TIDUFB8 December   2024

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
    2. 1.2 End Equipment
    3. 1.3 Electricity Meter
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Voltage Measurement – Analog Front End
      2. 2.2.2 Current Measurement Analog Front End
      3. 2.2.3 Input Voltage
      4. 2.2.4 Clock
    3. 2.3 Highlighted Products
      1. 2.3.1 AMC130M02
      2. 2.3.2 MSPM0G1106
      3. 2.3.3 LMK6C
      4. 2.3.4 TLV76133
  9. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Software Requirements
      1. 3.2.1 Formulas
      2. 3.2.2 Metrology Software Process
        1. 3.2.2.1 UART for PC GUI Communication
        2. 3.2.2.2 Direct Memory Access (DMA)
        3. 3.2.2.3 ADC Setup
        4. 3.2.2.4 Foreground Process
        5. 3.2.2.5 Background Process
        6. 3.2.2.6 Software Function per_sample_dsp ()
        7. 3.2.2.7 Frequency Measurement and Cycle Tracking
        8. 3.2.2.8 LED Pulse Generation
    3. 3.3 Test Setup
      1. 3.3.1 Power Supply and Jumper Settings
      2. 3.3.2 Viewing Metrology Readings and Calibration
      3. 3.3.3 Calibration
        1. 3.3.3.1 Voltage and Current Offset Calibration
        2. 3.3.3.2 Voltage and Current Gain Calibration
        3. 3.3.3.3 Active Power Gain Calibration
        4. 3.3.3.4 Offset Calibration
        5. 3.3.3.5 Phase Calibration
    4. 3.4 Test Results
      1. 3.4.1 Electricity Meter Metrology Accuracy Results
  10. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
      3. 4.1.3 PCB Layout Recommendations
        1. 4.1.3.1 Layout Prints
      4. 4.1.4 Altium Project
      5. 4.1.5 Gerber Files
      6. 4.1.6 Assembly Drawings
    2. 4.2 Tools and Software
    3. 4.3 Documentation Support
    4. 4.4 Support Resources
    5. 4.5 Trademarks
  11. 5About the Author

3.3.3.4 Offset Calibration

After performing gain calibration, if the accuracy at low currents is not acceptable, offset calibration can be done. Offset calibration removes any crosstalk, such as the crosstalk to the current channels of a phase from the line voltages.

To perform active power offset calibration for a phase, add the offset to be subtracted from the active power reading (in units of mW) to the current value of the active power offset (labeled Voltage AC offset in the meter calibration factors window) and then enter this new value in the Voltage AC offset field in the Manual Calibration window. As an example, if the Voltage AC offset has a value of 200 (0.2W) in the meter calibration window, and subtracting an additional 0.300mW is desired, then enter a value of 500 in the Voltage AC offset field in the Manual Calibration window. After entering the value in the Voltage AC offset field in the Manual Calibration window, press the Update meter button.

To perform reactive power offset calibration for a phase, a similar process is followed as the process used to perform active power offset calibration.