UPDATE NOTE (July 1999)
This sensor has been renamed the Aqua~pro -
 and if it the same sensor, is capacitance-based,
 not heat dissipation as reported below.

They have a webpage at www.aquapro-sensors.com


Return-Path: owner-sowacs@aqua.ccwr.ac.za
From: owner-sowacs@aqua.ccwr.ac.za
Date: Tue, 9 Dec 1997 18:51:40 GMT
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Subject: Moisture sensor confusion
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Greetings,

    I would like to clear up the confusion between Water Watcher and
WaterWatcher.  They are both soil moisture sensors but use different
technology and are manufactured by different companies.  Also, it was
mentioned that Water Watcher uses infrared.  This is in reference to
some new products coming out - more about this later.

    WaterWatcher is an "electrical resistance" type moisture sensor.

    The following is a description of Water Watcher (WW) - only.

    Water Watcher (WW) is a heat dissipation type moisture sensor that
operates on a proprietary micro-processor using a  "Thermal Mass
Measurement" algorithm.  This updated technology is not affected by soil
salts, fertilizer, pH, heavy soil leaching rains, soil temperature
changes, or nitrates etc. in effluent.  Each WW has a soil Moisture
Control switch that can be set from almost bone dry to field
saturation.  When set, WW looks to this setting and then tests the soil
to see if the moisture level is equal to or greater than the setting.
If it is, WW prevents an irrigation.  If it is less, an irrigation
commences.  All during the irrigation, WW is testing the soil moisture
content.  When it reaches that which has been set on the Moisture
Control switch, it terminates the irrigation.  The depth of irrigation
is automatically controlled - prevents fertilizer from being leached
beyond the root zone and contaminating ground water.

    WW is designed to operate with any standard 24 volt AC 50/60 Hertz
irrigation controller.  Each zone on the irrigation controller will have
its own WW and therefore its own individual moisture control.  This is
useful as not all zones have the same plants or soil type.  Each zone is
separate and if one zone does not need irrigation, it will not prevent
the others from receiving theirs.  Each WW is automatic.  It will only
allow an irrigation if WW senses that the soil moisture is less than
that set on the Moisture Control switch.

    Each WW does not need a long string of wires back to the irrigation
controller. WW is attached anywhere along the wires going from the
irrigation controller to the solenoid operated diaphragm valves.

    So what we have here is an automatic moisture controller interfaced
with a standard irrigation controller.

    I would like to point out that WW measures moisture in the soil
relative to the setting on the Moisture Control switch.  The operator
has the ability to change this setting at anytime.  It can be set to
operate at a specific tensiometer reading, or to follow ET readings.
There is a positive "ON" setting that can be used to command an
irrigation so that repaired pipes can be tested and flushed, etc.

    There is a soil moisture indicator red light.  This comes on when
the soil moisture and the setting on the Moisture Controller disagree
and an irrigation is required.  By rotating the Moisture Control knob,
it is possible to determine how close you are to the next irrigation.
Useful for planning purposes.

    WW's web page is now available on the Internet at
http://www.fishnet.net/~jackh/

    It was felt that many areas do not have electricity available at the
irrigation site, or are unable to access water at will.  For these
situations, we have come up with "Moisture Monitor" (MM).  It uses
pulsating infrared and measures the interaction with water molecules in
the soil.  The more water molecules the more interaction, and this
measurable and repeatable.  Since this is a patentable technology, I
will have to leave the explanation short until all legal obligations
have been satisfied.

    MM is very versatile.  A few of its features are:
    MM gives readings in % soil moisture on an economical, hand held,
data reader.  The % soil moisture is displayed digitally on an easy to
read LCD.
    MM is both analog and digital.  Each MM has its own serial number.
Data can also be taken on data loggers, notebook computers, and solar
powered telemetry units for RF transmission to a central computer.
Since each MM has its own serial number, it is possible to keep a
running history in a standard spread sheet program, with either a text
or graphical display.
MM can be referenced to the soil type it is situated in to give more
accurate readings.
Speed.  MM takes a new reading every second.
MM and WW are both about 3/4 inch in diameter and 5 inches long.  They
are designed to accept a length of 1/2 inch PVC pipe to the back end.
They can then be inserted in freshly irrigated soil without any digging
and the subsequent root damage.

    Now, if you have stayed with me so far, here is your chance to give
some input in the design of a moisture sensor.  We are well along in the
R&D phase.  Software is in the de-bugging stage.  But you may desire a
feature not mentioned.  It might be possible to incorporate it.  MM
should be on the market early next year so if you have any wishes, now
is the time to make them known.

    I appreciate the opportunity in being able to use this forum.  Many
thanks to those involved.  I know it is a labor of love, but it is still
a lot of work.

    Best regards,

            Jack Hillen, General Manager