pH probe variations

dtaranath

Premium Member
So I recently purchased a new Apex (full model). I had a brand new Neptune standard pH probe I had gotten from someone recently who did not have a use for the extra probe that came with their Apex. Initially worked fine, then all of a sudden, two days in, the pH readings jumped from 8.3 to 8.9, and stayed in the 8.9-9.0 range for several days, but everything in the tank was alive and well.

So I decided to recalibrate the probe. But I also chose to calibrate the probe that came with my Apex also so they can run side-by-side in case this were to happen again.

The problem is, my recalibrated probe is reading 8.2, while the newly calibrated probe is reading 8.66. I recalibrated both probes another two times, and it's still reading the same.

When the water is tested to a test kit, i'm getting around 8.3. Could the probe that came with my Apex be defective? Both are standard grade probes.

I'm going to let both sit in the water for a few days to see if I get a sudden jump like I did when I first set it up.
 

aquamanic

WHO DAT??
Don't check them against each other or your tank water. Calibrate them, then return them to the calibration solutions. They should both read 7.0 and 10.0 in each solution or within .05 of the solution. My guess is one of the probes won't be able to do that. May take a couple of calibrations.
 

dtaranath

Premium Member
you're right.

the probe i just got with my apex is reading 7.33 and 10.2. I just recalibrated it again, and immediately after the calibration, the low was 6.92. So now i'm recalibrating again.

How many times do you think it will need to be recalibrated? this is probably the 5th time this particular probe is getting calibrated.

Crossing my fingers!
 

aquamanic

WHO DAT??
If you've tried 5 times and it still won't read correct, throw it in the trash.

Does your other probe calibrate correctly?
 

dtaranath

Premium Member
yes, it did. I did it a few more times today. The second probe will calibrate, but only immediately after calibration, will it check the low solution around 7.0 and the high solution at 10.0. But the moment I put it into the tank, it registers around 8.4. I then check it against the solution, and it's now 7.15 and 10.1. The first probe, after going through the same procedure, checks out the calibration fluid properly, and gives me a tank reading of 8.15, which is in line with the test kit.

I think I just received a bad probe with the apex?
 

james1990

New member
iv been going through the same situation but with a standard grade and an apex lab grade. By re calibrating the probe over and over it will eventually read correctly? I don't see how..

I can get them to calibrate but once on the tank it will read low after a few days, I'm waiting for a new lab grade from BRS this week. Love spending 70 bucks after 500 on my apex
 

dtaranath

Premium Member
iv been going through the same situation but with a standard grade and an apex lab grade. By re calibrating the probe over and over it will eventually read correctly? I don't see how..

I can get them to calibrate but once on the tank it will read low after a few days, I'm waiting for a new lab grade from BRS this week. Love spending 70 bucks after 500 on my apex

lol, let me know what you find.
 

aquamanic

WHO DAT??
dtaranath - have you tried swapping the probes just to see if the problem stays with the probe jack (which might indicate the controller) or moves with the probe (which you would expect if the probe was faulty)?

Another test - get a cup of tank water and move the probes one at a time into that. Does the reading change (it shouldn't)? If it does, then you might have something bleeding a miniscule amount of voltage into your tank - a broken float, pump, heater...something.
 

dtaranath

Premium Member
well, I tried the cup thing, and no change.

I tried switching the probes, and there you have it. the previously "bad" probe was now normal in the first probe jack, and the previously "good" probe was now off by the same degree in the other jack.

Good detective work! But I guess that means I may have a defective controller. Or, I now have an Apex Lite. LOL
 

TerenceF

New member
Did you set the Apex to use the second port to be pH instead of the default ORP? Don't know if that would lead to your symptoms, but it is important.
 

dtaranath

Premium Member
there's a setting on the apex. If it's in ORP mode, it gives a whole number in 3 digits (xxx). If pH, it carries it out to the hundredths place (x.xx)
 
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