Patent Publication Number: US-2023137254-A1

Title: Sensor means or module for determining a displacement or deflection or bending, household appliance and method for determining the weight of an item

Description:
The present invention relates to a sensor means or module for determining a displacement or deflection or bending, in particular an elastic displacement or deflection or bending, of a panel or of a section thereof or of an insert in relation to the panel. The present invention further relates to a household appliance, in particular a cooking hob, more in particular an induction cooking hob, comprising an at least approximately horizontal panel. Finally, the present invention relates to a method for determining the weight of an item on an at least approximately horizontal panel of a household appliance, in particular on a top plate of a cooking hob. 
     For a proper treatment of items in households it may be beneficial to know the weight of the items. For example, an overloading of the oscillating system in washing machines can be avoided if the user knows the actual loading condition of the introduced laundry. Further, the dosage amount of a detergent can be adjusted to the laundry loading. In the field of food preparation, a weighing unit or device integrated in or allocated to a cooking hob or an oven can assist the user in precisely adding amounts of ingredients to the food, even after start of the cooking process or already during the preparation process to make the food ready to be cooked, and there is no need for an extra kitchen scale taking up space of the kitchen worktop. 
     From DE 199 26 513 A1 a cooking hob with a scale unit is known. The cooking hob comprises a glass top plate and a detection unit, which identifies a deformation of the top plate as a result of the weight load of a cooking vessel and determines the related weight. The detection unit includes a bending bar and dedicated strain gauges, the latter being connected to a processing circuitry for the interpretation of the signals of the strain gauges. 
     It is an object of the present invention to provide a sensor means or module, a household appliance and/or a method for determining the weight of an item, which further improve weight determination of items by means of measurement technology relying on a displacement or deflection or bending of a panel. 
     The object is achieved for the sensor means or module for determining a displacement or deflection or bending of a panel or of is a section thereof or of an insert in relation to the panel according to the features of claim  1 . 
     According to a first aspect of the invention, a sensor means or module is provided for determining a displacement or deflection or a bending of a panel, in particular a glass or glass ceramic panel, or of a section of a panel or of an insert in relation to the panel. Said displacement or deflection or bending, which is particularly an elastic displacement or deflection or bending, may be any kind of dislocation of the whole panel in relation to its original or regular position or alignment, particularly its planar alignment, or of only a section of the panel in relation to the other section or sections, which remain(s) unaffected. Also a dislocation of an insert part or insert component in relation to the panel, which is particularly an unaffected panel, may be covered. The expression “determining a displacement or deflection or bending” may be understood as a pure detection of the existence of such kinds of dislocations or as an estimation or an exact measuring of the value or level thereof. The sensor means or module and the panel or said section thereof form a weighing means, in particular a weighing scale. The sensor means or module is adapted to be integrated in or allocated to a household appliance and comprises or is connected to at least one processing and/or interpretation and/or compilation means, which may provide for a particular high sensor sensitivity and/or evaluation unit accuracy. The household appliance may be a cooking hob, in particular an induction cooking hob, and said panel, specifically said glass panel, may be a top plate comprising at least one cooking zone. 
     The sensor means or module may be or may comprise a photosensor for measuring a distance to a surface of the panel. A reference point or a reference area may be defined on the panel for the distance measurement. The photosensor is preferably positioned underneath the panel. Moreover, the photosensor may be a photointerrupter. With this type of sensor specifically small surface movements, occurring in the case of glass displacement or deflection or bending, of about 0.01 to 0.3 mm are detectable and measurable. Photointerrupters usually show a high resolution in the distance between 0 and 0.5 mm. 
     According to a specific embodiment, the photosensor is a reflective type photosensor and the reference point or reference area for the distance measurement comprises a reflection surface. Said reflection surface is preferably a shiny surface, particularly a shiny metallic surface, of the panel. The reflection surface may also be a printed glass surface, particularly a glass surface with a metal evaporation. Finally, it may be a surface of a drop of a colour or print, particularly a white colour drop, applied on the panel surface, in particular facing the photosensor. 
