AVR-Chat

I suppose Zack would have mentioned it - I would think
that dielectric (capacitance) would be the best bet for a single 
parameter to measure.
Two flat parallel plates (INSULATED) for a probe.

Ken


Robert Adsett wrote:

> At 10:41 PM 10/18/2007 -0500, Zack Widup wrote:
>
> >I haven't spoken out about this yet but I thought I'd throw in a few
> >words. I work for a geotechnical engineering firm that has a soils
> >testing lab. I spend quite a bit of time doing all sorts of soil and rock
> >tests, including moisture contents.
> >
> >I never saw it mentioned exactly why the electronic means of measuring
> >soil moisture content was needed or what kind of accuracy was desired.
> >But I can tell you this - there are so many different kinds of soils 
> which
> >all have different characteristics and read differently that you just
> >can't do it with much accuracy.
> >
> >I've worked with silts, clays, silty clays, clayey silts, clays with
> >little to some sand, etc. - I've seen everything you will find on the
> >Burmister and Unified Soil Classification charts. I once had the idea
> >that we might be able to measure moisture content electronically. After
> >spending some time at it, I concluded it wouldn't work. If it did, ASTM
> >would have a techniquue outlined for it. They don't.
>
> Which raises a question, for me at least. Could you usefully measure a
> different parameter. Maybe how easily water can be extracted from the
> soil. That might be more important for plants than the absolute moisture
> level in any case. Hmm, some sort of highly concentrated solution 
> inside a
> permeable membrane and measure the dilution?
>
> Robert
>
> http://www.aeolusde velopment. com/ <http://www.aeolusdevelopment.com/>
>
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>
>