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ADE7753 Waveform problem - LSB is 0x00 when HPF is OFF

Question asked by Oleksa on Apr 1, 2015
Latest reply on Apr 10, 2015 by dlath

Hi

I have some problem with ADE7753 (and one guy from edaboard too, I copied part of his problem description http://www.edaboard.com/thread325423.html)

 

I have no problem with SPI communication, but...

 

When I do 3-byte reads on the 24bit signed WAVEFORM, I get reasonable values with source Ch2 selected, like 0xFFF481 @ V=-10V

Reading WAVEFORM with source Ch1 selected, I get values like 0xFC7A00, i.e. LSB always 0x00.

 

Reading WAVEFORM Ch2 with swapped ADCs (i.e. with same physical source as before) returns a reasonable value of e.g. 0xFFFC7A.

I found that It occurs when HPF in channel1 is OFF

When HPF is ON, waveform is normal 3bytes, but without dc component. I'm trying to measure dc, and have this problem, I don't know why

 

My settings:

MODE 0x400F or  0x400D

IRQEN 0x8

other registers by default

 

There are dc measurement by ADE7753 thread https://ez.analog.com/message/72336#72336

DC measurements can be made but they are less accurate. To do that, you will have to disable the HPF. The voltage and current range basically are set by the attenuation network and the current sensor respectively.

No word about zero LSB problem

I didn't find anything in datashhets or forums

 

Can you help?

 

Best regards

Oleksij

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