The load angle of the synchronous machine is the displacement of the stator magnetic field relative to the rotor (excitation). The static magnetic field is represented by the static voltage and the rotor with angle of the rotor. Through this final work, the process of developing an electronic circuit for measuring the load angle of the the synchronous machine is shown. The synchronous machine load angle measurement device is based on a microcontroller that measures the time between the rotor position signal obtained by a photo sensors detecting a marker on the rotor and passing the armature voltage through the zero. That time is proportional to the load angle. The correct load angle is obtained after the device is idle. The appliance is intended for industrial applications. It must be robust, suitable for mounting on a DIN rail and should provide an analog output signal. Desired signals are required as well as the required electronic circuits for signal processing, control and parameterization of the device. The printed circuit board was made and the code for the microcontroller was written. After fabrication, the measuring device was tested in a laboratory on a synchronous generator connected to the electrical network. The load angle is measured at constant excitation at different generator power values ​​and the functionality of the measuring device is demonstrated.