Patent ID: 7730760

Claim:
A method for checking the proper functioning of a fill-level measuring device which determines the fill level of a fill substance in a container, the fill substance defining a substance, comprising the steps of: transmitting measuring signals toward the surface of the substance at which the measuring signals are reflected; performing a distance determination, at predetermined or selectable time intervals based on the travel time of the measuring signals; ascertaining a current wanted echo signal at a current fill level based on the current measured value curve; ascertaining an expected value for quality of a wanted echo signal at least one predetermined fill level; ascertaining a signal/noise ratio of a wanted echo signal to disturbance echo signals as the expected value for quality; predetermining a critical value of a minimum signal/noise ratio for the proper functioning of the fill-level measuring device; comparing the ascertained expected value for quality of the wanted echo signal at the predetermined fill level with a predetermined critical value for quality; and diagnosing an error condition, when the ascertained expected value falls below the predetermined critical value.