Accurate measurement of power, energy, and true RMS voltage using synchronous counting

A synchronous measurement method that can be applied for the accurate determination of periodic signals is presented. The method relies on adaptation of the measurement time to the period of the measurement signal. It is based on dual-slope integration performed according to the synchronization signal (input signal). The first phase of integration is fully synchronized with the input signal. The time of the first phase is also measured. The output voltage of the integrator depends directly on the input signal and the time of the first integration phase. Measurement values are the results of arithmetic operations between the time of the second phase of integration and the measuring time (first phase). With this method, an accuracy of 0.1% can be achieved