EP2039223A2

EP2039223A2 - Hob allowing the temperature of a culinary article to be detected

Info

Publication number: EP2039223A2
Application number: EP07803856A
Authority: EP
Inventors: Jocelyn Bonnel; Noël BURAIS
Original assignee: SEB SA
Current assignee: SEB SA
Priority date: 2006-07-06
Filing date: 2007-07-06
Publication date: 2009-03-25
Also published as: JP2009543274A; FR2903564A1; FR2903564B1; JP5254966B2; CN101485231A; US20090314769A1; WO2008003872A2; WO2008003872A3; CN101485231B

Abstract

The invention relates to a hob (200) suitable for receiving a culinary article (100) and including a measurement system (203) which comprises means (220) for measuring the temperature of the article (100) and control means (240). According to the invention the measuring means (220) comprise an electrical circuit (219) possessing at least one inductive element (221) configured so as to induce a magnetic field on the article (100) which includes electrically conductive heat-sensitive means (130) that transmit a signal to the control means (240), the value of said signal being representative of the impedance (Z) of the circuit (119), the impedance being dependent on the resistivity (p) of the heat-sensitive means (130), and the control means (240) including at least one model corresponding to the thermal behaviour of this resistivity (P) and being configured so as to convert the value of the transmitted signal into a temperature.

Description

COOKING PLATE FOR DETECTING TEMPERATURE

A CULINARY ARTICLE

The present invention relates to the field of cooking plates, in particular those allowing the detection of the temperature of a culinary article. From a general point of view, it is a question of determining the temperature of a culinary article so as to optimize the cooking of a food, or to protect the cooking utensil, and this independently of the size of the article .

More specifically, the invention relates to a cooking plate adapted to receive a cooking utensil and comprising a measuring system which is adapted to measure the temperature of the culinary article, and which comprises measuring means and control means.

Such a plate is well known to those skilled in the art, in particular by the example given in the prior art document JP 5344926. This document describes a cooking system comprising a cooking utensil and a cooking plate. cooking. The culinary article is equipped with a thermosensitive means, and a secondary coil forming a closed circuit with the thermosensitive means. The cooking plate is provided with a primary coil, a high frequency generation means inducing a current in the secondary coil, and a temperature sensing means which determines the temperature of the cooking utensil according to the current level flowing in the primary coil.

The disadvantage of such a configuration is that it requires on the one hand to integrate a coil in the removable container, and secondly to position the secondary coil and the thermosensitive means inside. a protective case in the center of the upper face of the bottom of the container.

It is also known from DE 4413979. This document discloses a cooking system comprising a cooking utensil and a hob. The culinary article comprises at its bottom a sensor cooperating with a second sensor located in or on the hob. The sensor of the culinary article is essentially a multilayer ceramic sensor called "binary" to detect the achievement of target temperatures by abrupt modification of the dielectric constant at target temperatures. The cooking plate comprises a set of sensors, or electrodes, capacitively connected to the sensor dielectric located in the bottom of the cooking utensil.

The disadvantage of such a configuration is that it is dedicated to capacitive measurements and the measurement of the temperature is not fine because of the constraints of the target values. Finally, document US 2005/0258168 discloses a plate for grilling foodstuffs. This induction hob is provided with a tray on which are placed the food to be grilled, the tray being provided with a ferromagnetic material for the measurement of temperature.

The disadvantage of such a configuration is that it requires a particular steric arrangement for the positioning of inductive heating means and measuring means. In addition, it requires two measuring coils for a heating coil. The present invention aims to overcome these disadvantages by providing a simple device, easy to use and maintenance.

With this objective in view, the hob according to the invention, furthermore in accordance with the preamble cited above, is essentially characterized in that the measuring means comprise an electric circuit which has at least one element of inductive nature configured to inducing a magnetic field towards the culinary article and which transmits to the control means a signal resulting from the action of the induced magnetic field on electrically conductive thermosensitive means of the culinary article, the control means comprising at least one corresponding model the thermal behavior of the thermosensitive means, and being configured to convert the value of the transmitted signal into a temperature from the model.

Thus, the temperature of the culinary article can be measured accurately, since the resistivity varies continuously with temperature and this is more representative of the temperature of the food since it is directly on the food. culinary article and not on the cooking plate.

