Apparatus for testing liquids quality in particular edible oil, cooking facility

FIELD: food industry.

SUBSTANCE: apparatus comprises sensor designed with at least one pair of separated electrodes. Sensor is drowned into liquid for measurements. Electrodes and liquid measured form capacitive element with capacity changing depending on dielectric permittivity of liquid measured. Basically electrodes reach the same plane, and liquid surrounds both surfaces of electrodes from any plane side. Electrode is attached to substrate in such a way that liquid flows through plane. Sensor generates a signal that provides assessment of liquid quality. Apparatus can be connected to any cooking facility.

EFFECT: reduction of parasitic insects influence on capacitive resistance of substrate at high temperatures.

50 cl, 7 dwg

The present invention relates to a capacitive device for measuring the quality and/or deterioration of the liquid, in particular oil. The invention concerns, in particular, devices of this type for measuring the quality and/or deterioration of edible oil, such as oil for frying, directly in the cooking device.

It is well known that the quality of edible oils is reduced during cooking, particularly when they re brought to high temperatures. As a rule, to cook food, these oils is brought to a temperature of approximately 180°C. At these temperatures there are many chemical reactions such as the polymerization reaction, thermal oxidation, etc. that change the quality of the oil. Some of the products of such reactions should not exceed some threshold value, through legislation, because outside of these thresholds oil is considered unfit for consumption. Thus, it is important to have the ability to detect thresholds indirectly, to replace the oil as soon as you will need to do this. For a long time, the determination threshold value left on the proportion of chefs who after checking through the organs of sight or smell was determined whether the oil is still usable on the I consumption. Of course, this method is purely subjective and therefore unreliable.

Various devices proposed in the prior art, up to the present time embody attempts to solve the problem, so you can objectively measure the quality and/or deterioration in the quality of edible oils. Since the deterioration of edible oils occurs, in particular, because of their thermal oxidation, and this reaction leads to the formation of polar compounds, the proposed device in which the degree of deterioration of oil quality is correlated with the dielectric constant of the oil by measuring the capacitance of the capacitor, which controlled the oil is dielectric.

Such a device is described, for example, in U.S. patent No. 5818731. This document reveals the essence of a device designed to measure the quality of edible oils and installed in the cooking device, such as apparatus for frying in deep fat (deep fryer). The proposed device provides simultaneous operational change control, capacity and transmission oils within a temperature range of cooking or frying. Capacitive measuring unit contains two sets of parallel plates, alternating with each other and limiting the measuring capacitor. When these sets of plates are immersed, Maslo, the latter becomes the dielectric of the measuring capacitor for the referenced block, and the capacitance change is measured by a bridge circuit resistance of the DC generator. However, this device has several disadvantages. The first drawback is that the gaps between the plates are small and that, when the plate is immersed in oil, the latter has no light leakage between the plates due to capillary phenomena. Therefore, it is not guaranteed constant oil changes present between the plates, which can lead to erroneous measurement results of deterioration of oil quality. Moreover, solid particles present in the oil, can also be trapped between the plates, which has a negative influence on the measuring signal. It should also be noted that when there is a small gap between the plates, the configuration of the capacitor, providing a parallel plate does not provide easy access to these intervals, which complicates the operations of maintenance of the device. Another disadvantage is that the capacitor plates are bulky and occupies a significant portion of space on the device for cooking. Moreover, only the measuring transducer formed by the capacitor is subjected to temperature changes that may is rivetti to erroneous measurements of capacitance, so the device needs to remedy such errors. The solution proposed in this document, is to use a temperature sensor that produces an indication in a suitable processing scheme, to take account of changes of the measured temperature using the software, enter data associated with controlled oil. Therefore, if the quality of the oil is changed, or if there is new oil, it is necessary to upgrade the software that makes the device inflexible in operation.

The main objective of the present invention is to overcome the disadvantages of the above known technical solutions through the development of an improved device designed to measure the quality and/or deterioration of the liquid by means of a capacitive measurement and having a simple, compact and inexpensive construction.

The present invention also is to develop a device of this type, in which the capacitive measuring sensor is designed to facilitate the flow of fluid, which is supposed to measure, in close proximity to its electrodes while maintaining a high level of sensitivity of the measuring changes in capacitance.

