Motor vehicle having occlusion detection for ultrasonic sensors

A distance-measuring apparatus for a motor vehicle, comprising:

• at least one ultrasonic sensor;
• and
• a controller including a processor configured to perform the following:
• apply, by a transmitter unit, an excitation pulse to a diaphragm of the first ultrasonic sensor;
• detect, by an evaluation unit, a measuring signal of the first ultrasonic sensor, and ascertain from the measuring signal a decay time of a natural oscillation of the diaphragm, brought about by the excitation pulse;
• ascertain, from one of the measuring signal of the first ultrasonic sensor or a measuring signal of a second ultrasonic sensor, an echo of the excitation pulse, produced by an object located in a sensing range of the first ultrasonic sensor, and determine at least a first distance value of the object on the basis of the echo;
• and
• signal, by the evaluation unit, an existence of the occlusion at least if (i) the decay time is less than a predetermined threshold value, and (ii) the first distance value is less than a predetermined maximum value, wherein the predetermined threshold value represents a value which is exceeded in the event at least one of ice and dirt is adhered directly to the diaphragm.