Hob having a temperature sensor

1. A hob, comprising:

at least one heating zone;

a temperature sensor for detecting a temperature of a cookware element placed on the heating zone; and

a control unit for operating the heating zone, said control unit being constructed to heat up the cookware element during a heating-up phase in at least one operating mode and to regulate the temperature of the cookware element to a target temperature during a holding phase, said control detecting a boiling point of liquid in the cookware element during the heating-up phase based upon the temperature of the cookware element and determining the target temperature as a function of the temperature of the cookware element when the boiling point is detected.

2. The hob of claim 1 , wherein the heating-up phase lasts until a changeover instant after the boiling point has been reached.

3. The hob of claim 1 , wherein the target temperature is a predefined temperature difference lower than the temperature of the cookware element when the control detects the boiling point.

4. The hob of claim 3 , wherein the temperature difference is between 2° C. and 7° C.

5. The hob of claim 1 , wherein the control unit records a temperature curve of the cookware element during the heating-up phase, detects a substantially constant section along the temperature curve, and calculates an average of the temperature within the constant section.

6. The hob of claim 5 , wherein the control unit calculates a gradient of the temperature curve for detecting the constant section.

7. The hob of claim 1 , wherein the control unit deactivates the operating mode and produces a warning signal when the temperature registered by the temperature sensor exceeds a maximum value.

8. A method for operating a hob, comprising:

detecting a temperature of a cookware element placed on a heating zone and heated up during a heating-up phase in at least one operating mode;

detecting a boiling point of liquid contained in the cookware element during the heating-up phase of the cookware element;

regulating the temperature of the cookware element to a target temperature during a holding phase; and

determining the target temperature as a function of the temperature of the cookware element when the boiling point is detected.

9. A cooktop comprising:

a heating zone;

a temperature sensor that detects a temperature;

a controller that receives a temperature signal from the temperature sensor, that determines when a boiling point of a liquid is reached based upon the received temperature signal, and that calculates a target temperature based upon the temperature signal when the controller determines that the liquid has reached a boiling point.

10. The cooktop of claim 9 , wherein the temperature sensor detects a temperature of the liquid.

11. The cooktop of claim 9 , wherein the temperature sensor detects a temperature of a cookware element in the heating zone and containing the liquid.

12. The cooktop of claim 9 , wherein the controller determines that the boiling point is reached when the temperature signal becomes substantially constant.

13. The cooktop of claim 9 , wherein the controller determines that the boiling point is reached when a slope of a curve of the temperature signal over time becomes substantially zero.

14. The cooktop of claim 9 , wherein the controller calculates a target temperature by subtracting between 2 and 7 degrees Celsius from the temperature when the controller determines that the boiling point of the liquid has been reached.

15. The cooktop of claim 9 , wherein the controller further calculates an average temperature over a period of time after the boiling point is reached and calculates the target temperature based upon the calculated average temperature.

16. The cooktop of claim 9 , wherein the controller further operates the heating zone during a heating phase in an operating mode to raise the temperature and operates the heating zone during a holding phase of the operating mode to maintain the temperature near the target temperature.