SLAA517F May   2012  – August 2021 MSP430F6720A , MSP430F6720A , MSP430F6721A , MSP430F6721A , MSP430F6723A , MSP430F6723A , MSP430F6724A , MSP430F6724A , MSP430F6725A , MSP430F6725A , MSP430F6726A , MSP430F6726A , MSP430F6730A , MSP430F6730A , MSP430F6731A , MSP430F6731A , MSP430F6733A , MSP430F6733A , MSP430F6734A , MSP430F6734A , MSP430F6735A , MSP430F6735A , MSP430F6736 , MSP430F6736 , MSP430F6736A , MSP430F6736A

 

  1.   Trademarks
  2. 1Introduction
  3. 2System Diagrams
  4. 3Hardware Implementation
    1. 3.1 Power Supply
      1. 3.1.1 Resistor Capacitor (RC) Power Supply
    2. 3.2 Analog Inputs
      1. 3.2.1 Voltage Inputs
      2. 3.2.2 Current Inputs
  5. 4Software Implementation
    1. 4.1 Peripherals Setup
      1. 4.1.1 SD24 Setup
    2. 4.2 Foreground Process
      1. 4.2.1 Formulas
        1. 4.2.1.1 Voltage and Current
        2. 4.2.1.2 Power and Energy
    3. 4.3 Background Process
      1. 4.3.1 Voltage and Current Signals
      2. 4.3.2 Phase Compensation
      3. 4.3.3 Frequency Measurement and Cycle Tracking
      4. 4.3.4 LED Pulse Generation
  6. 5Energy Meter Demo
    1. 5.1 EVM Overview
      1. 5.1.1 Connections to the Test Setup for AC Voltages
      2. 5.1.2 Power Supply Options and Jumper Settings
    2. 5.2 Loading the Example Code
      1. 5.2.1 Opening the Project
  7. 6Results and Calibration
    1. 6.1 Viewing Results
    2. 6.2 Calibrating the Meter
      1. 6.2.1 Gain Correction
      2. 6.2.2 Phase Correction
      3. 6.2.3 Metrology Results
  8. 7References
  9. 8Schematics
  10. 9Revision History

4.3 Background Process

The background process uses the ΣΔ interrupt as a trigger to collect voltage and current samples (three values in total). These samples are further processed and accumulated in dedicated 48-bit registers. The background function deals mainly with timing critical events in software. Once sufficient samples (1 second worth) have been accumulated then the foreground function is triggered to calculate the final values of VRMS, IRMS, power and energy. The background process is also wholly responsible for energy proportional pulses, frequency and power factor calculation for each phase. Figure 4-2 shows the flow diagram of the background process.

GUID-5DA86087-CB63-4B35-B2D4-7797E7FCD8FA-low.gifFigure 4-2 Background Process

The following sections discuss the various elements of electricity measurement in the background process.