Task nastojasih the invention also consists in the fact, to develop a device of this type, which decreases the probability of capture of particles present in the fluid between the electrodes of the measuring capacitor.

Another objective of the present invention is to develop a device of this type, which facilitates maintenance, in particular the cleaning of the measuring sensor.

Another objective of the present invention is to develop a device of this type, in which the capacitive measurement is no longer dependent on temperature and is supported greater flexibility of use, i.e. the device, software processing schemes which do not require systematic modernization, when someone else wants to use the device with a liquid of a different nature.

The invention relates to a device for measuring the quality and/or deterioration of the liquid, in particular oil, and this device contains a sensor that includes at least one pair of electrodes spaced from each other, immersed in the liquid, which is supposed to measure, while the electrodes and the liquid form a capacitive measuring element, the capacitance of which varies depending on the dielectric constant of the liquid. The sensor is designed with the capability of issuing electric the definition of the output signal, showing the dielectric constant. The device additionally includes processing means, receiving the output signal and configured to determine the degree of quality and/or deterioration of the liquid on the basis of the output signal. This device differs in that the electrodes are essentially in the same plane, and the fact that the liquid washes both surfaces of electrodes on either side of the plane.

Thanks to these characteristics liquid, which is supposed to measure, can easily and quickly take place on either side of the electrodes of the capacitive measuring element. Thus, the liquid present in the immediate vicinity of the electrodes, it is possible to update that improves the reliability and accuracy of measurements performed using the device, since the latter reflect the evolution of water quality in General. This design also greatly reduces the risk of particulate matter in the air gap of the capacitive element. Another advantage of the device corresponding to the present invention is that an air gap is simple, and this facilitates maintenance operation of the sensor. It should also be noted that, as the fluid that bathes the surface of the measuring electrodes on either side of their median p is Ascoli, it is possible to achieve a high level of sensitivity of the measurements.

In accordance with a preferred embodiment of the invention, the sensor additionally includes a reference capacitive element containing at least one pair of reference electrodes, separated from each other, immersed in the sample liquid and the reference electrode and the reference liquid form of the reference capacitive element, the capacitance of which varies depending on the dielectric constant of the reference fluid, with reference capacitive element is designed with the capability of issuing a reference signal representing the dielectric constant of the reference liquid in the processing means, and processing means arranged to compare the output signal with the reference signal.

Thus, the reference capacitive element may be continuously measure the dielectric properties of the "new" or - in other words, the reference fluid having a not bad quality, and to submit the reference value of the dielectric constant for the liquid, which can be compared with the value of the dielectric constant, issued by the capacitive measuring element. The use of two sensors also addresses changes in the dielectric constant due to temperature changes. When the measuring device is associated with a cooking device, containing tank in which the oil for cooking, capacitive measuring element can be immersed in the oil in which to fry food, and this capacitive measuring element immersed in another reference edible oil, having the same characteristics as the oil for cooking, but is contained in the closed space isolated from the first oil.

In a preferred embodiment, the closed space containing the reference edible oil, is in thermal contact with the oil for cooking. Of course, the reference oil can be updated periodically, for example once a day, or - if necessary continuously to ensure a precisely defined reference value of the dielectric constant for oil, the quality of which is not deteriorated. This update can be performed automatically or manually.

Other characteristics and advantages of the present invention will be presented in the following description of preferred specific embodiments of the measuring device of the present invention, given as non-restrictive examples with reference to the accompanying drawings, on which:

figure 1 - schematic view of the first variant implementation of the measuring device corresponding to the invention;

figure 2 - schematic Popper is a great cross-section of the tank of a conventional device for cooking, attached to the measuring device shown in figure 1, the latter being partially shown in section along the line II-II corresponding to figure 1, and processing means not shown;

figure 3 is a graph showing depending on temperature, the capacitance of the capacitive element of the measuring device corresponding to the invention, when the capacitive element is submerged in the new oil and used oil;

4 is a schematic cross-section in the spatial image tank conventional device for cooking, is attached to the measuring device corresponding to the second variant embodiment of the invention;

5 is a variant of the second variant implementation of the measuring device corresponding to the invention;

6 is a variety of options exercise of the measuring device depicted in figure 5; and

Fig.7 is a possible implementation of the supporting structure for the capacitive elements of the device according to the invention.

