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Original question:

Compiler/EVM430-F6779: Help with THD measurements

EVM430-F6779: Regarding THD(harmonics measurement) implementation using CCS software

Avinash B
Prodigy 140 points
Part Number: EVM430-F6779

Hello,

  So I have  few doubts for THD implementation for EVM430-F6779 board.

  1. In the user guide of  EVM430-F6779 board it is given that, to calculate fundamental RMS voltage, a pure sine wave is generated. So my doubt in this case is how the pure sine wave needs to be generated, is it using analog signal generator or by defining sine function.
  2. In the same document it is given for THD implementation that, for calculating THD proper macro must be defined in metrology-template.h file but this was the case when we would had used IAR software but I am currently using EMDC software generated source files in CCS software. So how can we implement THD in CCS?

Thanks 

Avinash

  • 0
    TI__Guru 56685 points

    Hello,

    1. See section 3.2.3.1.2 Pure Waveform Samples of the User Guide for this TI Design. It explains that the sine wave is generated by the SW, so its not measured, but values are calculated and used as reference.
    2. THD implementation is not supported by EMDC software and is only supported in the older IAR Based SW solution. 
  • 0 in reply to Jace H
    Prodigy 140 points

    Hello Sir,

    Thankyou for your response.

    So I went through the following document and saw the following section and understood that a pure sine wave needs to generated through software implementation and also the following THD implementation is available on IAR and not in EMDC generated source code.

    So as per the given instructions in following photo, I am implementing a pure sine wave using a sin( ) function in math.h library.

    So my current sine function parameters are as follows: 

    sine function : A*sin(2*3.14*(F/Fs)*n) where Fs is sampling frequency and F is frequency and A is amplitude.

    So according to these how to set the parameters for pure sine wave generation for THD measurement.

    My EMDC configurations are as follows:

    If there is another method to generate pure sine wave generation then it would be helpful.

    Thanks.

    Avinash

  • +1 in reply to Avinash B
    TI__Guru 56685 points

    Hello Avinash,

    The paragraph you highlighted is telling you what the parameters need to be set to. You have to set it to the ideal waveform you want to measure.

    Amplitude == full scale range (of ADC)

    Frequency == measured frequency of voltage capture

    Phase == iteratively adjusted to lock onto measured voltage waveform. 

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