ORP probe calibration 256mV or 400mV?

[william Lutman]

So I ordered calibration solutions, Pinpoint is 400mV and Amazon is 256mV.

Question: which to use, and which is closer to saltwater readings I'll get?

 

[GARRIGA]

Been told that calibrating pH probe at 4, 7 and 10 provides the most accuracy although we don’t ever see values near 4 and at a minimum should be calibrated by 7 & 10 for salt therefore would calibrating at both end points make ORP proves more accurate vs choosing one extreme?

 

[william Lutman]

Been told that calibrating pH probe at 4, 7 and 10 provides the most accuracy although we don’t ever see values near 4 and at a minimum should be calibrated by 7 & 10 for salt therefore would calibrating at both end points make ORP proves more accurate vs choosing one extreme?

ORP Probes are single point calibration

 

[piranhaman00]

ORP means nothing so don’t calibrate

 

[william Lutman]

ORP means nothing so don’t calibrate

I know ORP is a relative measurement, that said they can be calibrated and then will drift with time

 

[Randy Holmes-Farley Verified Community Expert]

I know ORP is a relative measurement, that said they can be calibrated and then will drift with time

Maybe. I think reefers see them drift mostly due to getting stuff on them, as opposed to real calibration drift. It’s not a technique that becessarily requires calibration as it is an absolute measurement, unlike pH.

That said, calibration at any ORP value is fine as long as it is ORP and not related redox values that vary with the standard electrode used.