Figure 1 shows the first variant of implementation is indicated as a whole by 1 position of the capacitive device for measuring the quality and/or deterioration of the liquid, in particular oil.

The following description will apply to the use of the device 1 for measuring the quality and/or deterioration of the quality of edible oils or similar substances, used for frying food in devices for cooking, containing tank in which the oil can be heated typically to a temperature of about 200°C.

The measuring device 1 includes a sensor 2, which includes a pair of electrodes 4, 6, separated from each other and immersed in the fluid F (2), for example in the oil for deep fryers, quality and/or deterioration in the quality you want to measure to determine whether it is suitable for use. The electrodes 4, 6 is formed with oil F capacitive measuring element EFM, the capacity of which varies depending on the dielectric constant of the oil. When oil quality deteriorates, the amount of polar compounds increases and causes an increase in the dielectric constant. Thus, by measuring the evolution of the capacitance of the capacitive measuring element EFM can determine the degree of quality and/or deterioration of the oil. Therefore, the sensor 2, and more specifically its capacitive element EFM made with the possibility of issuing an electrical output signal representing the dielectric constant of the oil in a wide temperature range, in particular between 20°200°C.

Each electrode 4, 6 pair has the form of a comb having a set of teeth 4A, 6A, essentially parallel to each other and extending from the base 4b, 6b. E is ktrade 4 and 6 are located relative to each other so the teeth 4A of the electrode 4 are interleaved with the teeth 6A of the other electrode 6 forming the interdigital configuration. Thus, the teeth of the electrodes 4 and 6 are essentially in the same plane.

The electrodes 4 and 6 are, for example, from the same plate, cutting it in a suitable manner, and this plate is rigid enough so that the electrodes could retain its shape during handling. In the described example, the electrodes are made of plate, consisting of steel, intended for the food industry (austenitic steel on the basis of carbon steel 18-10) and having a thickness in the range between 0.1 and 3 mm Can also use steel for the food industry related to other types, for example Z7CN18-09, Z3CND18-12-02, Z6CNDT17-12 and Z7CNU16-04. Plate cut by laser beam, and this ensures that between the teeth of the electrodes will create air gaps, the value of which is in the range between 10 nm and 1 mm, it is Clear that the smaller the air gap E, the greater the sensitivity of the capacitive element. In accordance with an alternative embodiment it is possible to provide for the fabrication of electrodes of a substrate covered with a conductive material, for example of a substrate coated with a layer of gold, platinum or similar material.

In the illustrated embodiment, implementation is tvline electrodes 4 and 6 are attached to the insulating substrate 8, which, together with guide means 10 holds the electrodes in a fixed position relative to each other. More specifically, each of the electrodes 4 and 6 are attached to the substrate 8 by means of the fastening tabs, protruding from their base 4b, 6b, using any suitable means, such as screws or similar fasteners. Orienting means 10 are, for example, positioning pins inserted into the substrate 8 and interacting with holes made with this purpose, the electrodes 4 and 6.

The substrate 8 has the shape of a frame with a Central opening 12, is located so that it applies to the area of the measuring electrodes 4 and 6, i.e. facing the air gap, the limited gaps between the teeth 4A of the electrode 4 and the teeth 6A of the electrode 6. With this configuration, the liquid, which is supposed to measure, in this case oil, is washed by the two front surface electrodes 4 and 6 on either side of the plane of the electrodes, so that it can circulate in close proximity to the teeth 4A and 6A of the electrodes 4 and 6.

Capacitive element EFM is surrounded by a metal frame CM. This metal frame forms a protective shield against external electrical interference and thereby reduce the impact of such interference during the measurement. This frame is typically formed by a metal grid.

is oblozhka 8 is preferably made of a material resistant to temperatures in the range between 20°200°and having a low coefficient of thermal expansion, for example of ceramic material. However, it can be made of any other insulating material compatible with the intended use of the measuring device. As an example of use in the food industry, in which a stable characteristic of the above-mentioned temperature range, the substrate 8 can be made of a fluorinated polymer such as Teflon.

