That's what I was saying there are other ways, but the LM1830 is cheap, just a few components (small caps and resistors) needed, schematic is easy, no design necessary. Can drive an LED or sonalert (sp) alarm with nothing more. KPL wrote: > On Thu, May 21, 2009 at 3:22 PM, Carl Denk wrote: > >> At least what used to be an issues, was DC currents plating out of >> materials, the LM1830 and other water sensing designs I have seen lately >> use AC currents to minimize the plating action. >> >> > > This is exactly the problem with gypsum blocks, used to measure > moisture content of soil in gardening. Solution is to use AC currents, > but it should not be difficult to build a circuit around PIC so very > short measuring pulse could be used. > Measure the time needed to charge some capacitor, and give opposite > polarity pulse after that to remove any remaining charge. > > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist