Patent ID: 8581159

Claim:
A method for controlling a cooktop having a cooktop panel, the method comprising: providing the cooktop with at least one cooking zone that is heatable by an induction heating device disposed below the cooktop panel when the cooktop is in an installed position; providing an electrical control system including a processing unit and a memory; providing first, second and third heat sensor units beneath the cooktop panel in a region of a measuring spot, the first heat sensor unit being configured to measure heat flow emanating downward from substantially only the cooktop panel in an area of the at least one cooking zone, the second and third heat sensor units being configured to measure heat flow emanating downward in an area of the cooking zone from the cooktop panel and a cooking utensil disposed on the cooktop panel; performing a reflection measurement to determine an emissivity ε cooking utensil of a bottom of the cooking utensil using at least one emissivity heat sensor and a light source; heating the cooking utensil using the induction heating device during a heat-up phase; heating the cooktop panel in an area of the cooking zone to a predetermined desired temperature T cooking utensil during the heat-up phase; storing a value for the emissivity ε cooking utensil of the bottom of the cooking utensil in the memory of the electrical control system; heating the region of the measuring spot using an auxiliary heater to a temperature T desired , T desired being at least approximately equal to the predetermined desired temperature T cooking utensil ; upon reaching T desired at the measuring spot and T cooking utensil at the cooking zone, calculating, in a cooking phase following the heat-up phase, a ratio from output signals of the second and third heat sensor units using the electrical control system; determining an actual temperature of the bottom of the cooking utensil from the ratio by using a temperature of a lower surface of the cooktop panel T cooktop panel measured by the first sensor unit and the value of the emissivity ε cooking utensil of the bottom of the cooking utensil; and controlling the induction heating device as a function of the actual temperature of the bottom of the cooking utensil.