Method for operating a probe for determining the gas content

The method involves heating a sensor to an operating temperature by an impulse-like operating heater, and counting heater switching impulses that exhibit preset characteristic i.e. length. Aging of the sensor is calculated based on the number of switching impulses, and a threshold value of the switching impulses corresponds to a null value of a heating voltage and/or heating current. The switching impulses are detected depending on heating power or heating current intensity, and the switching impulses are counted when a determined threshold value of the current intensity is exceeded. Independent claims are also included for the following: (1) a computer program for executing a method for operating a sensor (2) a computer program product comprising a program code for executing a method for operating a sensor.