To give an idea about the development of this idea were conducted final tests with the electrodes 4, 6, made of stainless steel, having a thickness of approximately 0.8 mm Electrode 4 contained 9 teeth, and the electrode 6 contained 8 teeth, which together limit 18 air gap of 100 μm each, and the teeth had a width of about 1 mm Substrate was made of a ceramic material and has a thickness in the order of 0.6 mm at the outer surface 5×5 cm².

The capacity of the capacitive measuring element EFM defined by the electrodes 4 and 6 together with the oil, was measured using the processing means 14 containing, for example, analog Converter 16 "capacity - voltage", well-known specialists in the field of technology associated with the microcontroller 18. In the quality of the ve example note that you can use manufactured by the company of xemics the Converter circuit "capacitance - voltage" model HE.

The electrodes 4 and 6 are connected to the input circuit 16, the output of which is issued analog signal S_Vvoltage, showing the capacity of the capacitive measuring element. The signal S_Vis input to the microcontroller 18, which converts the signal S_Vin the digital signal S_N. As a rule, use a microcontroller model NS, manufactured by Motorola. Digital signal available at the output of the microcontroller, are then fed to the display means 20, made for example in the form of a liquid crystal display or indicator on light-emitting diodes. The latter displays a numerical value that characterizes, for example, the dielectric constant of the oil. In accordance with an alternative implementation of this digital value can be processed accordingly to indicate the rate of polar compounds, measured in oil.

Figure 2 capacitive measuring element EFM measuring device 1 is placed in the tank 22 normal device 24 for cooking containing the oil to be tested. Processing means 14 and the indicator means 20 on this drawing is not shown. These means are, for example, in the case associated with the device is for cooking, but which is separated from the tank 22. Device for cooking, of course, is connected with a heating means which are not shown. In this embodiment, the capacitive measuring device svechina with hook means 26 attached to the substrate 8, with the upper edge of the side wall of the tank 22 and extends essentially parallel to the wall.

Figure 3 shows the curves C1 and C2, respectively, illustrating the change in capacitance With capacitive measuring element device 1 depending on the temperature T of the same oil, respectively, of the new exhaust. The term "waste oil" means oil that has undergone multiple cycles of cooking. Curve C1 shows the capacitance change of the capacitive measuring element when the electrodes 4 and 6 are immersed in the new oil, and the curve C2 shows the capacitance change of the capacitive measuring element when the electrodes 4 and 6 are immersed in the oil. It is noticeable that these curves, mainly evolve in the same way depending on temperature, in particular at a given temperature difference between the new oil and waste oil is essentially constant. Therefore, measurement of the capacitance of the capacitive element EFM simply ensures the establishment of differences between benign oil and atributa the essential oil within a wide temperature range.

In figure 4 we consider the second variant implementation of the measuring device corresponding to the invention, in which elements identical to the already described elements are denoted by the same positions. This device will also be described in the context of the use in the measurement of quality and/or deterioration of edible oil F contained in the tank 22 of the device 24 for cooking.

In this embodiment, the sensor 2 in addition to the capacitive measuring element EFM immersed in the oil, which is supposed to measure, contains a reference capacitive element EFR immersed in the reference oil F_FLbeing in an enclosed space separate from the oil, which is supposed to measure. Reference oil has the same features as the new oil, which is supposed to measure. The design of the reference capacitive element EFR preferably identical design capacitive measuring element EFM, although it is not necessary. Thus, the reference capacitive element EFR formed by the electrodes 4_FLand 6_FLtogether with the sample oil F_FL. Therefore, the reference capacitive element EFR made with the possibility of issuing a reference signal representing the dielectric constant of the reference oil and the signal can be compared with the change in enim output signal of the capacitive measuring element by using the processing means 26. The connection of the capacitive measuring element and the reference capacitive element with the handle means 26 is shown schematically in figure 4. In this example, the processing means 26 in a typical case contain a Converter 27 "capacitance - voltage" with three inputs and one output analog voltage connected to the microprocessor 28, which, in turn, is connected to the indicator means 30. The first electrode 6, 4_FLeach capacitive element EFM and EFR connected to the first common input of the Converter, and the second electrodes 4, 6_FLeach capacitive element EFM and EFR, respectively, are connected to second and third inputs of the Converter "capacitance - voltage". As an example, you can use the Converter 27 "capacitance - voltage" model GE manufactured by the company of xemics, and the microcontroller 28 of the same type as the one described in connection with the first embodiment.

