Abstract: A method for ascertaining an internal resistance of a sensor element. The method includes: ascertaining a reference voltage between a first electrode and a second electrode; impressing of a first current pulse having a first current by a pulse-generating unit at a first time; ascertaining at least two voltage values at two different times after an elapsing of a first settling time after the first time; ending the first current pulse and impressing an opposite second current pulse having a second current at a second time, ending the second current pulse at a third time; ascertaining a linear equation as a function of the at least two voltage values and the times; extrapolating a voltage value at the first time using the linear equation; ascertaining an internal resistance of the sensor element as a function of the extrapolated voltage value, the reference voltage, and the first current.