The invention proposes a sensor device having a sensor, particularly an ultrasound sensor, comprising means for generating and detecting waves, particularly sound waves, wherein the means for detecting transform received waves into electric signals and the electric signals can be evaluated by an evaluation unit. According to the invention, a function monitoring device is provided, which is designed to determine an impedance characteristic curve of the sensor as a function of an excitation frequency. The invention further relates to a method for operating the sensor device.