Developments in power system measurements starting from the conventional analogue, through digital to microprocessor based measurements are reviewed. Then is presented a microprocessor- based power system monitor (μPSM) that scans the three phase voltages and currents and computes therefrom RMS voltages and currents, average active, reactive and complex power, as well as power factor and maximum demand. Our μPSM is thus meant to replace the conventional analogue meters and recorders on control panels used in generating, receiving and sub stations, load despatch centres, control rooms of bulk power consumers, etc. μPSM can also find application in power system data loggers, alarms and annunciators, power system relaying, load frequency control, etc, as the basic data acquisition unit.