I currently have 15x DS18B20 sensors hooked up to an ESP32 and displaying the data on an IOT board. The sensors are placed in a column of wet soil and I am using conductive pipes to heat/cool the soil inside this column.
In the first 2 weeks of using them, everything was working fine. In the third week, I decided to cover up all the mesh-like holes on the column using bubble wrap (to improve the insulation). This new setup was working great for a few days until one sensor started to behave erratically (ie. it would read the correct temperature and then suddenly jump to -5 degrees and then come back to the normal temperature). I continued using it for a few days and then 12 out of the 15 sensors started to act the same way (see picture below).
Normally, I would say that I f*cked up my sensor with moisture trapped inside the column. But two very strange things happened:
- 12 of the sensors are behaving erratically, but in a NEAR EXACT 'erraticness'
- I shut off my system for 3 days and just turned it back on, now only 4 out of the 15 sensors are being erratic. The rest are reading fine again...
x - time
y - temperature (deg. C)
Grey line - ambient temperature
Blue lines - (supposedly) the correct reading
Red, orange, yellow lines - erratic sensors
Does anyone have any theories on what could be going on?