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>...
>I have had difficulty with the effects of fertilizer on these probes
>and wondering if the gyp blocks in some way block the fertilizer ions.
>The only information I have on gyp blocks refers to using them with some
>sort of DC resistance measuring device which is attached momentarily.
>
Harry
In our soils gyp blocks last 2 to 3 years. As they dissolve they keep a salt
concentration around the electrodes and should be reasonably unaffected by
fertilizers.
We use AC only to read our gypsum blocks to reduce electrolysis. Also the AC
signal should have no DC component.
>I am interested in the effect of applying AC to the gyp blocks on a
>continuous basis and am wondering what sort of range of resistances are
>obtained. Are the blocks in the process of breaking down while the
>current is applied such that they cannot be energized continuously? I
>am also looking for a commercial source of the blocks. I would run my
>own tests but I'm generally lazy and don't want to needlessly repeat
>what others I'm sure have already done.
>
Don't know, we never applied a continuous AC signal to the gyp blocks, mostly
to save battery power.
With our blocks the resistance at field capacity moisture level is about
1200 ohms, and at the wilting level about 10K ohms.
One source I have in USA is:
Delmhorst Instrument Co.
51 Indian Lane East
Towaco, NJ 07082
Tel: 1-800-222-0638
>From 1994 catalog:
gyp block w/6ft. leads $6.00 USA
w/25ft. leads $9.00
w/50ft. leads $12.50
Good luck!
Keep us informed and if I be of any help let me know
Chuck
|| Chuck Mancuso || i Univ. of Idaho i ||
|| Sandpoint, ID USA || {|} Sandpoint {|} ||
|| cmancuso@netw.com || {{|}} R&E {{|}} ||