The measurement of the temperature can be performed during the heating of the culinary article by remote measuring means in the cooking plate without contact with the article. Thanks to the direct treatment by the electronics of the hob, it is not necessary to introduce this electronics (measurement, transmission ...) in a handle of the culinary article or to come to connect a probe of temperature in contact with the culinary article and the electronics of the plate. The regulation of the The temperature of the cooking utensil does not involve any signal transmission, in the sense that no means of infrared or radio communication is required between the cooking plate and the article. Furthermore, the temperature measurements made are discrete measurements whose frequency is advantageously periodic and can be chosen, or even modulated according to the temperature or the type of non-ferromagnetic material. Moreover, the culinary article can be used on any conventional type of heating means (induction, radian, gas, etc.), without risk of deterioration of the heat-sensitive means.

Other characteristics and advantages of the present invention will emerge more clearly on reading the following description given by way of illustrative and nonlimiting example and with reference to the appended figures in which:

- Figure 1 shows a cross section of a portion of a cooking system (in operation) comprising a -culinaire article according to an embodiment of the present invention and a cooking plate, the plate heating means cooking zone being in the heating state and the measuring means being in stop mode,

FIG. 2 is similar to FIG. 1, the heating means being in the off state and the measuring means in the induction mode, and

- Figure 3 shows the general principle of the evolution of the voltage in the measuring means and the current in the heating means. As can be seen in Figures 1 and 2, a cooking system 1 for cooking food includes a cooking utensil 100 adapted to receive food or a cooking fluid (water, oil ...), for example a pan or a 5, and a cooking plate 200 adapted to support the culinary article 100 and to transmit to the latter the energy required for cooking the food it contains.

As shown in FIGS. 1 and 2, the culinary article 100 comprises a base body 150 made from a thermally conductive base material, for example aluminum. This basic body generally defines the geometric structure of the culinary article and can serve as a support for a possible interior and / or exterior coating (enamel, paint, Teflon coating ...).

The culinary article 100 defines a receiving volume of the food to be cooked which is delimited by a bottom 101 and a side wall 102. The bottom 101 of the culinary article 100, here circular in shape, has

An inner face (or upper face) 110 intended to be in contact with food and an outer face (or lower face) 120 intended to be in contact with the cooking plate 200. At least a portion of at least one one of the faces 110, 120 of the bottom 101 has a substantially planar appearance, so as to ensure the stability of the culinary article 100 when it is placed on a horizontal surface (cooking plate 200, table, etc.). Here, the faces 110, 120 of the bottom 101 are entirely flat and the thickness of the bottom 101 is constant. Here, the bottom 101 is formed mainly by the material of the base body 150.

The culinary article 100 comprises heat-sensitive means 130 which conduct electricity. These heat-sensitive means are intended to enable the temperature of the culinary article 100 to be determined. Preferably, the material chosen for the heat-sensitive means 130 has a high variability of its p-resistivity over a given temperature range (preferably from ^20.degree. C at 300 ^° C.), which makes it possible to obtain precise temperature measurements. Moreover, in order to facilitate the calculations making it possible to determine the temperature, it is preferable that the variation of resistivity p as a function of the temperature (in the given temperature range) is linear, and, in order to obtain a high precision in the measurement of the temperature, that the temperature coefficient C _τ is high. Furthermore, preferably and for reasons explained later, the heat-sensitive means 130 are non-ferromagnetic means. For all these reasons, in the present embodiment, the heat-sensitive means are made of titanium.

The heat-sensitive means 130 are integrated in the bottom 101 of the culinary article 100. In the present embodiment, the heat-sensitive means 130 have a constant thickness. Here, the heat-sensitive means 130 are formed by a thermosensitive element 130 (an insert integrated in the base body 150). Preferably and for reasons explained later, the heat-sensitive means 130 (here, a face of the insert 130) constitute a part of the outer wall 102 of the bottom 101 of the culinary article 100 (here the central portion), as shown in Figures 1 and 2.

In the present embodiment, the heat-sensitive means 130 have a symmetrical shape of revolution whose axis S is perpendicular to the plane of the bottom 101. In this case, the insert 130 has the appearance of a disk which is concentric with the bottom 101 of the culinary article 100.

