The only things of that sort I'm familiar with are the electrodes used in
blood gas analyzers.  They use a catalyst to accentuate the conductivity
change due to different solutes in the water.  A bit pricey, though, at
$50-300 a throw.

Ken

At 09:16 AM 9/23/98 +0100, you wrote:
>> Anybody have a lead on a cheap but reliable (I want it all for nothing)
>> sensor that measures dissolved oxygen in water?
>>
>A fish?
>
>
>