Method and apparatus employing a scaling factor for measuring and displaying an electrical parameter of an electrical system

摘要

A meter includes an EEPROM storing a scaling factor; a divider providing a first analog voltage from an electrical system; an analog to digital converter (ADC) converting the first analog voltage to a first digital value; and a processor. The processor includes a first routine calculating the scaling factor; an input circuit for the first routine, and a second routine retrieving the scaling factor from the EEPROM and adding the scaling factor to the first digital value to provide a sum for a display. The first routine calculates the scaling factor by subtracting a second digital value from a larger third digital value, which represents a nominal voltage value. The second digital value is converted by the ADC from a second analog voltage from the divider, that receives a larger third analog voltage representing the nominal voltage value.