On the other hand, in the present embodiment, as illustrated in FIGS. 1 and 2, the culinary article 100 also comprises ferromagnetic means 140. These ferromagnetic means 140 are intended to allow the heating of the food when the cooking plate 200 on which rests the culinary article 100 is a magnetic induction plate, and they are configured to transform an incident magnetic field (shown in Figure 1 by field lines 211) from the hotplate 200 into heat, by Joule effect (induced by eddy currents). In this embodiment, the ferromagnetic means 140 are integrated ^"in" Ie ^ -Wallpaper 101 "de the culinary article 100, and more precisely in the main body 150. In this embodiment, the ferromagnetic means 140 extend in a ring 140. They may be, for example, in the form of a grid or hot-glued capsules.

According to the invention, the heat-sensitive means 130 and the ferromagnetic means 140 are arranged relative to each other so that the heat generated by the ferromagnetic means 140 is transmitted by thermal conduction to the heat-sensitive means 130. Here, the crown 140 in ferromagnetic material is in contact with the circular insert 130 of thermosensitive material which it surrounds.

As shown in Figures 1 and 2, the cooking plate 200 includes a receiving surface 201 adapted to receive the culinary article 100 (more specifically, the lower face 120 of its bottom 101). The cooking plate 200 comprises at least one focus (in this case, only one).

The cooking plate 200 comprises a heating system 202 and a temperature measuring system 203. The heating system 202 comprises heating means 210 and regulating means 230. At each hearth are associated heating means 210 which are clean .

The regulation means 230, for example a microcontroller and its adapted program, allow, for example, the regulation of the heating means 210 around a setpoint, or the triggering of a timer, etc.

In the present embodiment, as shown in FIGS. 1 and 2, the heating means 210 are inductive. For this purpose, they comprise an inductor, in this case an inductive heating coil 210. Each focal point comprises at least one inductive heating coil 210 (in this case, only one). Furthermore, the cooking plate 200 comprises first thermal protection means which make it possible to thermally protect the heating means 210 when they are inductive.

In the present embodiment, the heating system 202 is configured so that the heating means 210 provide a sequenced heating over time and pass successively and alternately in a heating state in which they generate and transmit the cooking energy, and in a state of stopping in which they no longer generate this energy. In this case, the heating means 210 being inductive, they are powered by an alternating current of frequency f _x modulated in amplitude by a frequency f ₃ , the zero (and the adjacent area as explained below) of the corresponding modulation in the off state and the rest in the heating state. A typical ± χ frequency is, for example, 18 to 25 kHz. A typical modulation frequency is f ₃ equal to 50 Hz or 60 Hz (100 Hz or 120 Hz after rectification).

The temperature measuring system 203 comprises measuring means 220 and control means 240.

The measuring means 220 comprise an electrical circuit 219 having at least one element of inductive nature 221, regardless of the nature (inductive or not) of the heating means 210. In the present embodiment, the element of inductive nature is a inductor 221, in this case, an inductive measuring coil 221. As can be seen in FIGS. 1 and 2, the inductive measuring coil 221 is disposed at the center of the induct-heating coil 210. ^~ • -. ^~ ---

The magnetic field (shown in FIG. 2 by field lines 222) generated by the inductive measurement coil 221 is of much smaller amplitude than that generated by the inductive measuring coil 210 and does not make it possible to heat a ferromagnetic material by induction.

The inductive measuring coil 221 makes it possible to measure by induction the intensity of the current flowing in the thermosensitive element 130 of the culinary article 100 when it is positioned on the receiving surface 201. Indeed, the inductive measuring coil 221 is comparable to the primary circuit of a transformer while the heat-sensitive means 130 of the culinary article 100 are the secondary circuit.

The principle of the measurement is based on the variation of the impedance Z of the electrical circuit 219 (in this case an RLC circuit comprising the measurement inductive coil 221 and a capacity capacitor C connected in series with the inductive measuring coil 221. ) as a function of the variation of the temperature of the temperature-sensitive elements 130. The measuring coil 221 is characterized by an inductance L _B (whose variation as a function of the temperature is sufficiently low to be neglected) and a resistor R _B. The value of the impedance Z of the electrical circuit 119 (primary circuit) is a function of the resistance R _B of the inductive measuring coil 221 (whose value is known) and of the resistor R ₃ of the secondary circuit formed by the heat-sensitive material 130 (whose value depends on the temperature). The values of the voltage U applied to the electrical circuit 119 and of the impedance Z correspond to the intensity I of the current flowing in the inductive measurement coil 221, according to the relation U = Z * I.

The measurement of the intensity of the current I flowing in the inductive measuring coil 221 makes it possible to determine the impedance Z of the electrical circuit 119 and therefore the resistance R of this circuit 119, to deduce the resistance R _s from them. thermosensitive means 130 and therefore their resistivity p (the dimensions of these means being known) and their temperature.

The control means 240 make it possible to determine the temperature of the culinary article 100 from the measurement of the intensity I of the current flowing in the measuring inductive coil 221, the measuring means 220 transmitting towards the control means 240 a signal of which the value is representative of the impedance Z of the circuit 119 (in this case, the intensity I of the current flowing in the inductive measuring coil 221).

The control means 240 comprise at least the model of the thermal behavior of the resistivity p of the thermosensitive material 130 inserted into the bottom of the culinary article 100. It is easy to understand that the use of thermosensitive means 130 with a temperature coefficient C _T constant (actually or according to an acceptable approximation) in the operating temperature range of the culinary article 100 makes it possible to greatly facilitate the determination of the temperature from a value of the resistivity p, the model then being linear . In order to achieve this determination, the control means 240 advantageously comprise a microprocessor.

In order to facilitate the determination of the temperature (more precisely, in order to facilitate the correlation between the variation of the resistance R and the intensity I), it is advantageous for the inductive measuring coil 221 to be

- "• powered by a voltage U - {- in this case, -a-slot voltage) whose frequency f ₂ corresponds to the resonance frequency f _r of the electrical circuit 119 which is equal to

1 / (2Π / L _B .C): at this frequency, the impedance Z of the electrical circuit 119 is equal to its resistance R, and the applied voltage U and the intensity I in this circuit 119 are proportional (U = R * I). In fact, the capacitor C is chosen as a function of the supply frequency f ₂ and the inductance L _B of the inductive measurement coil 221. The inductive measurement coil 221 thus makes it possible to measure a variation of resistance R. who can be correlated with a temperature variation of the culinary article 100.

Furthermore, the resistance R ₃ of the temperature-sensitive means 130 depends inter alia on the penetration depth δ of the magnetic field created by the inductive measuring coil 221, and this penetration depth δ depends both on the resistivity p and on the permeability magnetic means μ _r of the thermosensitive means 130, according to the formula δ = / (p / π · μ _o · μ _r · f), where μo is the magnetic permeability of the vacuum and f is the frequency of the inductive measuring coil 221 ( here, f ₂ ). However, if these two properties δ and μ _r vary at the same time, it is extremely difficult to connect the variation of the resistance R measured by the inductive measuring coil 221 (in fact the intensity I) to the temperature of the article. Culinary 100. Therefore, it is easily understood that it is very advantageous that the heat-sensitive means 130 are non-ferromagnetic, the magnetic permeability μ _r then being comparable to 1 and not dependent on the temperature, unlike a ferromagnetic material. In fact, once the nature of the non-ferromagnetic material of the heat-sensitive means 130 has been determined, their thickness E is chosen as a function of the frequency f ₂ of the supply voltage U of the inductive measuring coil 221. so as to be greater than the penetration depth δ associated with this frequency f2. Conversely, the frequency f ₂ of the supply voltage U of the measuring inductive coil 221 can be determined as a function of the thickness E of the heat-sensitive means 130 and the desired penetration depth δ. In the present embodiment, the means thermosensitive 130 non-ferromagnetic titanium have a thickness of 1.2 mm for a frequency f ₂ of 5OkHz.

Another advantage of using as a thermosensitive means 130 a non-ferromagnetic material is that, in this case, the inductance L _B (known) of the inductive measuring coil 221 varies little in its presence.

Thus, in this particular case, the only variable element as a function of the temperature in the impedance Z of the circuit 119 is the resistivity p of the heat-sensitive means 130 (and therefore the sole property of the thermosensitive means 130 to intervene in the measurement of the Temperature when they are made in a non-ferromagnetic material is the variation of their resistivity p), which makes it easy to obtain an accurate measurement. In order to improve the measurement, the thermosensitive means 130 are advantageously positioned vis-à-vis the measuring inductive coil 221. In addition, the surface of the thermosensitive means 130 is preferably greater than that of the inductive measurement coil 221. , which increases the reliability of the measurement.

