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Original question:

MSP430F6779A: Three Phase Energy meter calibration sources

MSP430F6736A: calibration of energy consumption by load in EVM430F6736 development board.

user5961265
Prodigy 250 points

Part Number: MSP430F6736A
Other Parts Discussed in Thread: MSP-EM-DESIGN-CENTER

Hi All,

I'm working with EVM430-F6736 energy meter. Software part: For calibration of energy, to set  the energy threshold like (#define ENERGY_100MWATT_HOUR_THRESHOLD              (SAMPLES_PER_10_SECONDS*3600L*10L)). If the accumulated energy is greater than this threshold means, energy consumed to be incremented. The accumulated energy attained the threshold level for every 10 seconds. How the energy threshold is fixed?.  ( I referred the EVM development board document. As per the document, this threshold calculation isn't same. In document, it takes samples / sec. Here in this software, samples per 10 sec. )

Thanks & Regards,

Anitha.L

  • 0
    TI__Mastermind 49692 points

    Hello Anitha,

    Thanks for your post. Please keep in mind that the legacy Energy library has limited support moving forward and for all new projects, we recommend that you use the Energy Measurement Design Center and software library (MSP-EM-DESIGN-CENTER) instead.

    To answer your question, the ENERGY_100MWATT_HOUR_THRESHOLD define is the accumulated power value that represents 100mWHr of energy and is equal to 100 times the number of ADC samples per hour. This is because the energy gets accumulated at the same rate as the ADC sample. Also the power gets measured in 1mW increments. So, dividing the 100mWHr threshold by 1mW equals 100. Unfortunately, I'm not the author of this code, but it seems like SAMPLES_PER_10_SECONDS is defined as 10 times the sampling frequency perhaps to save divisions throughout the code (perhaps there are more default units of 10mX where dividing by 10mX wouldn't be necessary). Here, SAMPLES_PER_10_SECONDS is used along with another factor of 10L to achieve the scaling factor of 100. The 3600L converts between seconds to hours since the samples are per second but energy has units in hours.

    Regards,

    James

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