In the illustrated embodiment, the reference capacitive element EFR and measuring capacitive element EFM located in the tank 22 of the device 24 for cooking. The reference capacitive element EFR is located in the enclosed space 32 and immersed in oil, which is supposed to measure, and the enclosed space 32 are sealed to ensure water resistance, so that the reference oil, terjadinya in it, not mixed with oil, which is supposed to carry out measurements that are in the tank 24. Measuring capacitive element EFM is enclosed in an open work space 34, the walls of which are formed, for example, grid, so that this element is immersed in oil, which is supposed to measure. The use of such walls causes the creation of a filter, which protects the measuring electrodes of the capacitive element EFM and thereby prevents the entry of solid particles suspended in the oil, in contact with the electrodes, which could interfere with the measurements. Of course, in accordance with another embodiment of these walls may not be.

Note that the walls of the enclosed space 32 and the walls of the open work enclosed space 34, respectively, form a protective metal frame or screen from external electrical interference that can reduce the impact of such interference during the measurement.

For reasons of convenience, enclosed space 32 and 34 are connected together and form a single structure 36, which is attached to the tank 22 of the device 24 for cooking. In the preferred embodiment, as shown in figure 4, the capacitive elements bonded with its substrate at its respective enclosed space of the insulating supports.

Enclosed space 32, the content is ASEE reference oil, contains the first channel 38, the hole can be sealed with a waterproof manner by means of a cap or cover (not shown). In accordance with a not shown variant enclosed space 32 may also include emptying means located in the lower part of this space.

Design 36 mainly located close to the inner vertical wall 22A of the tank, which leaves enough space for cooking during the measurement.

Structure 36 also includes at one of its lateral walls of the hook means 40A, 40b to interact with complementary means 42A, 42b attached to the wall 22A. In the illustrated example, the hook means 40 and a complementary hook means 42, respectively, contain two hooks 40A, 40b, 42A and 42b, interacting in pairs. Structure 36 also can be hung with the possibility of withdrawing inside the tank 22. Perform design 36 in the form of a removable node facilitates filling and emptying of the enclosed space 32 and maintenance operation of the capacitive elements EFM and EFR. Moreover, because the design of the 36 simple and, in particular, does not contain any moving mechanical parts, it is extremely reliable.

In this embodiment, the electrical connection between the two capacitance is time elements and processing means 26, located outside of the tank, are applied through the hooks 40A, 40b, 42A and 42b. Thus, the hooks 40A, 40b contain complementary pads 44a, 44b, respectively, are connected to the capacitive elements EFM and EFR. The hooks 42A and 42b contain complementary pads 46a, 46b, respectively, connected to the processing means 26 and intended for coming in contact with the pads 44a, 44b, when the structure 36 is suspended in the tank. The electrical connection between contact pads 44a, 44b and the capacitive elements is achieved by means of wires, missed ensuring water resistance through the wall of the enclosed space 32. Similarly, the electrical connection between contact pads 46a, 46b and processing is achieved by means of wires, missed ensuring water resistance through the wall of the tank 22. Of course, in accordance with one variant, the various connections between the capacitive elements and the processing circuit can be decoupled from suspend one of the tools in the tank 22, directly connecting them with a separate housing, which may contain or not contain the indicator means 30 and forms together with the construction of 36 - portable measuring unit, independent from any device for cooking.

Figure 5 p the cauldron variant of the second variant implementation of the measuring device, corresponding to the invention, where the device is connected with the system to update the reference oil. Updating the system contains a reservoir 48 containing the new oil and located outside of the tank 22. The tank 48 is communicated with the inlet of the enclosed space 32 through a pipe, which includes a pump P and the electromagnetic valve EV1. Enclosed space 32 is communicated through the outlet pipe, with an electromagnetic valve EV2 and opening into the tank 22.

