I've had one of these in my garden for the last two months, and I'm having a really hard time understanding what's happening with this thing. As a quick test, I've got a plant sitt...

I've had one of these in my garden for the last two months, and I'm having a really hard time understanding what's happening with this thing. As a quick test, I've got a plant sitting here, and when I pour water on the soil around the probe, the analog reading on the sense pin (which is the one I have on the far right if the connector faces me) goes down. When the soil dries out, the value goes up. Then at another point on the other side of the plant, the trend is reversed. When I had this in the ground for an extended period, it seemed to switch on me at some point - at first watering the plant would increase the value, but then after a few weeks it seemed to have switched on me. So now, most of the time the value reads close to 1000, and when I spray the soil with a hose, suddenly the value would jump down, triggering my watering system to kick in, which then goes into an endless loop where watering drives the value down further, and the system just stays on. That said, when I dunk the probes into a cup of water directly, they read close to 1000 at the moment. I have tried this with multiple probes, with the same results. It's really simple wiring, I'm pretty confident that I'm not screwing anything up. I have the v2 probes. What the heck is going on with these things?

Am I supposed to pot the chips and connector in an epoxy to protect them? What happens when the resistors and FET get wet, is this part of the problem?

Also, how long could I reasonably expect these to last in 'normal' soil? The one I had outside for a few months has corroded, and a lot of the coating has come off. So now the max value I see is about 400, instead of 1000. I can put a fresh one in there, but if the values it reports are erratic, I can't close the loop around this device.