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

An apparatus for measuring and displaying an electrical parameter of an electrical system, said electrical parameter having a nominal value, said apparatus comprising:

• a non-volatile memory storing a scaling factor;
• a divider providing a first analog voltage from said electrical parameter of said electrical system, said first analog voltage having a first magnitude;
• an analog to digital converter circuit converting said first analog voltage to a first digital value;
• a processor comprising:
• a first routine calculating said scaling factor by subtracting a second digital value from a third digital value, said third digital value representing said nominal value, said second digital value being converted by said analog to digital converter circuit from a second analog voltage from said divider, said second analog voltage having a second magnitude, said divider receiving a third analog voltage having a third magnitude, which represents said nominal value, said second magnitude being less than said third magnitude, said second digital value being less than said third digital value,
• an input circuit for said first routine, and
• a second routine retrieving said scaling factor from said non-volatile memory and adding said scaling factor to said first digital value to provide a sum;
• and
• a display displaying said sum.