The invention relates to a measuring transducer for process instrumentation, comprising a sensor for sensing a physical or chemical variable. The sensor has at least one electrical element which is embedded in a substrate made of semiconducting material and is electrically separated therefrom by means of a blocked PN junction (DS) during normal operation. In order to monitor the condition of the sensor (3), the PN junction (DS) is connected in the conducting direction in a test mode, and the electrical property of the PN junction, in particular the forward voltage, is determined and is used for monitoring the condition. In addition, a temperature sensor (TS) mounted on the sensor (3) can be monitored by determining, on the basis of the dependence of the forward voltage on the temperature,a comparative value for the temperature sensed by the temperature sensor (TS). If major differences occur, it can be concluded that there is a failure of the sensor (3), and a corresponding error message can be output via a field bus (2).