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Forum Post: SLAA577 - phase calibration and V->I phase shift calculation

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Hello everyone, I would like to have some information about how the SLAA577 firmware performs the phase calibration and how the V->I phase shift is calculated. I am using a MSP430F67791 micro. Regarding the phase calibration, inside the firmware code a parameter expressed as "phase angle in 1/256th of a sample increments" is used. (I am referring to line 623 of the "emeter-3ph-neutral-6779(A).h" file) #define DEFAULT_BASE_PHASE_B_CORRECTION_LOW 40 /* Value is phase angle in 1/256th of a sample increments. */ What does exactly mean 1/256th of a sample increments? Is it bound to the nominal frequency or to the measured frequency? If, for example, I have as an input to my device, a sensor which cause a current phase shift of -2.7° and a -0.85° voltage phase shift, how do I have to change the calibration parameter? Also, doing some tests, I could see that it doesn't seem to be periodic (eg. 1 and 257 give very different results) Regarding the V->I phase shift, given that the dedicated field is used inside the GUI released within the firmware but I cannot find any information about its calculation, am I right if I assume it to be the arctangent of the ration between reactive and active power?” Regards, Alan

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