Calibration of microcomputer-based metering apparatus

In combination:

• a microcomputer based electric metering device for monitoring electrical parameters in an electric power distribution system, said device comprising:
• input means for sensing said electrical parameters to generate sensed parameter values;
• processor means for applying an associated adjustable scaling factor to each sensed parameter value to generate scaled parameter values;
• display means displaying said scaled parameter values and said associated adjustable scaling factors;
• and
• user interface means for selecting a selected electrical parameter value and for adjusting the associated adjustable scaling factor to generate an adjusted scaling factor, said processor means including means applying said adjusted scaling factor to said sensed parameter value generated from said selected electrical parameter to generate an adjusted scaled parameter value and displaying on said display means said adjusted scaled parameter value in association with the associated adjusted scaling factor;
• and
• a source of stable values of said selected electrical parameter connected to said input means;
• and
• a reference meter to which said stable values of said selected electrical parameter are also applied for generating reference parameter values of said selected electrical parameter, said adjustable scaling being adjusted through said user interface means for making said adjusted scaled parameter values substantially equal to said reference parameter values.

A method of calibrating a microcomputer based metering device which applies an adjustable scaling factor to an input electrical parameter to generate a metered parameter value of the input electrical parameter and having a display means for displaying the metered parameter value, said method comprising the steps of:

• connecting an electrical source generating a stable value of said input electrical parameter to said metering device;
• displaying said adjustable scaling factor on said display means in association with said metered parameter value;
• measuring said input electrical parameter with a precision meter to generate a reference parameter value for said input electrical parameter;
• and
• adjusting said adjustable scaling factor by reference to said display means until said metered parameter values substantially equals said reference parameter value.