     The sensor means or module, in particular the photosensor, may be arranged or arrangeable distant from the panel, which arrangement may be favourable for a precise distance measurement. An advantageous arrangement is performed at a housing or a frame part of the household appliance or of a component or module arranged inside of the household appliance. In a preferred embodiment, the photosensor is applied on a printed circuit board, which is particularly connected to or fixed to the housing or to the frame part. 
     In addition or as an alternative to the above-described embodiment comprising a photosensor, an acceleration sensor for a detection of an acceleration of the panel section or of a panel reference point or reference area during the, particularly elastic, displacement or deflection or bending of the panel section or the panel reference point or panel reference area due to a is placing of an item to be weighed on the panel may be provided. Said reference point or reference area may be located on a panel surface. Said acceleration sensor may at least be adapted to detect the incidence of an acceleration and consequently a downward deflection of the panel section or panel reference point or area. It may be possible to determine the duration of the acceleration and a reverse point or time of a potential overshoot until the panel becomes stationary in a deflected or bent condition. 
     Advantageously, the sensor means or module comprises calculation means for an estimation of the displacement or deflection or bending of the panel section or the panel reference point or panel reference area by integration of the acceleration or of the accelerated movement, preferably integration over time. With said integration the value or intensity of the deflection or bending, particularly after finalization of overshooting and stabilization in the deflected or bent condition, may be exactly calculated. Further, having determined the value or intensity of deflection or bending, an approximate weight estimation may be performed by means of a database, particularly of a look-up table comprised therein. 
     A further additional or alternative embodiment of the sensor means or module is characterized by at least one strain gauge and/or extensometer, which is placed on or allocated to a bottom surface of the panel and which is adapted to determine the value of a length extension of the bottom surface during the downwards deflection or bending of the panel. Said embodiment may be further characterized by a Wheatstone bridge circuit for the estimation of a strain resistance corresponding to the strain level or the value of a length extension. Said length extension may be measured in at least one arbitrary direction, at least when the at least one strain gauge and/or extensometer is positioned in a is centre area of the panel. 
     Preferably, at least a second strain gauge may be oriented in at least a second direction in order to improve the measurement. In the case of more than one strain gauge, a provision of a corresponding number of Wheatstone bridges may be considered, but it may be generally sufficient to provide a modification of the configuration of the (one) Wheatstone bridge accordingly. 
     In order to further improve evaluation accuracy, an amplifier may be allocated to or connected to the sensor means or module, in particular to the strain gauge and/or to the extensometer and/or to the Wheatstone bridge circuit. As above, if in the case of more than one strain gauge a corresponding number of Wheatstone bridges should be considered, then also the number of amplifiers may correlate with the number of strain gauges and/or extensometers and/or Wheatstone bridges. However, as mentioned above, since in said case of at least two strain gauges the provision of an only modified Wheatstone bridge is generally sufficient, in this constellation there is also no need for providing more than one amplifier. 
     In a preferred embodiment, the sensor means or module comprises a specifically increased bridge voltage of the Wheatstone bridge circuit, which can be a further measure for a further improved evaluation accuracy. Typically, the bridge voltage, which is also named as “excitation voltage”, may have a value of 5V or 12V. The sensitivity of the bridge is strictly related to the voltage value, therefore, if the sensitivity will be not sufficient, the excitation voltage will be increased accordingly. Another course of action could be to provide for a specifically increased gauge factor of the strain gauge, the gauge factor preferably being greater than 2. Many different strain gauge types are available, in particular differing in the material they are made of. Their gauge factors may be within a range of 2 (for a cheap solution) to around 16 (for more expensive solutions). Finally, also a low noise amplifier and/or a rail to rail amplifier and/or a high gain instrumentation amplifier may be used in addition or alternatively for the desired accuracy. 
