Reading analog gauge values in NodeRED

I need to get the numeric value every 5 minutes from an analog gauge. The gauge looks like this:

I looked in this topic some years ago and asked a question on Stack Exchange: image recognition - Reading a value of a real gauge - Artificial Intelligence Stack Exchange

My assumption was, that reading a simple value of a gauge should be feasible with a Raspberry Pi or cheaper hardware, some software and little configuration. But it seems we are deep in AI here.
Training various needle positions is not possible since I cannot unplug the gauge an make image calibrations with specified analog values.

I'm still interested in a noninvasive solution for reading analog Gauges without installing sensors / additional hardware. Of course postprocessing is done with NodeRED! Ideas are welcome.

Any ideas how to proceed?

Hi @wolfred,

What a coincidence. That gauge looks pretty much like mine at home :wink:

I find your question fascinating, because like you say it is a "noninvasive" approach. So no changes required to the plumbing, no corrosion of the sensor, ...

For example this Github project might be interesting for you: actively maintained, lots of contributors, lots of stars, ...

I have not studied it into detail. E.g. I don't know whether you can train it for another gauge...


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BTW it runs on a cheap esp32, and it can publish the numerical output to an MQTT server (see wiki). So you can easily integrate this into e.g. Node-RED.

It seems to me (see here) that you can do it all via a nice web interface (hosted on the esp32): capture a snapshot reference image from the cam, and draw your regions of interest...

Now it is up to you :-).
Please keep us updated!

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