An add-on module for a sensor, such as a fill and/or limit level sensor, comprising a coupling unit, which is arranged to be communicatively couplable to at least one predetermined sensor, and a control unit, which is configured to enable and/or disable data processing of the at least one predetermined sensor. Furthermore, the invention also relates to a sensor unit for detecting a fill level and/or limit level, comprising at least one sensor, and such an additional module, as well as a method for controlling such a sensor unit.