Other Parts Discussed in Thread: UCD3138
Hello,
I am having a problem with the emeter library outputs.
At very light load I get numbers that have no realistic meaning, like if a variable was overflowing. I understand that at light load I cannot expect precision, but the results I am getting are not acceptable (it alternates between for example 10W and thousands of watts).
Initially the problem would start below 20W and after doing several rounds of calibration (and changing the emi_capacitance, see below comments) it improved significantly and now the problem surfaces below 6W.
Except for the no load problem, the measurements are fairly precise, so I think right now I have a good set of calibration coefficients. Do you have any advice on this?
Thank you
FIY: there is inconsistency between the spreadsheet file for the calibration and the app note SLUA744 (April 2015) for the E-metering solution regarding the value of emi_capacitance:
- the app note states that this is the total capacitance of EMI filter + PFC input cap after the bridge
- the spreadsheet says to include only the PFC input cap
Based on my results, it should be the PFC input cap only. Using the total capacitance (also EMI filter X-caps) would give me the numerical errors below at 20W load
Thank you