So far de_ ^"temperature of the culinary article 100 is done independently of the heating of the article, and can take place as soon as it is placed on the hob 200, without any activation of the means 210, and regardless of the size of the culinary article 100.

Furthermore, in the present embodiment, the cooking plate 200 comprises second thermal protection means which make it possible to thermally protect the measuring means 220. These second thermal protection means may be either specific or constituted by the first means thermal protection. In the present embodiment, since the heating means 210 are inductive, so as not to disturb the measurement of the temperature of the culinary article, this is preferably done around the zero crossing of the modulation of the supply current of the heating means 210, so as to avoid induction phenomena between the heating inductive means 210 and the measuring inductive means 220, even if the respective frequencies f ₁ , f ₂ are preferably substantially different (the frequency

10 may be different or not).

For this purpose, and in order not to be damaged, the inductive measuring coil 221 in operation, successively and alternately passes in stop mode in which it is powered by a zero voltage (circuit

15), and in induction mode in which it is powered by the pulse voltage U of frequency f ₂ ) • FIG. 3 represents, for the same arbitrary time unit, the evolution of the voltage across the coil inductive measurement 221 at a frequency f ₂ and 0 the evolution of the modulated current in the inductive coil of

-2-10 heating at a frequency modulated by a frequency f ₃ -

This figure schematically and simulated mainly illustrates the differences between the frequencies fi, f ₂ 5 inductive coil heater 210 and measuring 221, and in that the inductive measuring coil 221 is supplied that the vicinity of the passage at zero of the modulation of the current of the inductive heating coil 210. 0 In the present embodiment, contrary to Figure 3 representing the principle of operation, around the zero crossing of the modulation, when the voltage of the inverter generating the modulation frequency f ₃ falls below a certain limit (for example 30-40V), the latter (by construction) stops (the arcs of the modulation are not as regular as in FIG. ). Therefore, there is a time (one to two milliseconds for a 50 Hz modulation) around the theoretical zero crossing of the modulation where the field of the induetive heating coil 210 is zero and therefore where the heating means 210 are in their stopping state. This time is sufficient to perform the measurement.

In the preferred embodiment, the cooking plate 200 comprises complementary measuring means (not shown) suitable for measuring the temperature of the receiving surface 201, for example means of the CTN type (means whose electrical resistivity is a function of a Negative Temperature Coefficient). These complementary measuring means (conventionally used in the cooking plates 200) are connected to the temperature measurement system 203 (and more particularly to the control means 240) and make it possible to correlate the measurement made by the inductive coil of measurement 221. The temperature comparison may take place only at the beginning of the heating of the culinary article 100 or at the beginning of the heating of the culinary article 100 or any time during this heating.

The detection of a temperature by the inductive measuring coil 220 and / or by the complementary measuring means also makes it possible to determine the attainment of a maximum target temperature generating a heating stop and thus protecting the culinary article 100. In use, in the present embodiment, the culinary article 100 is positioned on the induction hob 200. Following activation of the heating means 210, for example by selecting a function or a program (simmering, boiling water, cooking with oil, cooking without fat, etc.), the inductive heating coil 210 produces a magnetic field which induces currents in the ferromagnetic means 140 of the bottom 101 of the culinary article 100, which, by the Joule effect, heats these ferromagnetic means 140 and, by thermal conduction, the rest of the culinary article 100 , including the thermosensitive insert 130.

With the variation of temperature, the resistivity p and the resistance R _s of the heat-sensitive means 130 change, as well as the resistance R and the impedance Z of the electrical circuit 119. Due to the use of a non-ferromagnetic material as a heat-sensitive medium 130 and the supply of the inductive measuring coil 221 by a voltage U whose frequency f ₂ corresponds to the resonance frequency f _r of the electric circuit 119, the intensity I sent by the measuring means 220 to the means of - control

240 allows the latter to easily determine the temperature of the culinary article 100 from this intensity I. Furthermore, the temperature measurement system 203 can also be used for other functions such as the detection of the presence of a culinary article 10 on the cooking plate 200, or even its centering, or the recognition of the type of culinary article 100 or its compatibility with the cooking plate 200, combined for example with the generation of an error signal or inhibiting the heating means. Indeed, the presence a metal material in the vicinity of the measuring means 220 changes the impedance of the circuit 119, and this change is translated by the control means 240 without necessarily converting this impedance change temperature.

