Browsing the internet, I stumbled over an interesting video on YouTube were a guy shows a very cheap ESP32+camera solution to read the analog readout of water meters.
I've followed exactly the download links in the WIKI and descripted and the module works on first try!
here you can see the image taken by the camera and the marked ROIs. In the right part you can see the read RAW VALUE.
As the configuration supports from scratch a data feed to an MQTT server, the integration in my IoT-world was pretty simple.
The watermeter in my home has a gauge down to 100ml - you can see the consumption if you fill a cup of water ...
Better don't look at my mounting solution ...
A little bit tricky was the focus of the lens. Factory preset is focus on infinity - the lens mount is fixed with a little dip of glue.
I scraped off the glue with an EXACTO knife. Then, with a lot of feeling and a pair of pliers with round jaws, I very carefully turned the lens - you don't get a good feeling from this. But it worked at the end.The focus is sufficient.
It is really amazing, what can be done with AI on such cheap ESP32 modules - thanks to the author JomJol!