The pump P and both solenoid valves EV1 and EV2 are preferably placed outside the tank 22, to escape the effect of temperature.

The pump P may be omitted in embodiments providing for the placement of the tank 48 is high enough to ensure that the oil, which is supposed to measure, was not raised in the enclosed space containing the reference oil, when the solenoid valve is opened.

This updates the system with the benefits associated with resources which are automatically programmable means for controlling the pump and solenoid valves. A system of this type facilitates the operation of the measuring device.

Figure 6 shows the variation of options exercise of the measuring device depicted in figure 5, the reservoir 48 informs who I am directly with the inlet hole enclosed space 32 through pipe 52. Enclosed space 32 is communicated through outlet pipe passing through one wall of the tank 22 and opening into the regeneration tank 50 located outside of the tank 22. The tank 48 is preferably in the form of a waterproof package, connected to the tube 52 by means of the knob 54A flow to drip feed and outlet of the enclosed space 32 also communicates with the controller 54b thread relating to the same type. Of course, the flow through both flow the same, and it can profitably be adjusted so that the volume of the enclosed space 32 will be updated daily. Another advantage of this alternative implementation is that the reference oil is continuously protected from exposure to oxygen.

The advantage of this type of proposed solutions is that there are no moving mechanical parts, which increases reliability and simplifies maintenance.

In the presence of the measuring device corresponding to the second variant implementation, the reference capacitive element immersed in the new oil, essentially at the same temperature, what is the oil, which is supposed to measure and which have a capacitive measuring element, guarantees due to the layout of BiH connecting elements, envisioning the Wheatstone bridge for resistance measurement), is the ability to distinguish changes in the dielectric constant of these elements caused by deterioration of the oil quality, from those options changes caused by temperature changes. The layout of the bridge of this type is described, for example, in the article entitled "Application of capacitance techniques in designing sensors" Willem Craisins ("Application of capacitance methods in sensor design" by Willem Chr. Heerens, published in J.Phys. E: Scientific Instruments 19: 897906 (1986).

In a variant implementation, described herein, can make various modifications and/or improvements obvious to experts in the art and are within the scope of the claims of the present invention defined by the attached claims. In particular, it is possible to provide the location of the capacitive elements in any orientation in the tank containing the liquid, which is supposed to measure.

You might also consider making a single design 36 in accordance with the configuration illustrated in Fig.7, which enclosed space 32 and 34 are smaller, and the walls of enclosed spaces on this drawing does not show to be seen capacitive elements EFM and EFR.

Of course, you can also be provided in the second embodiment, - the presence of the electrode, common to both capacitive elements to limit the number of connections.

Needless to say that just described measuring device corresponding to the invention is not limited to application to the measurement of parameters of edible oils and can be used to measure the quality and/or deterioration of any liquid, the evolution of the dielectric constant which shows the quality and/or deterioration of the liquid.

1. Device for measuring water quality, in particular edible oils, and the device includes a sensor immersed in the liquid, which is supposed to carry out measurements, the sensor includes at least one pair of electrodes spaced from one another and extending essentially in the same plane, and the electrode of each pair of electrodes is shaped ridge, with many essentially parallel teeth, and the teeth of one of the electrodes alternate with the teeth of the other electrode, forming an interdigital configuration, the electrodes and the oil form measuring capacitive element, the capacitance of which varies depending on the dielectric constant of the oil, and the sensor is designed with the capability of issuing an electrical output signal representing the dielectric constant,and processing means, receiving the output signal and configured to determine the degree of water quality on the basis of the output signal, with both sides of the electrodes immersed in the liquid on either side of the plane, at least the outer surface of each electrode, with the electrode attached to the substrate so that the liquid can flow passing through the plane.

2. The device according to claim 1, characterized in that the sensor additionally includes a reference capacitive element containing at least one pair of reference electrodes, separated from each other, and the reference capacitive element is designed for immersion in the reference liquid and the electrodes and the reference liquid form of the reference capacitive element, the capacitance of which varies depending on the dielectric constant of the reference fluid, with reference capacitive element is designed with the capability of issuing a reference signal representing the dielectric constant of the reference fluid in machining tools, and the fact that the processing means is arranged to compare the output signal with the reference signal.

