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MSP430F67791: How to understand about the raw ADC values from the Energy Measurement Design Center (EMDC) library?

Part Number: MSP430F67791

Tool/software:

To give some context to my project:

  • I'm using the EMDC library GUI to generate a code to read Current Transformer (CT) Irms.. I do not have the Development Kits mentioned in the user guide. I only have my custom PCB with MSP430F67791 and the programmer to flash code onto it. 

  • The library consists of the kit EVM430-F6736 which has an HMI display (which I presume is to display the readings). Now since I do not have the kit, I have to read the raw Irms ADC values from the code.


The raw IRMS value I think always comes half of what I'm seeing with my Multimeter. For e.g. (check attached screenshot), the multimeter reading is 9.2A and raw is 4795. This value is responsive, I mean it goes to near-zero when I turn off the load, and it rises with load.

Now I want to get a better understanding of this Raw ADC value to use on my project. I can't seem to understand how this EMDC library is calculating the end result for IRMS which is being sent to the HMI which I don't have access to.  Are the raw values being sent to the HMI as is or is there some conversion happening in-between? How can I extract the Irms to send to my MCU ESP32?



Thanks,
Kaushal

  • Hi Kaushal,

    There are two API calls that are used to calculate the IRMS value you are looking at.

    They are described as follows: 

    The energy measurement library is proprietary, so the implementation of those functions cannot be disclosed.

    Best Regards,
    Brian

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