PlantSmart Gardener's Computer

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

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One of the sowacs members writes:
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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
"PlantSmartô 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.]

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