A device for measurement of power angle and rotor speed of a synchronous generator has bi-en designed and realized. The device is supplying a signal proportional to the phase angle between the terminal voltage and generated e.m.f. phases of the synchronous machine. A second signal proportional to the rotor speed is also generated. These output signals can be used for both measurement and control purposes. The device under consideration can also be used in conjunction with digital systems through an analog to digital converter (A/D) to perform on-line computation and control. The design and realization of the device depend on high speed digital and linear integrated circuits. The time delays introduced by the device components are negligible compared to the machine time constant , therefore the device is most suitable for applications in both transient and dynamic conditions in synchronous machines. The device is capable of monitoring the variations in the power angle and the rotor speed for both measuring and control purposes. Further, this device can be used as a part of a digital control system to provide stabilizing signals to digital automatic voltage regulator of synchronous machines. The test and calibration results obtained show the capability of the device to monitor the power angle and rotor speed in both steady state and transient conditions.