     Yet another further additional or alternative embodiment of the sensor means or module provides the insert, which is displaced or moved in relation to the panel under the weight of an item to be weighed, for being a, preferably removable, cover part or lid of a downdraft device or system in or allocated to a household appliance. Said cover part or lid is particularly an element of a downdraft cooking hob. 
     In particular, the sensor means is arranged between the cover part and a collar for supporting the cover part, wherein the collar is arranged at the panel and forms an upper frame of a filter element or a filter inlet. Specifically, the sensor means is coupled with the cover part or with the collar. 
     In order to enable a removal and/or an exchange of said sensor means and/or of said cover part, magnetic and/or adhesive elements or other fixing elements or means may be comprised for an adherence of the cover part at the panel, particularly at said collar, and/or of the sensor means at the cover part or at the collar. 
     Preferably, the sensor means comprise multiple single sensor elements, preferably a number of between two and six, more preferably between two and four, spaced apart from each other on a circle, the number of single sensor elements particularly being subject to an equal weight load. A provision of three single sensor elements, which are arranged on the corners of an equilateral triangle, may provide a particular equability of weight distribution, since the cover part or lid will uniformly rest on said evenly spread single senor elements. Alternatively, four single sensor elements may be provided in the corners of a rectangle, particularly of a square. The provision of more than only one single sensor element may end up in an increased precision of weight determination, in particular by a comparison of the single weight measurements. On the other hand, the more single sensor elements will be provided, the higher the costs for the total arrangement will be. For cost saving purposes, an arrangement of only one single sensor element in a centre area, e. g. in the centre of the cover part or lid of the downdraft device or system, may by favourable. In that case, said only one single sensor element may rest on a centre supporting element, e. g. on a diametrical supporting bar, rather than on the collar. 
     A specific embodiment includes a sensor means, which is electrically connected to a control unit of the downdraft device or system and/or to the control unit of the downdraft cooking hob. 
     At least one respective evaluation unit may be provided on a printed circuit board comprising said control unit. Alternatively, separate electronic circuits on specific printed circuit boards may be provided, which are only communicating, preferably via an MACS bus or the like, to a user interface and/or a power board circuit and/or a control unit circuit or board. 
     The sensor means may be of a type of a capacitance pressure or piezoelectric pressure transducer or of any other type, which is known to being used for weight measurement, in particular usable for small appliances, e. g. small domestic appliances. 
     According to embodiments, the sensor means or module according to anyone of the afore-described essential or specific embodiments is part of or is formed as an add-on module for a household appliance. Said add-on module is adapted to provide for the estimation of the weight of an item placed on a surface of a household appliance, in particular a cookware placed on a top surface of a cooking hob. 
     The add-on module may comprise a touch sensor or a touch control user interface adapted to receive a user input and/or a wireless communication means configured to be connected with a control unit of the household appliance. 
     The object is achieved for a household appliance, which comprises an at least approximately horizontal panel, according to the features of claim  16 . 
     A household appliance according to the invention comprises an at least approximately horizontal panel, in particular a glass panel, which panel is part of or is in functional connection with a scale for weighing an item placed on the panel. The household appliance further comprises or is adapted to be equipped with or coupled with a sensor means or module according to anyone of the above-described essential or specific embodiments. The household appliance may be a cooking hob, in particular an induction cooking hob. 
     In particular, a control and/or processing unit is connected with the sensor means or module for controlling and/or retrieving data from the sensor means or module and/or for processing a signal or data from the sensor means or module. The control and/or processing unit may comprise or be connected to a database and/or with a look-up table and/or cross-reference list, which may also be a part of the database, for receiving at least approximate weight information correlated to the determined displacement or deflection value. 
     According to a specific embodiment, the sensor means or module is arranged in a central zone of the panel. In the case of a cooking hob, the sensor means or module is arranged in a central zone of a top plate of a cooking hob and the cooking hob is adapted to determine the weight of cookware by placing it on said central zone or on one of a number of cooking zones, which are arranged on the top plate. 
