ph probe

[Dr.big]

Hi

I have now two ph probes, the news one is well calibrated since i checked it in solution and it gives the good value. I put it in the cell along with redox-temp-cond probes. It gives me a ph around 7.8-7.9 witch is a little bit low. My other probe, older that is sitting in an other tank same system gives me ph 8.00-8.10... This one is also calibrated and gives the good value since i also double checked. What could cause the difference? Interference? other probes near by??

[Vinny]

The difference could be a result of the probe age. Since one probe is older (much older?), the reaction timing during the calibration process may be slower. As a result, this older probe may need to be calibrated using a different calibration tolerance.

New or fairly new probes could be calibrated with a calibration tolerance of 1 because their reaction times are quicker.

Older probes should be calibrated with a calibration tolerance of 2 or 3. This setting gives the probe more time to stabilize during the calibration phase.

[Dr.big]

the second probe is 4 years old. It could be the problem.