pH probe calibration issues

[110galreef]

Ok, so I calibrated the pH probe according to instructions and definitly waited about 4-5 minutes for the probes to settle on a number for the 7.0 solutio, then rinsed in tap water as suggested. towel dryed it real quick then did the 10.0.

I then rinsed when all done and dipped back in the 10.0 and or 7.0 solution to confirm the correct readings. It read high by .3.....10.3 and 7.3.

So i tried to recalibrate again. Same results. I left it as is? Is this right? Defective probe??

I was getting a pH reading of about 8.41 in the late afternoon and stil 8.41 an hr or so after lights have been off.

I believe the temp correction feature is off. I also floated the pH solution bags in tank water at first. Tamk temp is 78.0*.

 

[110galreef]

I will update morning pH reading. No fuge or reverse lighting scheme either.

 

[schwaggs]

Thats really odd that the probe was .3 off right after calibrating. How old is the probe? Is this probe on an Apex, ACII, ACIII?

 

[HeneryH]

I had the very same problem and ended up manually setting the offset and slope manually to get it right.

 

[110galreef]

pH says 8.47 this morning after lights have been out for 10hrs. This seems way off if it read 8.41 last evening w/ lights on for 7 hrs.

The probe is New. But has sat in Box for a month or so. The date on the cord is Sept 2010. This is for the Apex Unit.

Sound like I need a replacement from neptune?

 

[110galreef]

Oh and it is the Lab grade pH probe if it matters

 

[jf2381]

I have two lab grade probe on mine and 1 read 8.20 and the other 8.15. Always a .5 difference between the two no matter how many times I try to calibrate them.

 

[HeneryH]

I was starting to think I was the only one with this problem. If you search here you'll likely find me posting a year ago about this and getting a bunch of responses telling me how to do the cal process.

If you do the calibration and find that the values are off when you test the 7 and 10 solutions afterward, you an manually adjust the gain and slope values to get them right.

I am not at my controller now but the hidden menu is accessible from the self-test menu and something like up-down-up-down-left-right or similar. If no one else reports back with the correct sequence, I can figure it out when I get back from my business trip.

 

[110galreef]

so readings still way off. I emailed neptune & they said probably a firmware issue. The system is new & I haven't done any updates as I never hooked up to the network. Hopefully this is it. But now I need to order more calibration pkts.

any input?

 

[reefkeeps]

did it help?

 

[110galreef]

I recalibrated about 3-4 times & it eventually worked correctly. The probe would read 7.0 in the 7.0 solution & 10.0 in the 10.0 solution after like the 3rd calibration, then I knew it was reading correct.

I am getting good readings of ~8.0x's in the morning 8.1x's in the evening.