     The object is achieved for a method for determining the weight of an item on an at least approximately horizontal panel of a household appliance according to the characterizing part of claim  19 . 
     A method for determining the weight of an item on an at least approximately horizontal panel of a household appliance, in particular on a top plate of a cooking hob, is characterized by an acceleration of a panel section or of a panel reference point or reference area, which acceleration is estimated or determined during a displacement or deflection of the panel section or the panel reference point or reference area due to a placing of the item on the panel. The panel reference point or reference area may be locatable or allocatable to a panel surface. In particular, the estimation or determination of the weight is triggered by the placing of the item on the panel or by a user input. 
     The displacement or deflection or bending of the panel section or the panel reference point or panel reference area is particularly estimated or determined by an integration, preferably by an integration over time, of the acceleration or of the accelerated movement. With said integration the value or intensity of the deflection or bending, particularly after finalization of overshooting and stabilization in the deflected or bent condition, may be exactly calculated. Further, having determined the is value or intensity of deflection or bending, an approximate weight estimation may be performed by means of a database, particularly of a look-up table comprised therein. 
     The estimated or determined weight information may be displayed on a display means, which may be a user interface of the household appliance or of the sensor means or module. As an alternative, the weight information may be processed during an operating process run in the household appliance, in particular during a cooking process on a cooking hob. 
     Novel and inventive features of the present invention are set forth in the appended claims. 
    
    
     
       The present invention will be described in further detail with reference to the drawings, in which 
         FIG.  1    is a schematic top view of an induction cooking hob with four cooking zone, a user interface and an acceleration sensor used for weight determination; 
         FIG.  2    is a schematic cross-sectional view of the induction cooking hob of  FIG.  1    along the line II-II; 
         FIG.  3    is a schematic detail view of detail III indicated in  FIG.  2   , with additional components and wiring; 
         FIG.  4    is the schematic cross-sectional view according to  FIG.  1   , but with a cooking pot placed on a centre zone of a top panel of the induction cooking hob for determination of pot weight; 
         FIG.  5    illustrates a schematic structure of an acceleration sensor applied within the induction cooking hob according to  FIG.  1   ; 
         FIG.  6    is the detail view of  FIG.  3   , however with the acceleration sensor being replaced by a reflective photointerrupter for determination of pot weight according to a second embodiment; 
         FIG.  7    is a detail illustration of the photointerrupter of  FIG.  6   ; 
         FIG.  8   a    illustrates the top panel of the induction cooking hob under the stress of an sample weight exemplifying determination of pot weight according to a third embodiment; 
         FIG.  8   b    illustrates the components of the evaluation circuitry for the weight determination according to the third embodiment; 
         FIG.  9    illustrates schematically a sensor positioning for a fourth embodiment for pot weight determination; and 
         FIG.  10    illustrates the disassembled arrangement of the device of  FIG.  9   . 
     
    
    
     With  FIGS.  1  and  2   , both in a top view and in a cross-sectional view along the line II-II indicated in  FIG.  1   , an induction cooking hob  1  is schematically illustrated, indicating by circles four cooking zones A, B, C, D rectangularly arranged on a glass ceramic top panel  3 . Each cooking zone A, B, C, D is heated by induction coils  5  arranged close to a bottom surface  7  of the top panel  3 . The induction cooking hob  1  is further equipped with a user interface  9  positioned at the front edge of the induction cooking hob  1 . The induction cooking hob  1  further comprises an accelerometer  11 , i. e. an acceleration sensor. Said accelerometer  11  is configured to determine and/or measure an acceleration, which may be a vibration or just an accelerated downwards movement, of the centre of the top panel  3  in vertical direction during or due to the impact of a manual or mechanical action onto the top side  13  of the top panel  3  or of a placement of a load like a cooking pot  15  filled with food. 