The present invention is not limited to the present embodiment.

Regarding the bottom of the culinary article, it is possible that its faces have a slight concavity, that its thickness is not constant, that its shape has an appearance other than circular, for example an oval or rectangular (square).

With regard to the material used for producing the heat-sensitive means, it is possible to use metals such as titanium, bismuth, molybdenum (in particular molybdenum silicon MoSi2), platinum, copper, aluminum, magnesium, zinc or nickel, or alloys. of these metals or metal ceramics, austenitic stainless steel or non-ferrous enamels. Regarding the heat-sensitive means, they may have another ^'-forma .qu'un ^disc', for example forming an assembly comprising at least one ring or a sum of concentric rings with the bottom center of the cooking utensil and preferably connected thermally between them. They may have a relief or cutouts (preferably, the cuts are located in the plane of the bottom of the culinary article). They may also, at least in part, be covered with a material transparent to a magnetic field, such as an enamel or a paint, which forms at least part of the bottom face of the bottom of the culinary article which allows to the culinary article of power be easily cleaned without risk of deterioration of the heat-sensitive means.

The heat-sensitive means may not form an insert, but may be deposited in the form of a layer (s), for example by screen printing or thermal spraying. They can also be formed by several superimposed non-ferromagnetic materials, for example rolled or layered.

As regards the ferromagnetic means, they may be remote from the heat-sensitive means as long as the heat-sensitive means are not thermally insulated.

Regarding the hob, it could include several homes, each of which is respectively equipped with a measuring coil. In this case, the cooking plate may comprise only one measuring system for all the hearths, connected by multiplexing to the different measuring coils of the hearths.

With regard to the control means, these may comprise several models of thermal behavior,

20 each model corresponding to a heat-sensitive material

: ^•• - -Give of sor-te increase flexibi-1-ity d_ 'util-i-sation-'de the hob. In addition, a thermal behavior model may include several thermal behavior patterns for a plurality of measurement frequencies, which

25 which then allows to recognize the thermosensitive material of the culinary article. In addition, the control means could be coupled with the control means, for example in the form of an electronic circuit, or integrated together in a microprocessor.

With regard to the measuring system, the supply voltage of the measuring means can be in the form of of a multifrequency excitation, or in the form of pulse (s) of Dirac.

In order to have a measurement of the temperature around at least one zero crossing of the modulation of the current, especially if the time of the determination of the temperature is relatively long, it is possible to measure every N zero crossings of the modulation, with N natural integer (eg every five or ten seconds with a 50 Hz modulation) and stop the inverter during an ark (half a period) so as to have a zero current in the inductive heating coil without disturbing the heating of the article.

Claims

1. A cooking plate (200) adapted to receive a cooking utensil (100) and comprising, on the one hand, a heating system (202) which comprises heating means (210) and, on the other hand, a system measuring device (203) which is adapted to measure the temperature of the cooking utensil (100), and which comprises measuring means (220) and control means (240), characterized in that the measuring means (220) ) comprise an electrical circuit (219) which has at least one inductive element (221) separate from the heating means (210) and configured to induce a magnetic field towards the culinary article (100) comprising heat-sensitive means (130) electrically conductive whose resistivity (p) varies with temperature, the electrical circuit (219) transmitting to the control means (240) a signal whose value is representative of the impedance (Z) of the circuit (119) depending on the resistivity (p) of the heat-sensitive means (130) of the it of the action of the magnetic field induced by the element of inductive nature (221) - said measuring means (220) on these thermosensitive means (130), the control means (240) comprising at least one model corresponding to the behavior thermal resistivity (p) thermosensitive means (130), and being configured to convert the value of the transmitted signal into temperature from the model.

2. Cooking plate (200) according to claim 1, wherein the magnetic field generated by the element of inductive nature (221) measuring means (220) does not allow to heat a ferromagnetic material by induction.

Cooking plate (200) according to any one of the preceding claims, characterized in that the signal transmitted to the control means (240) is the intensity (I) of the current flowing through the inductive element (221). said measuring means (220).

