I vaguely remember that when I read about soil moisture sensors, they all needed to be cleaned and dried after every use. Basically, you couldn't leave them in the soil. Seemed odd to me, but I never dug further into it.
Is that true? If so, that would explain why the sensor doesn't work here, but leaves me wondering why I've seen so many projects try to use the sensors that way.
Many soil sensors use electrical conductivity between two contacts, using the resistance to gauge the moisture. The more water, the lower the resistance. Unfortunately those contacts will start to corrode after being left in a damp (and electrified) environment.
Is that true? If so, that would explain why the sensor doesn't work here, but leaves me wondering why I've seen so many projects try to use the sensors that way.