Ok. I got a brand new PH 51 and I am still having exactly the same issue. Is it possible that the amount of water affects potiential hydrogen?
When I have the probe in the res and its reading low the reading immediately rises to equal the reading of the sample as soon as the probe is removed from the res (but is still wet). I've noticed that when calibrating (or resting in storage solution), the reading does not change when the probe is removed from the solution until the liquid is shaken off the probe. This leads me to believe that the reading in the sample is the accurate reading. Am I missing something here?
I would appreciate it if some of you would duplicate my method and report you findings. Does your sample have the same reading as a direct reading from your res?
Thanks