 B1 11 achieves any risk of fluid penetration, whereby the design is particularly suitable for underwater storage systems where an inaccessible end point between sensor elements and cable is placed in water at a fairly high pressure.

5 As can be seen from FIG. 8 and 9, the barrier 24 is elongated and tubular. Each of the sensor elements extends along a longitudinal portion of the barrier, each of the elements having a greater length than width.

In FIG. Figure 10 shows an example of how various self-10 regulating sensor elements ln, n = 1, 2, 3 ... 6 can be terminated in groups 26, among other things, to distribute the applied power appropriately. The connections 2 and 3 to the separate sensor elements are quite dependent on the addressing method used. In the embodiment shown, the sensor elements are provided with direct current and to avoid unwanted parallel connections, a blocking diode 27 is provided in the connection line 2 for each element.

FIG. 11 shows an example of a sensor installation in a storage tank 28 for oil 29 and water 30 respectively with an oil / -20 water transition zone 31. Self-regulating thermal sensor elements lx .... 16 may have a suitable vertical distribution, for example in the form of different mutual distance as shown, and they are surrounded by a steel pipe 32 which oil and water cannot penetrate. The device has a sensor head 33 with end 34 25 of the electrical connections to the sensor elements.

In FIG. 12 a simple block diagram of connections between the sensor element device and associated devices is shown. Separate sensor units 35, 35 ', 35' 'are connected, via multi-conductor cables 36, to a connector module 37 which connects the individual 30 self-regulating elements 1 of the sensor units 35, 35', 35 "in succession or in groups to a power supply 38.

Power applied to the individual self-regulating thermal sensor elements is measured and converted into an analog to digital converter 39. The signals are processed in a signal processor unit 12 and compared with measured values in a calibration table. Control of the connector module 37 is achieved by the signal processor unit 40 which, on the basis of the measurement results, can influence the connection of separate self-regulating 5 thermal sensor elements in a suitable manner, for example in groups as a function of level position and direction and power applied. A display 41 is an example of an opportunity to present an overview of the positions 42 of the respective transition zones. Temperature gradients 43 may be an integral part of the display 41.

The self-regulating thermal sensor element or elements may act like temperature resistors to measure the vertical distribution of the temperature of the surrounding medium to be measured. This is an important feature, since the temperatures of the fluids may initially be different, which will greatly increase the measurement effect. This is especially the case in the main application of the present system, for example storage tanks on a production platform, in which the differences in temperature between oil and water can reach 30 degrees or 20 more. By means of the signal processor unit 40, this information is extracted and can be displayed on the display 41 in the form of temperature gradient curves 43. This is not to be confused with fig. 4, where the temperature is obtained by special temperature sensors which only react to temperature, the temperature sensors being unable to provide heat to be absorbed by a medium located at such a temperature sensor.

An example of an application of said system is a production platform where crude oil is temporarily stored in large 30 storage cells containing oil and water with a vertical distribution.

The extent of the sensor unit comprises the total measurement area for the respective transition zones. The vertical distribution of measurement points can be adjusted to the resolution requirement. The separate 35 self-regulating thermal sensor elements are connected to power supply 38, individually or in groups, and power supplied to each element is measured and converted in analog to digital converter 39 into digital form for further signal processing in signal processor 40. The magnitude of power supplied is a function of the temperature of the element which is influenced by the thermal properties of the surrounding medium.

Since there is less heat loss from sensor unit to oil than from sensor unit to water, more electrical power will be deposited with respect to water than from oil. The relative difference between 10 measurement points for oil and water, respectively, is essentially given by the temperature gradient of the respective media to be measured, and to some extent by production tolerances for the self-regulating thermal sensor elements used.

The sensitivity characteristics of the individual self-regulating thermal sensor elements as a function of temperature in a known medium to be measured, e.g., water, can be incorporated as a calibration value for the complete sensor unit to form a reference table.

With said reference table included in the signal processing, it is possible to distinguish between different media and the vertical temperature gradients along the surface of the sensor unit. By means of a slightly more sophisticated signal processing, movements of different transition zones in the storage cells can be monitored so that only up-close self-regulating thermal sensor elements are activated at any given time, while the size and character of signal levels relative to reference values. and the position of the boundary layer will reflect the state of the measurement point with respect to coating formation, e.g., formation of 30 waxes. It will also be possible to distinguish between upper and lower boundary of a boundary layer zone, especially when passing several measurement points, for example when filling or emptying the tank.

In the case where a coating, such as a wax formation, is recorded around the sensor point, more power is applied in a period of time and / or in size, which will cause a higher surface temperature and prevent the formation of wax.

This can be controlled manually or form part of the signal processing routine. Especially in connection with storage cells 5, the sensor units will be exposed to wax precipitation. Therefore, it will be necessary to be able to control the applied power by means of the sensor elements to prevent such precipitation. Therefore, the self-regulating element has three functions: 1) to detect transition zones based on the thermal properties of the media, 2) to detect the temperature (gradients) of the media, and 3) to prevent and / or remove wax deposits.

