Date: Thu, 16 Jan 1997 22:49:28 -0800 From: Steve Tatman <xas69@dial.pipex.com> To: cp@opus.hpl.hp.com Message-Id: <aabcdefg224$foo@default> Subject: re:measuring restivity of water
Hi Zachary
With reference to your problems measuring water resistance:
>I placed stainless steel
>wire sperated at a fixed distance into some R.O. water produced
>by the unit. I then attached my digital multimeter's leads
>to the two pieces of stainless steel wire. To my surprise,
>I did not get a steady resistance measurement diplayed on the
>digital multimeter. Instead, the value kept climbing.
This does sound like the effects of electrolysis as the gas builds up on
the electrodes the measured resistance goes up. Somewhere I have an
article describing a circuit that overcomes both this using short pulses
of alternating current. If you are especially keen tell me and I will try
to dig it out. Bretts point about oxides is probably also true although I
know nothing about the oxidation chemistry of stainless steel. I suppose
you could use platinum wires... but then you could probably buy several
membranes for the same cash :-)
I have looked at those simple pH meters that they sell at garden centres.
Anyone tried them? I think they probably work by having a small galvanic
current developed between two different metals. They are intended for
dipping in every now and then but if you left the probe in constantly
would you then have metal ions being discharged in to the water? I cant
immagine cps enjoying that very much.
The days are beginning to lengthen and there are green tentacled things
unfurling indoors so lets hope we all thaw out soon.
Cheers, Steve
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