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LotR Clown
12/03/2006, 01:38 AM
I was wondering if there was a conversion or correlation between these two mV numbers. I was wanting to calibrate an ORP probe using pH buffers with a know pH mV reading on a scientific pH meter. If there is some other standard that could be used besides buying ORP standard that would be helpful too.
Thanks for any insight.

Kevin

Randy Holmes-Farley
12/03/2006, 09:08 AM
No, you cannot calibrate an ORP probe in pH buffers, unless you add something redox active to those buffers that are intended to make a standard. Better yet is to just buy an ORP standard. There is no good DIY ORP standard.

These articles have more:

Measuring pH with a Meter
http://www.advancedaquarist.com/issues/feb2004/chem.htm

A Comparison of pH Calibration Buffers
http://reefkeeping.com/issues/2005-02/rhf/index.htm

ORP and the Reef Aquarium
http://reefkeeping.com/issues/2003-12/rhf/feature/index.htm

LotR Clown
12/03/2006, 10:02 AM
OK
Thought I would ask since there are portable meters that will do both with the same probe. I thought there was a correlation out there. I am referring to field meters, not any aquarium products.
Thanks for the reply Randy.

Randy Holmes-Farley
12/03/2006, 10:35 AM
No, it isn't the same sensing probe, although they may be attached to the same plastic holder. Glass pH electrodes and ORP probes (usually a metal like platinum) are different beasts. :)