actually, many of them are very cheap (well under $50 ea.), and very robust chemically and mechanically, and i've never seen one that wasn't electrically robust. see for lots of info on ph sensors in general and models that might be good in a soil enviroment. i'd think you'd want one of the fet based probes for soil ph, but i could easilly be wrong. if the omega site doesn't mention soil ph, ask them, they probably know or can find out for you. Morgan Olsson wrote: >=20 > (Resending from correct personality...) >=20 > pH probes are expensive and chemically and mechanically (and electrical= ly) fragile. I guess the best method is to mix a little distilled water = with the soil, then filter out just the water and measure that. -------- --=20 Philip Stortz--"In Germany they came first for the Communists, and I didn't speak up because I wasn't a Communist.=20 Then they came for the Jews, and I didn't speak up because I wasn't a Jew.=20 Then they came for the trade unionists, and I didn't speak up because I wasn't a trade unionist.=20 Then they came for the Catholics, and I didn't speak up because I was a Protestant.=20 Then they came for me, and by that time no one was left to speak up." -- Martin Niem=F6ller, 1892-1984 (German Lutheran Pastor), on the Nazi Holocaust, Congressional Record 14th October 1968 p31636. _______________________________________________ http://www.piclist.com View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist