PlantSmart Gardener's Computer

[owner-sowacs@aqua.ccwr.ac.za]

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A contributor writes:
===8<==============
Hi Bruce,

A remaining question I have about these [bimetallic] sensors is: which metals are used and
why?


What a great list!  A chap can ask a question and like magic, gets the answer.

Regarding the bimetalic sensors, I found a little more info on Takemura.  They
have two models it seems.  One is the DM-15 which is the one you have pictured
on the website.  It sells for about $50 when purchased directly from the
company.  They also have a smaller model called the DM-7 for $25 (their prices
are in yen, so these are approximations).  Their website and U.S. distributor
are given below:

Takemura Electric Works
Tokyo, Japan
http://www.demetra.co.jp/

US Distributor:  Kel Instruments Co., Inc.
Address:  P.O. Box 54, Wyckoff, NJ 07481
Tel:  (201)-847-8353
Fax: (201)-891-8113
Contact:  Mrs. Jeanne Rothman

As for the PlantSmart unit, it uses two metals instead of the three metal used
in the DM-15.  



On Wed, 21 Aug 2002 22:01:22 GMT owner-sowacs@aqua.ccwr.ac.za wrote:
>
> Garry Boyd writes:
> 
> ===8
> Sent: Tuesday, August 20, 2002 5:43 PM
> Subject: PlantSmart Gardener's Computer
> >
> > One of the sowacs members writes:
> > ===8 Hi Bruce,
> >
> > some friends and I are studying automatic
> irrigation systems and  are
> > curious about an inexpensive moisture sensor
> sold by various companies.
> It's called
> > "PlantSmart?Gardener's Computer" and it
> retails for $30.  Having looked
> at the variety of techniques
> > for measuring soil moisture (gypsum blocks,
> TDR, capacitance,
> tensiometers,
> > etc.), I am not sure what technique this
> product uses.  Do you know or can
> you
> > suggest a method of finding out?  The link to
> the product is given below:
> >
> >
> http://www.brookstone.com/shop/product.asp?product_code=235416&world_code=3&;
> category_code=35&subcategory_code=478&search_type=subcategory
> >
> > Thanks for your help and for hosting this
> discussion forum.
> >
> > [Bruce comments:
> > There  are several manufacturers of this type
> of unit targeted mainly
> > at  the  home  market. They magically produce
> a digital readout of not
> > only  soil  dryness or wetness but this model
> does pH and light levels
> > too. They are sold without any explanation of
> measuring technique, range,
> > accuracy  or reliability, all of which we are
> interested in and need to
> > know in order to be able to use with
> confidence.
> > If  anyone  can  shed  any light on how these
> units work, please share
> > with the group.]
> >
> > ===8
>
> ===8

===8<===========