The composition, consistency and temperature of the medium to be measured essentially determines the magnitude and duration of applied power. In addition, there is the requirement for response time.

There are two alternative ways of controlling the sensor units: a. Using the dynamic and static portion of the applied power characteristic, respectively, where the dynamic portion represents the decreasing drop characteristic as a function of time after the sensor element is connected, while the static portion is represented by the stable power level selected by the sensor element after a certain amount of time. In this case, the sensors or groups of these will be constantly activated (heated), while simultaneously applying power to individual elements. This method provides the fastest update time (response time) and the highest sensitivity to changes in the thermal properties of the medium. However, the correspondingly high amounts of energy will be required due to the large number of sensor elements connected at the same time.

b. Alternatively, the self-regulating sensor elements are connected separately and the dynamic behavior of each element from the moment of connection to a given time

Claims (21)

A system for determining the vertical distribution of at least one medium (14; 15; 29; 30) surrounding a measuring device and for determining a location for at least one boundary zone position (31) thereof based on differences in thermal conditions DK And properties of this position, comprising at least one thermal sensor element (1; 1,1 ', ln, l "', 12,13,14,15,16) / having means (6/16/20 , 20 ') for thermal coupling to a respective medium to be measured, and having a positive temperature coefficient with respect to electrical resistance, means (2.3 / 36, 37.39) for electrically coupling the sensor element to an input terminal on a signal processor unit (40), wherein the sensor element provides a signal to the signal processor unit related to heat power absorbed by the respective medium, characterized by means (37, 38) coupled to the signal processor unit (40) for supplying electrical power to the the element, the sensor element being self-regulating, is made of a 15 electricity an electrically conductive composite material consisting of a plastic material mixed with an electrically conductive material, having an electrically insulating sheath (4 ') and electrically insulated from and located within a common barrier (5/19/24/32) forming a physically protecting the element against 20 direct contact with each of the respective media, the barrier being surrounded by each medium, and means (37,39,41) coupled to the signal processor unit (40) for detecting boundary zone position as a function of heat power absorbed by each respective medium at the measuring point of a respective element due to thermal conductivity of the medium, for heat power caused by electrical power supplied to the element from the delivery means, the signal processor unit (40) being able to process a signal supplied from a sensor element (1 / 1.17.1 ", 1" / lx, 12.13.14.15, lg) as one of the following signals: - dynamic part of a heat effect absorption related signal delivered and - dynamic portion and static portion of the heat power absorption related signal provided by the sensor element. DK 169574 B1 17 System according to claim 1, characterized in that two or more thermal sensor elements (1; 1,1 ', 1 ", 1"'; 1-l, 12,13,14,15, lg) are arranged vertically above each other and that the electrical coupling means 5 (37, 39) individually and selectively couple each of the elements to the signal processor unit (40). A system for determining the vertical distribution of at least one medium (14; 15) surrounding a measuring device and for determining a location for at least one boundary zone position 10 thereof based on differences in thermal conditions and properties of this position, comprising a setting up two or more temperature sensors (7,8,9) arranged vertically above each other and having means (11,12,13) for thermal coupling to a respective medium to be measured, a signal processor unit ( 4) having a respective input terminal for each sensor (7,8,9) and means (37,39) for electrically coupling each of the temperature sensors to the respective input terminals of the signal processor unit, and wherein the temperature sensors each give a signal to the signal processor unit (40) related to heat power absorbed by the respective medium at a respective temperature sensor, characterized by means (1a) for supplying heat power to each of the sensors, the delivery means being electrically regulating, having a positive temperature coefficient with respect to electrical resistance, is made of an electrically conductive composite material consisting of a plastic material mixed with an electrically conductive material, having an electrically insulating jacket (4) and together with the sensors electrically insulated from and being within a common barrier (10) which provides a physical protection for the delivery means (1a) and the sensors (7,8,9) against direct contact with each of the respective media, the barrier (10) being surrounded by each medium (14,15) and 35 means (37,39,41) coupled to the signal processor heat (40) for detecting boundary zone position as a function of heat power supplied to each of the thermal switching means 16 (7,8,9) from the delivery means (1a) and which are absorbed by each respective medium (14, 15) at a respective sensor's measuring point (7,8,9) due to the thermal conductivity of the medium, the electrical coupling means (7 ', 8', 9 37,39) individually and selectively connect each of the temperature sensors (7,8,9) to the signal processor unit (40), and the signal processor unit (40) being able to process a signal supplied from a temperature sensor as one of the following signals. : - dynamic part of a heat power absorption related signal provided by the respective temperature sensor, and - dynamic part and static part of the heat power absorption related signal provided by the respective temperature sensor. System according to claim 1, 2 or 3, characterized in that the barrier (5; 10; 19; 24; 32) is made of at least one material selected from the group consisting of acid-resistant steel, polytetrafluoroethylene, nylon and polyethylene. System according to claim 1 or 2, characterized in that the sensor element (1) or elements (1; 1,1 ', 1 ", 1"', -1- 12,13,14,15,16), consists of a respective discrete length of self-regulating heating cable, which can be connected (2,3) to an electric power source (38) by means of the electrical power supply means (37,38). System according to claim 3, characterized in that the means (1a) for supplying electrical power consist of a respective discrete length of 30 self-regulating heating cables which can be connected to an electric power source (38). System according to claim 1 or 2, characterized in that the sensor element receives electric power and thereby provides heat power. DK 169574 B1 19 prevents the formation of a wax coating from a respective medium on the barrier adjacent to the element by detecting the thermal conditions and properties of the medium. System according to claims 3, 5, characterized in that the thermal coupling means (11,12,13) upon receiving heat effect prevent formation of a wax coating from a respective medium on the barrier adjacent to the respective temperature sensor by detecting the thermal conditions of the medium and properties. System according to claim 3, characterized in that the barrier (10) has an inner wall and a plurality of the temperature sensors (7,8,9) are arranged on this inner wall, the temperature sensors being used for measuring and recording a relative distribution gradient of 15 thermal transport along the barrier. System according to claim 3, characterized in that the means (1a) for supplying heat power are related to at least three of the temperature sensors (7,8,9) via the respective thermal coupling means 20 (11,12,13) which form respectively thermal connections to the inner wall of the barrier. System according to claim 1 or 3, characterized in that the means (37,39) for registering position for border or transition zone between two media comprise means for interpolating between vertically graduated media during registration at each of a plurality of vertically distributed measuring points when a medium is filled in or emptied from a storage container. System according to claim 2, 30, characterized in that the means (37,39,41) for recording the position of border or transition zone between two media record when a medium is filled into or emptied from a storage container. DK 169574 B1 20 System according to claim 1, 2 or 3, characterized in that the barrier (5; 10; 19; 24; 32) is elongated and tubular, that fasteners are provided for securing the sensor element or temperature sensor and associated thermal coupling means. (6; 11,12,13; 20,20 ') to the barrier, and the barrier further encloses the electrical connecting means (2,3 / 2', 3 ', 7', 8 ', 9'). System according to claim 13, 10, characterized in that the sensor element is physically contacted by the fastening means with the two opposite planar faces (19 ', 19 ") of the barrier. System according to claim 13, characterized in that the sensor element extends 15 along a longitudinal part of the barrier, the element having a greater length than width. System according to claim 13, characterized in that at least two sensor elements (1 / 1,1 ', 1 ", 1"'; 11,12,13,14,15,16) are arranged in an arrangement where the extending consecutively in the longitudinal direction of the barrier, each element calculated in the longitudinal direction of the barrier having less length than width. System according to claim 1 or 2, characterized in that the signal processor unit (40) 25 in use detects heat power which is absorbed by the sensor element (1 / 1,1 ', 1 ", 1" / 1 ^ 12,13, respectively). , 14,15,15) adjacent medium as a function of electrical power applied to the sensor element. System according to claim 3, 30, characterized in that the signal processor unit (40) in use detects heat power which is absorbed by the medium adjacent the temperature sensor (7,8,9) as a function of temperature sensed by each respective temperature sensor. System according to claim 1 or 2, characterized in that the signal processor unit (40) has 5 means for processing dynamic part and static part of a respective signal provided by a sensor element (1; 1,1 ', 1 ", 1 ", -1-1, 12,13,14,15,16), wherein the dynamic portion represents a characteristic decrease in electrical power supplied to the element as a function of time after effective coupling of the element to the signal processor unit (40). ), and where each static portion represents a stable power level consumed by the respective element after a stabilization period. System according to claim 3, 15, characterized in that the signal processor unit (40) has means for processing dynamic part and static part of a respective temperature signal provided by each of the temperature sensors (7,8,9), the dynamic part representing a characteristic decrease in temperature caused by 20 heat power absorbed by the respective medium at the position of the respective sensor as a function of time after effective coupling of the respective sensor to the signal processor unit, wherein the static portion represents a stable heat power absorption level consumed at the respective sensor after a stabilization period. System according to claim 1, 2 or 3, characterized in that the recording means (40, 41) have means for recording the dynamic behavior of the sensor element or the temperature sensor from the moment the element or sensor is switched on until a given time therefrom. deriving a composite function of values associated with the thermal properties of both the medium and the sensor element / temperature sensor, as well as means for correcting the measured values of thermal properties of the responsive element or sensor according to a calibration table for DK 169574 B1 22 so as to determine the thermal properties of the respective medium.