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> Date: Sun, 3 Aug 97 18:55:37 -0400
> From: Steve Robertson <svr at eecs_umich.edu>
> Subject: Re: Conductivity (was Measuring hardness)
> Would it be possible for Frank to calibrate his conductivity probe/meter
> to HIS water conditions? i.e. it seems to me that he could
> simultaneously measure his water hardness for several different hardness
> levels using an off the shelf test kit AND his shiny new conductivity
> meter. He could then set up a table showing what hardness level
> corresponds to a particular conductivity reading.
This would work if you had a lot of data that established a correlation
between the conductivity changes (at 25C) and the changes in hardness
*and* if you were willing to neglect other possible causes and the
likelihood that you might get changes in hardness with little or no change
Generally, even with laboratory analyses with uncertainties less than +/-
a percent or so and a lot of data, it would be difficult to establish a
good relationship. In real systems there are usually too many other
variables. If you have a smaller data set and add in the poor precision
of hardness test kits, then your chances of establishing a meaningful
correlation become very small.
Better to just use the test kit.