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How precise is good enough for a pH measurement?

Here's one for the scientifically inclined...

Currently, I use a LaMotte pH test kit which is calibrated in divisions of
0.2 pH units. By extrapolation, it isn't too difficult to read the
comparator to 0.1 pH.

I've been considering buying a Hanna Instruments Piccolo Plus pH tester,
which has a claimed precision of 0.01 pH and an accuracy of 0.01 pH. It has
manual 2 point calibration and will automatically compensate for temperature

Years ago, when I was still doing salt water tanks, I picked up an el-cheapo
"pH pen" at a club auction and promptly threw it away due to it's lack of
accuracy (or was it just because I didn't realize that the thing had to be
re-calibrated constantly and I was just too much of an idiot to know any
better at the time?). So I'm rather leery of electronic meters.

Anyway, the Piccolo Plus looks to be a quality piece of equipment and I'm
wondering if anyone with more experience dealing with electronic pH
measuring devices can give me an opinion. I'm favouring it over cheaper
devices due to it's higher precision (0.01 pH for the Piccolo Plus vs. 0.1
pH for most other units). Is the extra precision worth it?

The pH electrode on this unit is replaceable - how long a service life
(given proper storage and maintenance of course) can I expect of the


James Purchase