     The user interface  9  comprises a touch sensitive display adapted to receive user inputs for the operation of the cooking zones A, B, C, D and to display information, for example status information of the cooking zones A, B, C, D. The user can operate the cooking zones A, B, C, D through touch switches A′, B′, C′, D′, each one thereof assigned to one of the cooking zones A, B, C, D. Further touch switches  17  for other hob functions are covered as well. 
       FIG.  3    illustrates a detail view of one of the cooking zones A, B, C, D together with a schematic presentation of the wiring required for its operation. This illustration can also be seen as a basic configuration generally for an induction cooking hob  1  using the example of only one cooking zone A, B, C, D.  FIG.  3    shows the section with the one cooking zone A, B, C, D, with the top panel  3  supporting a cooking pot  15  above the cooking zone A, B, C, D. The cooking zone A, B, C, D is exposed to electromagnetic waves emanated from the induction coil  5  located underneath the cooking zone A, B, C, D, the waves inducing eddy currents in the bottom of the cooking pot  15  with the effect of heating up said pot bottom. Located in the area of the cooking zone A, B, C, D is a thermal sensor  19 , such as a thermostat, providing information about a temperature in this area. Further, an induction generator  21  for magnetic waves is shown, which is connected to a controller  23 , which controls the signals and the energy of the signals generated by the generator  21 . A user interface controller  25  is also shown, which is connected to the controller  23  and to the accelerometer  11 , which is a micro-electromechanical system (MEMS) in the present example. As illustrated, the micro-electromechanical system  11  is attached to the induction cooking hob  1  indirectly via a dielectric shield  27 , which may be made of a mica mineral substance being a hard substance, which does not substantially dampen vibrations and which protects the micro-electromechanical system  11  from electromagnetic waves emanated from the induction coil  5  or an electric field that builds up or is present during operation or at the induction cooking hob  1 . At the same time, mica also provides good thermal isolation against heat transmitted from e. g. a hot cooking pot  15  through the glass ceramic top panel  3 . 
     The above-described setup is used for the determination of the weight of the cooking pot  15  and specifically the weight of its content, particularly for weighing out newly added ingredients. 
     As illustrated with  FIG.  4   , the placing of the cooking pot  15  causes the top panel  3  of the induction cooking hob  1  to bend or deflect downwardly due to the weight of the cooking pot  15  (excessively shown for reasons of clarity). The magnitude of the bending or deflection is dependent on the weight value, so that the actual weight can be determined by measuring the said bending or deflection magnitude, which is a replicable process. Said bending or deflection measurement is performed by an integration over time of the acceleration or the accelerated movement of the reference area in the centre zone of the top panel  3  by means of the accelerometer  11 , or the MEMS, respectively, which centre zone is also the position of fixation of the accelerometer  11  and is signalized on the top surface  13  of the top panel  3  as being the defined weighing area of the induction cooking hob  1 . 
       FIG.  5    illustrates schematically the structure of the MEMS acceleration sensor  11 , which is of the type of a gravity sensor. Basically, the MEMS structure provides three piled plates  29   a ,  29   b ,  29   c  connected with each other by means of spiral springs  31 . The upper and the lower plates  29   c ,  29   a  are fixed and the intermediate plate  29   b  is movable, but its movability is limited by the spiral springs  31 . Such setup provides a series connection of two capacitors  33  with variable capacities because of a variable distance of the two plates  29   a - 29   b ,  29   b - 29   c  of a capacitor  33  following the movement of the intermediate plate  29   b . In the situation of no movement or a constant movement, the plates  29   a ,  29   b ,  29   c  are in an equidistant arrangement, but in the case of an accelerated movement of the acceleration sensor  11  the intermediate plate  29   b  is moved due to its moment of inertia. The occurring capacity changes are proportional to the acceleration and an integration of actual capacities allows the deduction of the covered deflection. 
     A second embodiment for the determination of the weight of a cooking pot  15  is shown in  FIG.  6   . The structure of this embodiment is similar to the first one, which is readily understood when comparing it with  FIG.  3   . Similar to the practice of the first one, also the weight determination according to the second embodiment relies on the measurement of the magnitude of the displacement or deflection of the top panel  3  of the induction cooking hob  1  under the load of a cooking pot weight. However, said displacement or deflection is determined by means of an optical device comprising a photo sensor or photointerrupter  35 . 
     There are several types of such optical sensors known, usually operating with light emitting  37  and receiving  39  elements. The two basic types of photointerrupters  35  are the transmissive type (gap type) and the reflective type. The transmissive type is easier to operate because all optical elements  37 ,  39  are already adjusted. A signal is generated by interrupting light emitted from the light emitting element  37  on its way to the light receiving element  39  by an obstacle. The reflective type photointerrupter  35  needs a reflecting surface  41  for reflecting light emitted from the light emitting element  37 . Since the light emitting and receiving elements  37 ,  39  facing the same direction, the distance of the reflecting surface  41  to the reflective type photointerrupter  35  is determined by the duration or transit time of emission and receipt of a light signal. 
     In the present example a reflective type photointerrupter  35  is used. An example of this sensor type, which is shown in  FIG.  7   , is adapted to be mounted on a printed circuit board which may be fixed on an internal housing or compartment structure inside of the induction cooking hob  1 , particularly on or at a carrier part for at least one induction coil  5  or on a protection box for the electronic components and circuit boards of the induction cooking hob  1 . Generally, said fixation can be arbitrarily chosen, it just has to be ensured to choose a stationary position, uncoupled from the top panel  3 . The photointerrupter  35  comprises a housing  43 , said light emitting element  37 , said light receiving element  39  and two ports  45  for each of said elements. Via these ports  45 , an electronic unit on the printed circuit board and associated software the above-mentioned duration or transit time between emission and receipt of a light signal can be identified, which light signal is reflected from a reflecting surface  41  on the bottom surface  7  of the top panel  3 , see  FIG.  6   . The primary output of the photointerrupter  35  is an analogue signal, which is interpreted by said software. For a trouble-free measurement of said duration or transit time, an adequate distance between photointerrupter  35  and top panel  3  has to be chosen. Said reflecting surface  41  on the bottom surface  7  of the top panel  3  may be applied by conventional printing on glass ceramic surface or by a drop of colour, particularly white colour. An application of a stencil on the glass surface is proposed for having a distance for thermal reasons.                        
       FIG.  8   a    illustrates a third embodiment for weight determination of a cooking pot  15  by way of top panel displacement or deflection by showing an experimental arrangement. In this figure, the weight load provided by a cooking pot  15  is simulated by a sample weight  47  placed on a glass ceramic top panel  3  as used in an induction cooking hob  1 . The scale integrated in the induction cooking hob  1  comprises a strain gauge  49  attached to the bottom surface  7  of the top panel  3  by means of a glue  51 . Due to this fixed attachment, the strain gauge  49  is following the bottom surface  7  in its extension, or elongation, respectively, which occurs when the top plate  3  is bent or deflected downwards. Said elongation exerted on the strain gauge  49  causes a N resistance change which can be measured with applying a voltage thereon or, as a more reliable method, using an evaluation circuit  53  (see  FIG.  8   b   ) comprising a Wheatstone bridge  55  and an instrumentation amplifier  57 . Said evaluation circuit  53  works as follows: when the strain gauge  49  is put under stress (i.e. deflection causing an elongation), there is a resistance change in the strain gauge  49 , which changes the voltage measurable at the Wheatstone resistance bridge  55 . Said voltage is transferred to the instrumentation amplifier  57  as a voltage input V in , which voltage V in  is amplified by the amplifier  57 , in this respect improving readability and the accuracy of the measurement. Insofar, intensity of resistance change in the strain gauge  49  and voltage output V out  of the instrumentation amplifier  57  is proportional to the magnitude of strain gauge elongation and, hence, the top panel deflection. That way, weight of the cooking pot  15  can be determined with high accuracy. 
     More generally, the Wheatstone bridge  55  is used for converting the strain resistance variation into voltage variation. But is since the voltage output of the Wheatstone bridge  55  is typically too small for analysing said variation, an amplifier  57  for amplifying said voltage output may be necessary. The evaluation process for the selection of a suitable amplifier is dependent on a number of different parameters. In many situations the selection of an instrumentation amplifier  57  is convenient. 
     According to  FIG.  8   a   , the voltage output is transmitted to an evaluation circuit  53 , particularly an electronic assembly within the user interface  9 , which displays the weight of the cooking pot  15 , for example on the user interface display, after conversion by means of a concordance list in a database of the induction cooking hob  1 . 
     Finally, a fourth embodiment for weight determination of a cooking pot  15  using an integrated scale in the induction cooking hob  1  is illustrated with  FIGS.  9  and  10   . In this example, there is no displacement or deflection of the entire top panel  3 , rather, an insert arranged or arrangeable in a cutout area of the top panel  3  is displaced or moved in relation to the top panel  3  under the weight of an item to be weighed. The present example shown in  FIGS.  9  and  10   , discloses a cover part  59  of a downdraft device or system, which is particularly a lid  59  of a downdraft exhaust system  61  implemented in a centre area of the cooking hob  1 . The lid  59  is removable for a disassembly of a filter unit  63 , as illustrated with  FIG.  10    showing the disassembled lid  59  and the cylindrical filter cartridge  63 . 
     As shown in  FIG.  9   , the downdraft exhaust system  61  is arranged in a cutout  65  in the centre area of the cooking hob  1 . Said downdraft exhaust system  61  comprises a cylindrical exhaust compartment  67  including said cylindrical filter cartridge  63 . The upper frame  69 , which is arranged close to the circular cutout  65  in the top panel centre, of the cylindrical exhaust compartment  67  also forms a collar for supporting the lid  59  and provides a support for three weight sensors  71 , which are arranged on the corners of an equilateral triangle. That way, the weight sensors  71  are squeezed between the lid  59  and the upper frame  69  of the exhaust compartment  67 . 
     The weight sensors  71  are preferably fixed to the upper frame  69  of the exhaust compartment  67 , which allows them to be connected to the controller  23  or to the user interface  9  of the cooking hob  1  by wired connection. However, also coupling them to the lid  59  is possible, particularly when they are equipped with wireless communication means for a communication with the controller  23  or user interface  9 . 
     Although an illustrative embodiment of the present invention has been described herein with reference to the accompanying drawing, it is to be understood that the present invention is not limited to that precise embodiment, and that various other changes and modifications may be affected therein by one skilled in the art without departing from the scope or spirit of the invention. All such changes and modifications are intended to be included within the scope of the invention as defined by the appended claims. In particular, the above examples are all described with reference to induction cooking hobs  1 , but the invention is not limited to this type. Rather, all other types of cooking hobs shall be covered as well, for example radiant hobs or gas hobs. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  induction cooking hob 
           3  top panel 
           5  induction coil 
           7  bottom surface 
           9  user interface 
           11  accelerometer 
           13  top side/top surface 
           15  cooking pot 
           17  touch switches 
           19  thermal sensor 
           21  induction generator 
           23  controller 
           25  user interface controller 
           27  dielectric shield 
           29   a ,  29   b ,  29   c  plates 
           31  spiral spring 
           33  capacitor 
           35  photointerrupter 
           37  light emitting element 
           39  light receiving element 
           41  reflecting surface 
           43  housing 
           45  port 
           47  sample weight 
           49  strain gauge 
           51  glue 
           53  evaluation circuit 
           55  Wheatstone bridge 
           57  instrumentation amplifier 
           59  cover part/lid 
           61  downdraft exhaust system 
           63  filter cartridge 
           65  cutout 
           67  exhaust compartment 
           69  upper frame 
           71  weight sensors 
         A, B, C, D cooking zones 
         A′, B′, C′, D′ touch switches 
         V in , V out  input voltage, output voltage