A synchronized two-phase sinewave generator for AC metrology systems compensations

A slave audio two-phase sinewave generator, which output can be directly synchronized to a master generator, is here described, to be used in ac metrology setups to provide additional “compensations” signals (traditionally derived with expensive multi-decadic inductive voltage dividers). The generator is based on two direct-digital-synthesis (DDS) chips, programmed via parallel printer PC interface, their clock provided by a phase-locked loop circuit which ensure frequency and phase synchronization of DDS outputs to the master generator. Synchronization reference signal can be provided with an optical link reference channel, which avoids interference and ground loops. In its present implementation, output is 10 Vpk, frequency range 500 Hz to 4 kHz; total harmonics distortion is contained to -65 dB, amplitude stability is better than 500 ppm over 24 h