The subject matter relates to a circuit arrangement for monitoring the function of a fill level measuring apparatus, and particularly of a vibration level switch, including a first piezo-electric vibration device as a transmitting device, a second piezo-electric vibration device as a receiving device, an oscillator circuit, the input and output of which during normal operation are connected to the vibration devices, the second connections of which devices are at common ground potential, and a monitoring circuit for monitoring the function. The monitoring circuit has a switch element for temporarily connecting the first and second vibration devices in parallel to each other and for connecting the vibration devices, which are connected in parallel to each other, in series to a capacitance measuring apparatus during a temporary monitoring mode according to a first embodiment, a capacitance value (c) being supplied by the monitoring circuit as an indicator of the function of the vibration devices and/or of lines to the vibration devices.