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AD7978 THD

Question asked by erikk on Sep 9, 2016
Latest reply on Sep 15, 2016 by nchandra



we are working with the ADE7978 in our product and we are trying to measure the Voltage THD using the registers 0xE521 0xE523 and 0xE525. According to the datasheet and some discussions I found on the internet the numbers coming out of these registers are 3.21 numbers which means I have to devide them by 2^21 to get the actual percentage. (Wh are these signed numbers if they represent a percentage between 0 and 100 ?) Whenever I read the registers we get very low figures (magnitude of 0.03 %).  This looks  a little to low for us.

Cou?d you provide us with a way how to interpret these numbers ?


Is it OK to read this registers once every 5 minutes or do we need to read them more frequently and integrate the results over time ?


Thanks in advance