4. Cooking plate (200) according to any one of the preceding claims, characterized in that the inductive element (221) of said measuring means (220), in induction mode, is powered by a voltage ( U) whose frequency (f ₂ ) corresponds to the resonance frequency (f _r ) of the electric circuit (119), said electric circuit (119) being provided with a capacitor.

Cooking plate (200) according to claim 4, characterized in that the capacitor of the electric circuit (119) is connected in series with the inductive element (221) of said measuring means (220).

Cooking plate (200) according to one of the preceding claims, characterized in that the electrical circuit (119) is configured so that the signal transmitted to the control means (240) depends only on the resistivity ( p) thermosensitive means (130) when the latter are non-ferromagnetic.

7. Cooking plate (200) according to one of the preceding claims, characterized in that the electric circuit (219) is configured so that the penetration depth (δ) of the magnetic field induced by the element of inductive nature ( 221) of said measuring means (220) is smaller than the thickness (E) of the heat-sensitive means (130) of the cookware (100) compatible with the cooking plate (200).

8. Cooking plate (200) according to one of the preceding claims, characterized in that the element of inductive nature (221) of said measuring means (220), in operation, passes successively and alternately in induction mode in which it is powered by a voltage (U), and in stop mode in which it is not powered.

Cooking plate (200) according to claim 8, characterized in that the heating system (202) is configured so that the heating means (210) generates the energy to the cooking utensil (100) so that sequenced in time, and cooperates with the measuring system (203) so that the element of inductive nature (221) of said measuring means (220) is in induction mode when the heating means (210) are in shutdown state and is in stop mode when they are in heating state.

10. Cooking plate (200) according to claim 9, characterized in that the heating means (210) are of inductive nature and are powered by an alternating current amplitude modulated, the zero of the modulation corresponding to the state of stopping the heating means (210) and the rest in the heating state.

11. Cooking plate (200) according to claim 10, characterized in that the inverter generating the modulation stops when its voltage falls below a minimum value.

12. Plate according to claim 10 or 11, characterized in that the inverter generating the modulation is stopped regularly every N zero crossings of the modulation for half a period of the modulation.

Cooking plate (200) according to one of the preceding claims, characterized in that comprises complementary measuring means adapted to measure the temperature of the receiving surface (201) of the cooking plate (200) on which the cooking utensil (100) rests and connected to the measuring system (203) so as to calibrate this last.

14. Cooking system (1) adapted to cook a food, characterized in that it comprises a cooking plate (200) according to one of claims 1 to 13, and a culinary article (100) whose bottom ( 101) comprises heat-sensitive means (130) made of electrically conductive materials whose resistivity (p) varies with temperature.

15. Cooking system (1) according to claim 14, characterized in that the cooking plate (200) is in accordance with claim 6 or one of the claims dependent thereon, the heat-sensitive means (130) of the culinary article (100) being made of non-ferromagnetic materials.

16. Cooking system (1) according to claim 14 or 15, characterized in that the cooking plate (200) is in accordance with claim-7 or one of the claims, which depends on it, the thickness (E ) thermosensitive means (130) of the culinary article (100) being greater than the depth of penetration (δ) of the magnetic field induced by the inductive element (221) of said measuring means (220) of the cooking (200).

17. Cooking system (1) according to one of claims 14 to 16, characterized in that the cooking plate (200) is in accordance with claim 10 or one of claims dependent thereon, the culinary article (100) comprising ^{ferromagnetic} means (140) arranged by to the heat-sensitive means (130) so as to transmit to them the heat they produce under the effect of the magnetic field induced by the heating means (210) of the cooking plate (200).

18. Cooking system (1) according to one of claims 14 to 17, characterized in that the cooking plate (200) comprises at least one hearth with which is associated an element of inductive nature (221) of said measuring means ( 220), the heat-sensitive means (130) being arranged in the bottom (101) of the culinary article (100) so as to be opposite said element of inductive nature (221) when the culinary article ( 100) is arranged on the hearth.

19. Cooking system (1) according to claims 17 and 18, characterized in that the ferromagnetic means (140) are arranged in the bottom (101) of the culinary article (100) so as to be vis-à- screw heating means (210) of inductive nature when the culinary article (100) is disposed on the hearth.

20. Cooking system (1) according to claim 19, characterized in that, for each home, an inductive element (221) of said measuring means (220) is surrounded by the heating means (210) of inductive nature .