Unstable zero load value emontx shield

[Bill.Thomson]

@4est

It worked fine for a incandescent light bulb

From the FAQ:

@Bill.Thomson

Q: I’m trying to calibrate my system with a 60 Watt lamp. Why are my readings wrong?
A:

• You need to use a resistive load much larger than 60 Watts, e.g. a 2000 Watt heater.
• Attempting calibration with a motorized load, especially one that draws a substantial amount of current, such as a vacuum cleaner or air conditioner, will not yield correct results.
• See the relevant Learn section

and

@Bill.Thomson

Q: I calibrated my system with a 2000 Watt heater, but my low power readings are still wrong!
A:

• All CTs are inherently inaccurate at low currents. Most are accurate down to about 5% of their max current rating. To improve on that, you’d need a “revenue” grade one, which will be costly.
• When the current is very low, below about 2% of the CT’s max current rating, errors in the analog-to-digital converter start to become significant too.
• See the relevant Learn section

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I mention it because it’s often overlooked despite being in the FAQ.
Hopefully, it’ll save you from a Huh? WTH? What am I doing wrong? etc. moment.