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Re: Pinpoint PH Monitor --

> - - - Do you have to figure in temperature into the
> readings?   
> Not that I am aware of. The operating instructions don't mention this
> anywhere.

The insturction don't but the packets of calibration fluid are marked
with different values for different temps.  So it would seem that you
would want to take that into account when you calibrate, as best you
can.  But note that the variations are tiny, and probably well within
the margin of "error" when growing plants, computing CO2 levels, etc.

To calibrate, you go back and forth between known-value fluids
(calibration fluids), zeroing in the adjustments until themonitor reads
the fluids properly without adjustment.  As long a you can calibrate an
elecrode with known-value fluids and it will hold the setting, the
electrode is okay.  The  business end of the probe has to stay wet and
supposedly they age too.  So useful life is probably partly a function
of how long the vendor had it on the shelf.  Shop around for price, but
buy form a vendor that turns its stock over often.

The calibration tends to stray over time, but if you recalibrate every
month (roughly) you should be able to trust your Pinpoint readings. 
You can probalby go longer between calibrations but eventually, the
probe will become unreliable (all probes, like politicians, eventually
become unreliable) and if you go too long between calibrations, it
might get farther off than you, or any aquatic gardener, might like.

Scott H.

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