Since my last post about how to measure the water usage in my household, I’ve moved a few houses, and luckily enough They had all the same type of water meter, where a small grey reflective plate was enough to put the sensor on top of the glass.

In my current house, the water meter design is more or less the same as the others, however, the wheel that is spinning for every one liter of water doesn’t have a reflective area, but an NFC antenna as shown below. The type of water meter is the “Elster V200 PR6P:1”


My existing inductive proximity sensor is not working on this wheel, but after a quick search only the following sensor is doing the job: “LJ18A3-8-Z/AX”. You can directly order it from i.e. Amazon: and will cost around 9 euros including shipping costs:


The sensor looks equal to my other one, but this one is triggering the NFC antenna on the wheel. Although the description tells me it’s an 8mm thick sensor when I received it it was an 18mm sensor. Anyway, the hole in the metal 90 degrees bracket is made a little bit bigger, so the result will be like this:


The benefit of using such a mounting setup is that you are still able to check the water counter on the water meter manually, especially useful when you have to add your counter data manually on an annual basis to the water company.

The wiring of the sensor and how it’s connected to the Raspberry Pi is identical to how it’s described here: