Device for determining at least one measured variable - in particular the pH value - having at least one sensor unit and at least one transmitter, wherein the sensor unit is designed to generate at least one electrical primary signal in dependence on the measured variable, wherein the sensor unit is designed to transmit the primary signal to the transmitter via an analog output interface and wherein the transmitter is designed to process the primary signal, and wherein the sensor unit has a housing, wherein the sensor unit has only the analog output interface, wherein the sensor unit is free of elements which generate a digital signal from the primary signal and/or determine a value of the measured variable from the primary signal, and that the sensor unit is therefore not able to determine the value of the measured variable from the primary signal or to digitize the primary signal for further communication and wherein the sensor unit has at least one data carrier, wherein data associated with the sensor unit can be stored in the data carrier, and wherein the data carrier is arranged on and/or in the housing of the sensor unit, and wherein the device comprises an electronic insert, wherein the sensor unit is assigned to the at least one electronic insert, wherein the electronic insert has at least one analog input interface, wherein the electronic insert is designed to process at least the primary signal with respect to the measured variable, and wherein the electronic insert and the transmitter are reversibly connected to one another, and wherein the transmitter for processing primary signals of at least one sensor unit has at least one electronics receptacle for an electronic insert assigned to the sensor unit and processing the primary signals of the sensor unit, wherein the electronics receptacle allows reversible insertion of the electronic insert. wherein the sensor unit has only the analog output interface, wherein the sensor unit is free of elements which generate a digital signal from the primary signal and/or determine a value of the measured variable from the primary signal, and that the sensor unit is therefore not able to determine the value of the measured variable from the primary signal or to digitize the primary signal for further communication and wherein the sensor unit has at least one data carrier, wherein data associated with the sensor unit can be stored in the data carrier, and wherein the data carrier is arranged on and/or in the housing of the sensor unit, and wherein the device comprises an electronic insert, wherein the sensor unit is assigned to the at least one electronic insert, wherein the electronic insert has at least one analog input interface, wherein the electronic insert is designed to process at least the primary signal with respect to the measured variable, and wherein the electronic insert and the transmitter are reversibly connected to one another, and wherein the transmitter for processing primary signals of at least one sensor unit has at least one electronics receptacle for an electronic insert assigned to the sensor unit and processing the primary signals of the sensor unit, wherein the electronics receptacle allows reversible insertion of the electronic insert.