Abstract: An apparatus for determining and/or monitoring a physical or chemical process variable of a medium, having a sensor unit, which produces a measurement signal with a piece of process variable-dependent, basic information, and having an evaluation unit which, from the measurement signal of the sensor unit, determines a measured value for the process variable, and which produces an output signal with information concerning whether the measured value is greater or smaller than a limit value. A first and second modulation range are provided, and the evaluation unit modulates the output signal within the first or second modulation range with the basic information of the measurement signal, with the evaluation unit modulating the output signal within the first modulation range when the process variable is smaller than the limit value, and with the evaluation unit modulating the output signal within the second modulation range when the process variable is greater than the limit value.