On Tue, 06 Sep 2016 12:31:34 -0700, Oren wrote:

"Moisture meters are used to measure the percentage of water in a
given "substance." Pics: https://tinyurl.com/hfnmgmo

Take the kids to a garden/lawn center on a field trip :-)

To much water and plants could die by drowning.

Out here, in California, except in the winter, the moisture has to be
pretty low.

I looked at the first in your list:
https://tinyurl.com/hfnmgmo

It was the DT-129 and it was just for wood (not soil).
http://www.ecutool.com/DT-129-Moisture-Meter_7248.html

But it's too expensive to be practical ($166).
It does seem to simply be a resistance meter though.

I'll bet most of the moisture meters are resistance meters.

Looking at the second one in your list, it's half that price:
http://asungadget.com/shop/wheat-cor...oisture-meter/

But it's a "Wheat corn paddy rice moisture meter" for testing grains.
Still, it seems to be a resistance/conductance meter.

It gives a range of Moisture measurement range: 2%~30%