STM32 Calibration

I was pondering the question of calibration etc over the past few days (arising from this thread).

Now that we seem to have moved away from a constructors’ website and more towards a ‘plug and play’ scenario, there’s a need to either remove the requirement to calibrate altogether, or to make it easy, not requiring specialised knowledge or more hardware - hence the suggestion of a calibration-free sketch for the emonTx and emonPi that would move calibration into emonHub.

In the process, I was wondering whether the STM32 could have some form of easily accessible user interface, on which to perform calibration? (For the moment, I define ‘easily accessible’: Using a web browser interface, not needing a programmer.)


As starter of the mentioned thread, I agree 100%.
When I bought this stuff (emonTX, emonbase), it was not clear for me, that I have to install Arduino IDE, change the sketch, recompile it and bring it back to the emonTX. As I am somehow engaged in this matter and had good help here (called Robert), I was able to manage it.
But, as Robert wrote, it is highly recommended, that user can change all this calibration and adapt things easily (e.g. on a web interface). Otherwise, openenergymonitor will remain a platform for some specialists.
Being a electrical engineer, I am deeply impressed about how exact e.g.: the 3 phase power calculation is implemented. I come to a failure of < 1% out of the box (only Vrms reference needed to be calibrated).

So I believe, that this excellent tool should get more importance in the market but this needs more user friendly UI.

You all did such a great job, don’t stop before the finish line is reached!

Thank you guys!

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Yes, given its potential for accuracy it would be a great shame if it all got let down by lack of calibration.

The ADC/DMA approach allows for true continuous monitoring of every channel forever. Currently the demo shield firmware does 8,376 samples/sec per channel (3V + 15I) continuously and is just 35% occupied. Admittedly it’s a long way from a complete implementation, especially in the area of phase correction, but it gives an indication of the processing power available.

It might even be time to introduce a distinction between true continuous monitoring, and round-robin continuous monitoring which I think is all that’s been possible with the less powerful hardware (AVR or ESP).

And my main point was that might only be due to unnecessary obstacles that made it so hard that the end user loses interest.

We might be into a race of superlatives there - like brands of washing powder a few decades ago. :rofl:

emonLib, emonLibCM, emonLibTCM… :roll_eyes:

The CM library does get close (the closest yet?) - the voltage and current channel readings are interleaved, but there are still only 4 currents and a single voltage.

Given that calibration is a large topic in itself, I thought it best to split this out of the STM32 hardware thread.

Im keen to bring back more of the constructors approach with the STM32 development. Ideally we can achieve a combination of both to suit both those who want to get into the detail, learn the nuts and bolts of the hardware and software design and those who just want something plug and play. I imagine this STM development will start more on the constructors, self-build end of the scale and over time in later more refined versions approach the plug and play solution while maintaining the learning resources that we have developed during the early development stage.

Right now Im still learning the basics of the STM platform :slight_smile: