View Full Version : pH Calibration?

06/05/2011, 10:47 PM
Did anyone have problems calibrating their new pH probe? I have calibrated mine 3 times and it's still around 0.40 higher than the correct reading.

06/06/2011, 02:29 PM
How are you determining the "correct reading" = checking with a packaged standard? When your calibrating did you use 7.0 and a 10.0?

06/06/2011, 04:11 PM
I did use 7.0 and 10.0 pinpoint packet solutions. After calibrating with the Apex and washing it down. I put the probe about into the 7.0 solution and it reads around 7.40 and in the 10.0 solution reads about 10.40

06/06/2011, 04:21 PM
It should be a lot closer than that - at worst .01 or .02 off after calibration.

Are you giving it enough time to settle when calibrating?
Are the calibration fluids at the same temp?
Is the probe clean?
Is this a Neptune probe or 3rd party?

06/06/2011, 05:54 PM
Try shaking it up ( gently) - sometimes air bubbles can stick taking the probe in and out of solutions.Ya, new probe should be more accurate than that- I just calibrated a new probe= right on.

06/06/2011, 09:33 PM
It's a new Neptune probe that I purchased about a month ago from Premium and just started to set it up.

About 8 mins calibration time for each packet. Matched temp with tank water. And swirl it a few times during calibration as directed.

06/06/2011, 09:48 PM
I've had a lot of problems and needed to manuallt set the slope and offset using s hidden menu. I've got an earlyflight to wake up for so cant oost more detail until later.

06/07/2011, 08:06 AM
I had many many attempts at calibration that all failed in the same way. I would use the 7.0 and let it settle, <enter>, use the 10.0, let it settle, <enter>. Done. Test the 7 & 10 and they would be significantly off. WTH. I'm doing the process correct.

I tried this many times with the same failures.

After talking with Curt, he showed me a hidden menu that was in the testing menus somewhere that you could hit up/down/up/down/left/right and you would get into the calibration data points. I could then tweak the offset and slope to manually calibrate.

I ended up doing this so many times that I bought a pint of each cal solution. You need to be careful about cross contamination for each re-dip.

06/07/2011, 08:47 AM
Bummer - My new probe was a cheap one from BRS - worked perfectly. Glad I did not have this problem.