gypsum block sensor.  Change every few years.


At 05:16 PM 8/8/2008, you wrote:
>Pretty coarse is fine. The intended application is to remain in place
>rather than being a portable probe. It is simply to provide some
>information back to a sprinkler controller. Target is consumers rather
>than commercial/large ag organizations.
>
>Basically I need something equivalent to a 10 point scale: bone dry to
>waterlogged.
>
>-Pete
>
>On Aug 8, 2008, at 3:51 PM, Grif wrote:
>
> > resistance/conductivity and moisture content do not track well.  I
> > think with what I think I know, simple and cheap go together nicely,
> > but reliably and accuracy may be a stretch.  If the soil type can be
> > characterised and stays stable,,, (like an orchard or vinyard over
> > time), conductivity/resistance may infact work fine.  If it's a
> > portable unit, not sure you'll get to what you need.
> >
> > Units with good resolution seem to be tensioneters, that and his
> > hands are all my brother trusts (ag guy).  Not fast if I remember.
> > The resistance ones seem to use a gypsum block encased resistance
> > element to make sure none of the "other" stuff affects the
> > resistance/ph around the sensor.
> >
> > Seems like the stablization time for any of the commercial ones I'm
> > aware of is measured in hours, not seconds and minutes.
> >
> > What kind of accuracy do you need?
> >
> > -----Original Message-----
> >> From: Peter Loron <peterl@standingwave.org>
> >> Sent: Aug 8, 2008 3:19 PM
> >> To: "Microcontroller discussion list - Public." <piclist@mit.edu>
> >> Subject: [EE] Replacement for L4620
> >>
> >> Can anybody point me to a replacement for the ST Micro L4620?
> >>
> >> http://www.allelectronics.com/mas_assets//spec/L4620.pdf
> >>
> >> I'm looking for a simple, cheap way to reliably measure soil
> >> moisture,
> >> and am thinking about using an oscillating probe to measure
> >> resistance. This chip looks like it has everything I want all in one
> >> tidy bundle.
> >>
> >> Suggestions?
> >>
> >> Thanks!
> >>
> >> -Pete
> >> --
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W. Keith 'Grif'  Griffith
N7IVS 

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