I'm scratching my head how to monitor an intermittently faulty tamper circuit, the cables are small diameter and aprox 50-60m total at a guess (domestic house alarm tamper).
Measuring with a Fluke it's 55ohms normally closed, there are times it goes open circuit hence setting the tamper alarm off.
So I would like to nerd out by monitoring the circuit resistance and send it to my MQTT/Influxdb/Grafana setup.
Googling brings up several Arduino based ohm meters (example), however not within the range I need (aprox 55ohm closed circuit vs infinity when open circuit). Of course I cannot expect accuracy over such an extreme scale!
The D1 mini has the below voltage divider on the A0, but I can't figure that out, i.e. adding 50ohms to a 200k/100k divider would make absolutely no measurable difference.
So not sure how to achieve this... any tips where to start would be appreciated.
Or maybe I am overthinking this, and I could just use a single pull up/down 4.7K resistor to treat it as a digital input...