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ADE7858 - calculating xIRMSOS register

Question asked by DavidX on Feb 16, 2015
Latest reply on Feb 23, 2015 by DavidX

I'm using Application Note AN-1076 Page 6 to set the xIRMSOS register in ADE7858.

 

In = 2,5 A

IRMSn = 284198   (Read from AIRMS register)

 

Imin      = 0,186A

IRMSmin = 20061

 

My calculation:

(20061^2 * 2,5^2 - 284198^2 * 0,186^2) / (128 * (0,186^2 - 2,5^2)) = 350683.51022


350683 -> 0x559DB

I set AIRMSOS = 0x559DB


AIRMS: with 0x00 offset => 804

AIRMS with (AIRMSOS = 0x559DB)  -> 6754 (without any load)

I expected something around AIRMS= 0

 

btw, do i have to calibrate xIGAIN or xIRMSOS first?

 

Calculation on Google

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