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Re: pH Meters and Electrodes (long, as usual)
Liquid calibration fluids have a shelflife of 6-12 months, tops.
Refrigeration helps. Aquatic Ecosystems
sells powdered capsules that you add to RO/DI water at your end (why
buy/ship water?). Presumably, they can last indefinitely. I love them. I
use them with a PinPoint pH meter/probe with excellent consistency and
results. ATC (automatic temperature compensation) is worthless. The
difference in pH in the temperature range that supports life is negligible;
in tropical tanks, not even a consideration.
> > George - I keep mine in a saturated KCl solution between uses. I have
> > had mine for a year and it still measures pH 6.3 water accurately. Are
> > your pH calibration solutions old? This can be a problem when
> > calibrating the electrodes.
> Yes they are. I'll tell Karla to get some new stuff.
> It *seems* like the pH 7.0 solution cals the probe OK. Do you know the
> of the problem? Does an older solution make the electrode go wacko? Or is
> just an incorrect pH reading?
> > My pH pen has an automatic temperature
> > compensation and automatic calibration when calibrating the electrode.
> > Do your pH meters have automatic temperature compensation?
> AFAIK, no. That takes a special electrode. I suspect the pens have a
> thermocouple near the electrode for this? Since the aquarium water stays
> constant temp and we make sure the cal solution is at the same temp, I'm
> worried about temperature effects