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Re: ADE7758 Watt Gain Calibration

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Hi hmani,

I discovered my problem with the WGAIN computation and now most of the calibration seems to be working.  I was doing some manipulation to keep things in Integer format in the code (bit shifts and the like) and I had introduced a problem there.  I converted most of the code to double precision for the time being, just to make it easier to read and debug.  I don't convert to integer until I actually need to read or write a register.

 

Thank you for your offer of help.  I found the problem when I went back to answer your questions.

 

I do have one remaining measurement that I can't seem to get right - VRMS.  I am not getting a linear response, so i don't believe that VRMSOS or the LSB factor is the answer here.  I am just keeping VRMSOS "0" for the time being - please tell me if that is not a good choice.

 

Also kindly tell me if I should post this under another heading since the topic has changed a bit.

 

After calibration, my VRMS readings are not much different than with no calibration. 

 

At 200mA and 120.4V measured on an accurate meter, I am getting 553000 from the VRMS register which I am converting into 120.9V

 

At 9.8A and 117.3V measured on an accurate meter, I am getting 553550 from the VRMS register which I am converting into 120.9V.

 

The all of the values above are subject to constant slight fluctuations because the line in is not perfect, but they represent averages.  As you can see, I could use offsets to correct one measurement, but the other end would become that much worse.

 

Where would you suspect I still have work to do with my calibration procedure in order to correct this problem?  The Watts, VA and Current are all reading pretty accurately now - VRMS is the only problem.

 

Thanks!


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