PH probe calibration

[Mydoghasfleas]

So I am trying to calibrate my Neptune PH probe. Using the 7 and 10 PH calibration packs. After calibration I leave it in the 10, and it reads lower than 10...

what the heck am I doing wrong

 

[Mydoghasfleas]

It is reading 9.48 directly after calibration and leaving it in the 10 pack.

 

[AdamNC]

If it's more than a year old it may be possible that you need to replace it. pH probes don't last forever unfortunately. Double junction probes though will last longer than single junction.