Randy Holmes-Farley
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My Tank Thread
Lasse is correct that if there is only one adjusting screw, it is only one point calibration. 
I discuss using and calibrating pH meters here:
Aquarium Chemistry: Measuring pH with a Meter
https://www.advancedaquarist.com/2004/2/chemistry

I discuss using and calibrating pH meters here:
Aquarium Chemistry: Measuring pH with a Meter
https://www.advancedaquarist.com/2004/2/chemistry

