Fill-level measuring device

A method for determining the serviceability of a field device that comprises at least one electronic unit for measuring a process variable, and the at least one electronic unit is supplied by means of an energy store of the field device, the method comprising:

• measuring a capacitance of the energy store;
• measuring a power consumption at the energy store;
• and
• classifying the field device as unserviceable when the capacitance of the energy store falls below a defined minimum capacitance or/and when the power consumption deviates from a predefined normal consumption.

A fill-level measuring device, comprising:

• an energy store;
• a signal-generating unit which is fed by the energy store and is designed to emit a radar or ultrasound signal in a direction of a filling material in a container;
• an evaluation unit which is fed by the energy store and is designed to determine a fill level on the basis of a signal reflected at a filling material surface;
• and
• a control unit designed to:
• switch on and off the signal-generating unit and/or the evaluation unit or individual function blocks thereof;
• determine a power consumption at the energy store;
• determine a capacitance of the energy store;
• and
• classify the field device as unserviceable when the capacitance of the energy store falls below a minimum capacitance or when the power consumption deviates from a defined normal consumption.