�From:�	Jochen Eberhard ("Jochen.Eberhard")
�To:�		sowacs@aqua.ccwr.ac.za
�Date:�	Friday, June 21, 1996  3:54 pm
�Subject:�	SOWACS: RE: Sensors

Hi,
just my comment to the discussion if there is a need for cheap oraccurate 
sensors. 
If I am talking about soil moisture sensors, I am always thinkingin therms of 
irrigation in the field. (I know this is not very scientific). IfI want to know 
the soil moisture I already have a irrigation system in mind witha some acres 
(ha) and a specific crop. In this case it is better to have a lotof cheap 
sensors to monitor the variation of the soil moisture in the fieldthan one 
expensive sensor for just one possition. If I choose the wrong,not 
representative location for this one sensor, the readings will beworse than 
with the inaccurate cheap sensors. 
A other point is that the farmers will not buy the expensivsensors. I am doing 
some research with analoge sensors for tensiometers. They workfine, the 
fertigation of my trials is done perfect by the attached softwarebut no farmer 
would pay 400 DM (~280 US$) for just one of this sensors not tomention the 
other hardware. So for the common irrigation management thesensors should be as 
cheap as possible. I think it is better to install sensors with avariability of 
up to 20% than to not install a sensor with a 100% accuracy.

This is just my opinion (which can be changed by arguments)  :-)

Jochen Eberhard, Germany

:-) Bruce with his "FUKU" message: 
>2/ I am again sending out Marty's appeal for feedback on whether
>there is a greater need for cheap or accurate sensors:-
>In my opinion, the accurate sensors are available, and are
>being used by those who require the accuracy.
>What is not available are some kind of dime-a-dozen sensor
>for use where a large number of samples are required. These
>could be used in parralel with a few more accurate sensors
>to "correct" and so kill both the birds of accuracy and
>increased sampling points with one budget (so to speak).

>MARTY's original message. (Marty perhaps you would post a
>summary of the responses you recieved?)...

>From:	Marty Grogan (ges)
>To:	SOWACS@aqua.ccwr.ac.za
>Date:	Saturday, May 25, 1996  10:25 pm
>Subject:	Re:  Sensor design economics--Your comments, please 
>
>I am developing a soil moisture sensor using a proprietary
>technology and have encountered a delima.  I can produce veryaccurate, stable
>sensors which cost a lot (~US$500) or relatively inexpensivesensors
>(~US$15.00) which operate very much like switches.

>If you have any opinions with regard toprice/performance/flexability
>tradeoffs, I will quickly become "all ears." 
>Also, if you are willing to provide "beta site" evaluations, I
>would like to provide you with such an opportunity.

>Marty Grogan, Owner
>Grogan Engineering Services