Correction method for a single chip power meter

The single chip power meter is a programmable mixed signal IC for three phase power line measurement. The DSP block includes two programmable 32 bit processors which executes metering functions and calibration algorithm for six AD converter inputs. In the calibration algorithm correction methods for two major errors have been attempted: for a non-linearity error of input transformers and AD converters, for a phase leading error of the current transformers against the voltage transformers. 30 correction coefficients including frequency dependency are computed by an automatic calibration system. The experimental results demonstrate the efficiency of the corrections: the non-linearity of RMS current measurement has been reduced from ±0.17%FS to ±0.07%FS by the nonlinearity correction, the measurement offset error of three phase power has been reduced from ±3%FS to ±0.25%FS by the phase error correction. These correction techniques bring a breakthrough for cutting the production cost, by permitting use with inexpensive transformers which have less linearity and large characteristic deviation