Basically, all these meters will be allocated a factor value upon calibrating. This value will be written to EEPROM via a hand-held device using IR. Upon startup, the factor value is read from non-volatile mem, being the EEPROM, and inserted into the interrupt generated by the external source.. the external source, the measurement chip, which is an Analog Device measurement chip, clocks out pulses in accordance with power being used. The factor is to account for the .. lets say 0.1% variance due to coefficients.. for the meter must be a 1% meter according to IECC specs.. it seems to work relatively better than the ADC solution being used previously.