WaterMark questions...

[Scott Stephen]

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Dear sowacs members,

I work for a small agricultural consultant company where we utilize
gravimetric sampling, WaterMark and TDR sensors to monitor soil water in
crops.  The WaterMark sensor seems to be a fairly reliable, inexpensive
alternative for farmers and consultants and we have seen an increase in its
use.  We have been using these sensors for a couple of years and have been
comfortable with their use.  Although I have noticed that occassionally we
will get some values that don't seen quite right and when grafted show that
an error occured, usually a value of "0".  The trend that is formed is
sometimes interupted by a quick drop to zero and then back up to the
expected trendline.  All of these readings were taken with the handheld
meter and I was wondering if anybody has ever experienced this problem and
what is the cause.  I am wondering if I am getting a bad connection between
the cable and the meter, as sometimes I can get the meter to give me several
different numbers by 'wiggling' this connection?  Is their a simple way to
test to see if this connection is not working correctly?

I also would like to get some comments on data loggers that can be used with
the watermark sensors.  I am aware of some of the products out there such as
WatchDog, Onset Hobo, and MK Hansen.  The cheapest of these is the Onset
Hobo rugged logger that is a four channel waterproof logger for $169.  I am
curious to know if there were any other loggers that could be used in-field,
with overhead irrigation that would fall into this price range.  For our
purposes the logger would only have to take readings a couple of times a
day.  I don't really know how important it is to have a waterproof logger as
I have no experience with them.

I have noticed that Spectrum is selling the WaterMark sensor with a plug end
that can be directly inserted into the WatchDog logger.  Is this a
requirement for all of these loggers and if it is can I easily attach a plug
end on by own that would work effectively?

Thanks for all of the good discussion.

Scott Stephen
________________________
Scott Stephen
Agrimanagement, Inc.
Phone: 509-453-4851
FAX: 509-452-6760

Web Site: http://www.agrimgt.com
Email: sstephen@agrimgt.com