Reef Keeper Light pH probe issues

[Kris 2020]

I have an RKL on my 8-9 year old reef tank. I have a pH probe on it, it doesn’t control anything, it’s just for my information. I bought a new probe in February (BRS brand), calibrated it etc. but it always read a little low. I have a salifert test kit that I use for verification, and the probe would read around 8.11 while the test would show an 8.3.

Of course this bothers me, but multiple calibrations don’t change anything. I started wondering about electrical interference, so I got some of the ferrite cord beads because I figured it could be a cheap solution. I also unsnarled my cables for both the temp probe and pH probe from around all the other cords and carefully bundled and zip tied the extra.

I put the beads in this morning (both ends of the probe wires, is this right?) and recalibrated the pH probe. After calibration it reads 7.01 and 9.99 in the solutions, yay. I put it in the tank and it reads.... drumroll...7.88. Verified with my salifert test that I’m at 8.3 ish. I’ve moved the probe to different areas of the sump, no change. I rinse and pop it back in the calibrating solutions, I get 7.01 and 9.99.

any ideas anyone?? Ugh.

 

[robbyg]

Have you tested the tank for stray AC voltage? It might be a tiny voltage that is causing the issue.

 

[Kris 2020]

Have you tested the tank for stray AC voltage? It might be a tiny voltage that is causing the issue.

I have a grounding probe in the sump, cause yeah that is an issue. Maybe my grounding probe needs to be cleaned or replaced. I haven’t gotten a shock lately but that doesn’t mean much if it’s just a little. Good thought, thank you.

 

[n2585722]

To test for stray voltage get a cup of your tank water and put the probe in there and allow some time for it to stabilize. See if the reading is different than the reading in the tank. Also what module has the pH port in use?

 

[Kris 2020]

To test for stray voltage get a cup of your tank water and put the probe in there and allow some time for it to stabilize. See if the reading is different than the reading in the tank. Also what module has the pH port in use?

I tried what you suggested above, and it was the same reading as in the tank. I am not so patiently waiting for my Hanna ph colorimeter to double check my salifert kit. It wouldn’t make any sense that ph in the display would be different than ph in the basement sump, right? I can’t imagine they would be different, but I do testing from the display and my controller is in the basement.
as far as what module,uhhh it’s plugged into the sl1 module, where it says “ph”. not sure if this is what you mean.

 

[n2585722]

If it was the same that would rule out stray voltage. The reason I ask which module is the SL1 does not have electrical isolation between the probe inputs and the system. The SL2 and SLX do have electrical isolation and are less likely to be affected by stray voltage. How old is the calibration fluid you are using? If one of them is off it will affect the accuracy of your calibration. I also assume this is a new probe. If so how long has it been in your tank water? I would wait a week or two if it is new before I recalibrate it. If that fails you could have a bad probe. If that is not it could be the module but if the module did work before I would be more inclined toward the probe.

 

[Kris 2020]

I got this probe in February. It has never matched my salifert tests. The calibration fluid was bought at the same time, and I have tried several packets and calibrated several times...this is one of those things that I fiddle with when I’m bored. I am leaning toward bad probe or my salifert test being off, which would be weird (I mean it’s a ph test, there isn’t much room for human error). And it’s read consistently low all these months. I don’t use the results to dose anything and the tank seems fine, it just bugs me. Have used this controller for 8 ish years. i think this is my 4th probe, or 3rd, but my first BRS probe.