Question Emon analog: Calibration value different from read value

[mambagr]

(corrected)
Hi
I am testing a Wemos D1 mini with an analog current sensor and the EmonAnalog input.
I am calibrating using a known load (although not a pure resistive load).
The problem is that after calibration (aprox. 1893W), the value pressented in the status page (~2300W) is way off the calibrated value for the same load. If i power the sensor through the 5v instead of 3.3v the read value is ever bigger ~3200W.
I don't think it has anything to do with the type of load as it apparenly calibrates and reads the apparent (pun intended) value.
Am i doing something wrong?
I didn't look at the source code thoroughly because i am sure it was made by more experienced people than me in this area.
The sensor i use is the 30A version of the ACS712.
(https://www.ebay.com/itm/5A-20A-30A-Range-Current-Sensor-Module-ACS712-Module-Arduino-Module-For-Arduino-/272375548296?var=&hash=item3f6ad90988)

[xoseperez]

The nominal calibration value for the 30A ACS712 is 66mV/A or 15.15A/V. That value is not visible in the web UI but you can log to the device (telnet) and query it:

get pwrRatioC

[mambagr]

Using get pwrRatioC i get
$-1

I connect the load, calibrate and switch to status page. Shouln't it show the same Watt that i entered?

[xoseperez]

It should, and the fact that pwrRatioC returns -1 means it's NOT storing the calibration values. Do you click "Save" after entering the values?

[mambagr]

Yep. I also get the "Settings saved".

[mambagr]

Verified with another D1 mini. 'get pwrRatioC' returns '$-1'

[xoseperez]

OK, there was a problem in the EmonSensor. It wasn't recalculating some internal variables based on the stored power ratio, so calibration was not working.

Anyway, I cannot reproduce the issue with ESPurna not storing the pwrRatioC setting. This is the code responsible for calling the sensor class to recalculate the power ratio and the store it:

espurna/code/espurna/sensor.ino

Lines 694 to 697 in ac7bf70

	if (value = getSetting("pwrExpectedP", 0).toInt()) {
	sensor->expectedPower(0, value);
	setSetting("pwrRatioC", sensor->getCurrentRatio(0));
	}

As you can see, the only reason to avoid storing the pwrRatioC value is that the pwrExpectedP is 0.

[xoseperez]

What value do you enter in the "Expected Power" field?