Microprocessor Determination of Phase Angle in the Presence of Harmonics

An instrument based on the look-up table technique in a microprocessor is developed to measure the phase angle between the fundamental components of two nonsinusoidal periodic signals. In real-time mode, the phase angle is measured with a resolution of 1°, while a resolution of 0.10° is achieved in the steady-state mode. Additional hardware is also incorporated to ensure that frequency variation in the range 45-55 Hz does not introduce any additional error in measurement.