ApexEL low ph reading after getting warranty replacement

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hllb

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I have an ApexEL and the unit wouldn't go into wifi setup mode after it wouldn't reconnect to our wifi. Talked with Neptune and they sent a warranty replacement. Set it up the other day.

The old unit I had had for a couple of months. My ph went from 7.95 at night to 8.3ish during the day. This was spot on most of the time with my manual salifert test (I test ph manually once a week to make sure the probe was still in line). Once I put the replacement unit on line, the ph was reading quite low (7.6ish) so I redid the calibration. It was still a bit low and I wasn't sure I did the calibration correctly (didn't rinse in RODI in between) so I did it again the next day. The probe (same probe as before) is still reading low and no longer matches my manual salifert test. In the last 24 hours, the low was 7.88 and the high was 8.13. This is about .1 off exactly what it used to read and what the salifert test says.

I'm not worried that my ph is low in the tank - I think it's just the reading. Any ideas? I know I've seen old threads on Neptune's forum about low ph readings, but none were due to a new controller unit (typically new probes). I did use Milwaukee calibration fluid (7.01 and 10.01) rather than Neptune fluid. Would that potentially be an issue? I've read that manual calibration is better than the automatic calibration. I have one set of Milwaukee fluid left - should I try the manual calibration? Or just leave it and assume that it's a solid .1 low?
 
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I think the only thing you can do is manually calibrate it, and go with the flow. While the apex is a nice piece of equipment it is not lab grade.
 
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hllb

hllb

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I think the only thing you can do is manually calibrate it, and go with the flow. While the apex is a nice piece of equipment it is not lab grade.
It just doesn't make sense how the same probe would read differently. If it were a different probe, I could understand but seems like the main unit is interpreting the reading differently or something. I wouldn't have expected to even need to recalibrate, but perhaps that was a poor belief.
 

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I use that same stuff to calibrate mine. I bought the 7.01 at a 3:1 ratio with the 10 as I use it to just verify that it is still in the right ballpark. You say it's about .1 off, so is the probe reading about 6.9 in your 7.01 solution? Did you float the pouch in the tank water to make sure they are the same temp?
 
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hllb

hllb

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I use that same stuff to calibrate mine. I bought the 7.01 at a 3:1 ratio with the 10 as I use it to just verify that it is still in the right ballpark. You say it's about .1 off, so is the probe reading about 6.9 in your 7.01 solution? Did you float the pouch in the tank water to make sure they are the same temp?
Since this was the first time I've done this, I didn't validate after calibration. Lesson learned. I thought I saw it reading 9.99 on the 10.0 solution, but can't be sure. I did not temp acclimate the pouches so I'll do that next time, though I've read conflicting things on how much that affects it. Can't hurt though, right? I have one set of fluid left and I'll order more.

So, tips I should do:
1) temp acclimate the calibration solutions
2) rinse in RODI in between solutions
3) use manual calibration rather than automatic and let it sit for at least 5 minutes
4) verify after calibration that the probe is reading the calibration solutions properly
 

Alchameth

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The back of the Milwaukee pouches show what PH at what temp, and it isn't a lot going by that chart, but ya, if it is off anything you can try to help it be more accurate. I never rinsed mine in rodi between, but did before I started the calibration. I do bob and swirl the probe (somewhere between a tornado and a paint mixer) in the pouch while it's calibrating though.
 

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Clip the pouches in your sump right next to the probe locations (so the bottoms of the pouches are submerged). Let them sit for ~5 min to get the temp up. Start the task and follow instructions. Wiggle it around a little in the pouch to ensure there are no trapped air bubbles.
 
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hllb

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I’ll see if I can clip the pouches. It’s a biocube so no sump. I did swirl in the packets periodically. Looks like the temp difference between 68 and 77 is .02 on the 7.0 and .05 on the 10, so that could be part of the issue
 
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Well, this is getting worse the more times I calibrate it. Maybe I need to remove the probe completely and re-add it? This last time, it seemed to have hung when calibrating on the 10.0 and after, when I tested, the 7.0 was reading as 6.93.
 
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Jon's Reef

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After the calibration is complete, I think you have to press the download button (Cloud arrow in the upper right). Also, I would think 6.93 vs 7 is pretty close.
 
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I went into apex local, reset the apex, then redid manual calibration. Now, the test solutions seem to test spot on. Put the probe back in the tank and waiting for it to settle - it seems to take 5 to 10 minutes to fully adjust to a new ph so I'll wait 10 minutes to determine if it's reading my tank right.
 
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I went back and looked at my weekly ph tests compared to the apex. It was typically off by .06 or less. Right now, maybe 15 minutes after what seemed like a good calibration, it says my ph is 7.89 and my salifert test says pretty clearly 8.15. It doesn’t make sense to me that it’s off by that much. I’m out of calibration solution but ordered some more (pinpoint instead of Milwaukee). I’ll watch it for a couple of days. Prior to the new apex unit, my ph generally swung from 7.93 to 8.25. Occasionally it would go higher but never went lower. These numbers were very close to what a manual test would show me so I’m just not sure why it would be so different now that I have a new unit. My last manual check before the new unit was 8.15 when the apex read 8.2 (on 2/1 at 1:08 pm).

77119EBA-A1D6-45F9-A417-FA86FAF9275C.jpeg
 
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After the calibration is complete, I think you have to press the download button (Cloud arrow in the upper right). Also, I would think 6.93 vs 7 is pretty close.
You know, I'm not sure I pressed the button to send it to the apex. I just calibrated my temp probe and needed to do that. Now I'll have to wait for the new calibration fluid to arrive to try again to be sure. Feels like that should happen when you click the done button on the calibration.
 

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Now you got me 2nd guessing myself. All this made me wonder if my probe was on point, dropped it in some 7.01 to check and it was reading 7.13... So calibrated it again and PH dropped .1... close enough, might test it in 7.01 again in a day or two.
 
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So I wanted to post an update. I am out of town and won’t be able to try recalibrating for another couple of days. But interestingly, it seems like the probe needed time to settle in. It’s crept up over the last several days and is almost on par with readings on my old unit. The marked peak is where I was calibrating it. And each day the min and max are creeping up to where it should be.
1C270352-EBC5-442E-BB60-55AFC41450F7.jpeg
 
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