Please help, pH Probe question

[Coral Keeper]

Hello, so I've had a single junction Neptune Aquatics pH probe for several years now, decided it was abiut time to get a new one, so I just purchased a new double junction Neptune Aquatics pH probe, calibrated both with 7 and 10 pH fluids, put each probe in the calibrating fluid after calibration and both probes are spot on, maybe +- 0.01.. then.. i put both probes in the sump and they are both giving different readings.. they have about a 0.07 or more difference.. is this normal?
pH is my old probe and pH2 is the new one.

 

[Lasse]

IMO and with no experiences of these pH probes (but huge expiriences with other types of pH probes) - a new pH probe need a couple of weeks in order to work 100 %. Do a new calibration after 2 weeks and compare. I would not vorry about a difference of 0.07. IMO the second decimal digit is like the chrome parts of old Caddilacs - beautiful to look at but of no importance.

Sincerely Lasse

 

[biecacka]

Similar question here, my return pump died and my ph probe sat in my calcium reactor with no water flow for about 10 days and the probe was reading 3.3 on my apex. I get everything back online and order new solution to calibrate my probe and see if it’s bad. I clean it and drop it in 4.0 solution and it reads 250 3 different times. I drop it in 7.0 and it reads 400 3 times. Confused if it has gone bad or not, I put it back in my reactor so I can continue to run water through it. It jumps up to 8.3 and has now been holding steady around 7.7 for about a day.
probably a good chance the probe is bad? Or should I calibrate it again?

corey