Abstract: The present invention relates to a device and related method that includes an ultrasonic transducer, an acoustic waveguide acoustically coupled to the ultrasonic transducer and transmitting and receiving electronics for transmitting and receiving ultrasound waves via the ultrasonic transducer in an explosion-protected housing. The transmitting and receiving electronics has an energy storage connected to an amplifier circuit, wherein control signals for the ultrasonic transducer transmitted from outside can be amplified to such an extent that ultrasonic signals significantly strong for monitoring can be generated. By means of the acoustic waveguide, the ultrasonic signals are guided outside through an explosion-protected passthrough in the housing and are coupled into the object. As a result, objects can be continuously monitored in explosion-protected zones without violating the safety regulations and without a stoppage of the associated system or draining of the objects.