3. The device po, characterized in that the electrodes of the reference capacitive element extends essentially in the same plane, and the fact that both sides of the electrodes of the reference capacitance is lementa submerged in the liquid on either side of their plane, so that fluid can flow, passing through the plane.

4. The device according to claim 2 or 3, characterized in that the reference fluid in the enclosed space, isolated from the liquid, which is supposed to measure, and in thermal contact with the latter, so that the reference fluid has essentially the same temperature as the liquid, which is supposed to measure.

5. The device according to claim 4, characterized in that enclosed space containing the reference fluid communicates with the system to update the reference liquid.

6. The device according to claim 5, wherein updating the system contains a reference liquid tank which is connected with means of flow control, providing regular updates of the reference fluid contained in the enclosed space.

7. The device according to claim 1, characterized in that the electrodes, respectively, are formed of flat plates.

8. The device according to claim 1, characterized in that the capacitive elements are surrounded by a metal frame forming a screen against electromagnetic interference.

9. The device according to claim 1, characterized in that the electrodes of the capacitive elements are made of steel for the food industry.

10. The device according to claim 1, characterized in that the electrodes of the capacitive elements mounted on an electrically insulating carrier is instrukcii, having an aperture opposite the region of the electrodes.

11. The cooking device, comprising a tank to contain liquid for cooking and heating means, characterized in that it additionally includes a device for measuring water quality for cooking, and the measuring device includes a sensor having at least one pair of electrodes spaced from one another and extending essentially in the same plane, and the electrode of each pair of electrodes is shaped ridge, with many essentially parallel teeth, and the teeth of one of the electrodes alternate with the teeth of the other electrode, forming an interdigital configuration, the electrodes and the liquid for cooking form measuring capacitive element, the capacitance of which varies depending on the dielectric constant of the fluid, and the sensor is designed with the capability of issuing an electrical output signal representing the dielectric constant, and processing means, receiving the output signal and configured to determine the degree of quality of the liquid for cooking on the basis of the output signal, with capacitive measuring element is located in the tank so that both sides of the electrodes immersed in the LM the bone for cooking on either side of the plane, so the liquid for cooking may be passing through the plane.

12. The cooking device according to claim 11, wherein the sensor additionally includes a reference capacitive element containing at least one pair of reference electrodes, separated from each other, and referred to the reference capacitive element is designed for immersion in the reference liquid and the electrodes and the reference liquid form of the reference capacitive element, the capacitance of which varies depending on the dielectric constant of the reference fluid, and the sensor is designed with the capability of issuing a reference signal representing the dielectric constant of the reference liquid, machining tools, and the fact that the processing means is arranged to compare the output signal with a reference signal.

13. The cooking device according to item 12, wherein the reference electrodes of the capacitive element extends essentially in the same plane, and the fact that both sides of the reference electrodes of the capacitive element is submerged in the liquid for cooking on either side of the reference plane of the electrodes.

14. The cooking device according to item 12 or 13, characterized in that the reference liquid is in a fenced area, from the new from the liquid for cooking, which is supposed to measure, and in thermal contact with the latter, so that the reference fluid has essentially the same temperature as the liquid for cooking, which is supposed to measure.

15. The cooking device according to 14, wherein the enclosed space containing the reference fluid communicates with the system to update the reference liquid.

16. The cooking device according to item 15, wherein updating the system contains a reference liquid tank which is connected with means of flow control, providing regular updates of the reference fluid contained in the enclosed space.

17. The cooking device according to claim 11, characterized in that the electrodes, respectively, are formed of flat plates.

18. The cooking device according to claim 11, characterized in that the capacitive elements are surrounded by a metal frame forming a screen against electromagnetic interference.

19. The cooking device according to claim 11, characterized in that the electrodes of the capacitive elements are made of steel for the food industry.

20. The cooking device according to claim 11, characterized in that the electrodes of the capacitive elements mounted on an electrically insulating supporting structure having an aperture rather the willows area of the electrodes.