Fill-level measurement device

A method for checking a functionality of a fill-level measurement device, the method comprising:

• providing the fill-level measurement device, including:
• a transmission unit via which high-frequency signals can be sent to the filling material and, after reflection on the filling material surface, can be received as received signals, wherein the transmission unit is embodied as an electrically conductive measuring probe which, in the installed state of the fill-level measurement device, extends perpendicularly to the container base;
• a high-frequency unit, including:
• two activatable, high-frequency sources, each of which is designed for generating the high-frequency signal, wherein one of the two high-frequency sources is designed in an inverting manner;
• and
• two activatable receivers via which the received signal can be time-prolonged in each case, wherein one of the two receivers is designed in an inverting manner;
• a control unit embodied to activate one of the high-frequency sources such that the activated high-frequency source generates the high-frequency signal, and to activate one of the receivers such that the activated receiver converts the received signal into a time-prolonged evaluation signal;
• an evaluation unit embodied to determine a defined property of the evaluation signal, including a polarity, an edge steepness, a signal amplitude, and/or a signal transit time of at least one signal maximum, and to determine the fill-level on the basis of the signal transit time of the at least one signal maximum;
• and
• a diagnosis unit embodied to:
• control the control unit to deactivate the high-frequency source that is active and/or the receiver that is active and to activate the high-frequency source that was previously inactive and/or the receiver that was previously inactive, so that the polarity of the received signal or of the evaluation signal is inverted;
• control the evaluation unit such that the defined property of the evaluation signal is determined before and after the switching;
• and classify the high-frequency unit as non-functional if the defined property of the evaluation signal changes at least by a defined value as a result of the switching,
• wherein the evaluation unit is further embodied to:
• invert the polarity of the evaluation signal if the polarity changes as a result of the switching;
• and determine the defined property on the basis of the polarity-inverted evaluation signal, and
• wherein the diagnosis unit is further embodied to control the evaluation unit such that, in each case before and after the switching of the active high-frequency source or of the active receiver, its polarity is determined as the defined property of the evaluation signal and to classify the high-frequency unit as non-functional if the polarity of the evaluation signal does not change as a result of the switching;
• generating the high-frequency signal via the high-frequency source that is switched to be active;
• sending the high-frequency signal to the filling material and receiving the corresponding received signal after reflection an the filling material surface;
• receiving the received signal via the receiver that is switched to be active such that a time-prolonged evaluation signal is generated;
• determining at least one signal maximum of the evaluation signal;
• determining at least one defined property of the at least one signal maximum;
• switching the high-frequency source that is active so as to be passive, and vice versa, and/or switching the receiver that is active so as to be passive, and vice versa, and subsequently repeating the prior method steps;
• comparing the defined property before and after the switching;
• and
• classifying the high-frequency unit as non-functional when the defined property of the evaluation signal has changed at least by a defined value as a result of the switching.