I have my SG3 system working with 5 sensors. I'm wondering if there are any resources/guidelines/opinions about what is a "good" moisture %. For an outdoor plant I'm seeing it settle between 15% and 25% although the soil feels relatively moist and what I would like to see it stay at through the summer. I know the default alarm is around 15%, but that's just a number in code.
I can just water it as I always did and track the number and set around that, but 15% is pretty low relative to full scale. I did a "drop it in water test" and it only went to 85% - 85% so I was wondering if there was some kind of zero/full scale calibration I need to do.
I got the app that supports the sensor itself for IOS and confirmed it's reading the same thing so it's not a code problem. I also put multiple sensors in the same pot and am getting the same readings within a few % so it's not the issue of a "dry pocket" in the soil. I also see it shoot up to 40% when I water it, but it quickly falls back down.
I'm fine if this is realistic, just want to be sure I'm not doing something incorrect.
Ignore 10:00 to 14:50 in the chart, the system was off so dash just drew the straight line.
I have been playing with that same question, and have found that different soils give different readings. The more compact the better the contact with moisture, and the higher the reading. Clay-ish soil moves water to the center of mass, whereas peat moves it outward where it reads better. Likewise, the center of the pot will usually read slightly higher than the outside, particularly in plants which have many lateral roots or rhizomes, as opposed to taproots or tubers.
My most clay-ish, bark-rich and compacted soils read in the 30's, where my "backyard-like" soils tend to hover around 10-15. My loose and sandy soil plants and few-rooted plants like cacti seem to stay in the 3 - 6% range once the excess water drains out.
As an example: I have a 2x4' raised bed, on legs with good drainage and mulch-rich soil. It has sat in the rain in Oregon all winter and right now the center is at 25 and the edge is at 21% I wouldn't want to get my bed any more wet than it is. I have a peperomia and a monstera delisiosa (both indoor) that are both at 44 and feel slightly dryer to the touch than the edge of the raised bed, but both have more granular soil with more vermiculite than the bed which has none.
I think that you are working out your parameters correctly, and it will just take some experimentation for each soil type.