Today I learned that my natural gas meter (Honeywell BK-G4MT) can be optionally equipped with an addon device to "read" the current meter value: Honeywell IN-Z61–IN-Z65.
Upon further reading, I learned that this device is just a reed switch that captures the moment a small magnet (that is attached to the rightmost counting wheel) is in its lowest position (the screen reads "zero" for this position).
So I had a brain fart: contact sensors can detect changes in magnetic fields! I attached an IKEA Parasoll contact sensor, and, lo and behold, it really works!
Now I just need to adjust the Parasoll driver to act as a bean counter!
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Oh wow, very interesting. I'd like to see how this hack materializes?
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Just checked local ikea inventory and then went outside to look at my gas meter. Not a honeywell 
but it did make me think: If you move this project forward there may be grateful US Hubitaters whose gas meters measure in cubic feet 
Gas charges here are also broken down into flat fees, distribution fees / unit and fees for the gas unit itself. There may also be tiered pricing depending on the number of units used. You could really create a great tool to help people avoid nasty bill suprises - or at least the suprise bit! Good luck with the project - very neat!
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I wonder if a utility person stopping by would come to the opinion that meter theft was afoot?
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Small update: I created the modified driver here: IKEA Parasoll Pulse Meter (E2013).
I have 2 problems:
- The index in Hubitat lags behind the real value, although I see constant events coming from the device to Hubitat. This could be either because the sensor misses some magnetic pulses (there is a 1 cm gap between the IKEA device and the magnet), or because of the very bad Zigbee signal I get from the device (LQI = 40/255). I cannot add a repeater device closer to the gas meter as that is public space, so I am looking for a repeater with a bigass antenna to compensate
- The theft issue that @velvetfoot raised is something I should indeed be worried about. I wrote an email to the gas distribution company to ask if it is possible for them to install the Honeywell IN-Z61 pulse detector (that I will probably wire to a Badring Water Leak detector instead).
One thing at a time, right now I'm focusing on getting the gas meter index value to Hubitat. Pricing stuff can be added alter, either in the driver code, or in a separate app. Thanks for the idea!
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Yes, diving straight into the gas meter rabbit hole, and I don't even have that meter! LoL
Good luck with the project though I've never given those door sensors a moments thought, but I'm starting to see niche use cases!
Inside those sensors is an actual mechanical reed switch. You most likely need a analog hall effect sensor. A hall effect will have a faster response time. You might be hitting the mechanical limit of that Reed switch depending on the cycle time. You might also have a minimum cycle time that the sensor can see as in it has a cool down period.
Might not be applicable where you are at, but I read my gas and water meter with a SDR stick and RTLAMR. Half the battle is figuring out which ones are yours. But they broadcast a radio signal every so often that you can pick up and decode.
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Same. It reads the wireless transmission from the meter and brings it into Home Assistant, which is then brought into Hubitat. Works great!
Looks like the Parasoll sensor is solid-state.
I have one and swear I could hear it click.
Hmm, maybe your battery is moving a bit when you put the magnet next to the case? 
