Re: [APD] RO/DI units

["S. Hieber" <shieber at yahoo_com>]

TDS meters are electrical conductivity meters that
automatically make a calculation, based on the
conductivity, for a tDS value. Usually that means
multiplying by a factor between 0.5 and 0.75. The correct
factor depends on what salts and dissolved solids are in
the water. YOu can do the same thing with a conductivity
meter using any value you choose between 0.5 and .075 --
your guess is every bit as good as the factory's, since
it's rare to know just what the make-up is of the solids
and salts in your water.

But either way, a plain conductivity meter or a TDS meter,
you are measuring the conductivity and factored or not, the
value gives you a good benchmark for how much stuff is in
your water, especially when used to assess a DI or RO unit,
since the values should be very low in either case. :-)

I believe Hanna also makes some very inexpensive EC/TDS
meters. It's worth shoppiong around.  BTW, with a decent
EC/TDS meter, the probe should neve need replacement --
don't you wish that were true of the less expensive pH
meters? ;-)

Good luck, good fun,
Scott H.
--- revance at indiana_edu wrote:
> If you have a RO/DI filter you should really have a TDS
> meter. Using one of 
> these is really the only way to know when your DI filter
> is exhausted. I have 
> seen Milwaukee pocket TDS meters for $25... however I
> have not had any 
> experience with them. I do have a Milwaukee pH controller
> and have been happy 
> with it . . .

=====
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