SLAA494B May   2011  – September 2023 MSP430AFE221 , MSP430AFE222 , MSP430AFE223 , MSP430AFE231 , MSP430AFE232 , MSP430AFE233 , MSP430AFE251 , MSP430AFE252 , MSP430AFE253

 

  1.   1
  2.   Implementation of a Single-Phase Electronic Watt-Hour Meter Using the MSP430AFE2xx
  3. 1 Trademarks
  4. 2 Introduction
  5. 3 Block Diagram
  6. 4 Hardware Implementation
    1. 4.1 Power Supply
      1. 4.1.1 Resistor Capacitor (RC) Power Supply
      2. 4.1.2 Switching-Based Power Supply
    2. 4.2 Analog Inputs
      1. 4.2.1 Voltage Inputs
      2. 4.2.2 Current Inputs
  7. 5 Software Implementation
    1. 5.1 Peripherals Setup
      1. 5.1.1 SD24 Setup
    2. 5.2 Foreground Process
      1. 5.2.1 Formulas
        1. 5.2.1.1 Voltage and Current
        2. 5.2.1.2 Power and Energy
    3. 5.3 The Background Process
      1. 5.3.1 Voltage and Current Signals
      2. 5.3.2 Phase Compensation
      3. 5.3.3 Frequency Measurement and Cycle Tracking
      4. 5.3.4 LED Pulse Generation
    4. 5.4 Energy Meter Configuration
  8. 6 Energy Meter Demo
    1. 6.1 EVM Overview
      1. 6.1.1 Connections to the Test Setup or AC Voltages
      2. 6.1.2 Power Supply Options
    2. 6.2 Loading the Example Code
      1. 6.2.1 Opening the Project
  9. 7 Results
    1. 7.1 Viewing Results on PC
    2. 7.2 Viewing Results During Debug
  10. 8 Important Notes
  11. 9 Schematics
  12. 10References
  13. 11Revision History

4.2 Analog Inputs

The MSP430 analog front end that consists of the SD24 ADC is differential and requires that the input voltages at the pins do not exceed ±500 mV (gain = 1). To meet this specification, the current and voltage inputs must be divided down. In addition, the SD24 allows a maximum negative voltage of -1 V; therefore, the ac signals from the mains can be directly interfaced without the need for level shifters. The following sections describe the analog front end used for voltage and current channels.