Ph Probe reading not right

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Joined: Mon Oct 01, 2018 5:55 pm
PostPosted: Thu Mar 07, 2019 8:21 am
First i would like to apologize for this question because i know there are lots of posts i have searched up about the PH probe calibration and readings. But i could not find my exact issue.

I just replaced my old PH probe (not working, dried up) for a new one. I calibrated using the PH7 and PH10 solutions.

My PH7 is 489
My PH10 is 771

However when the probe sits in the tank water for several hours it does not go above 7.5PH.
I have done PH tests numerous times and the PH is above 8.0 and closer to 8.4.

I ended up hard coding the numbers into the code but it did not change the PH probe readings.

//calibrate PH probe
ReefAngel.PHMin=489;
ReefAngel.PHMax=771;

Am i doing something wrong? How long should i let the probe sit in the solution during calibration? I gave it about 20 minutes for each solution. Seems no matter how long i let it sit in the solution the calibration keeps jumping up/down 1-2 and is not staying steady at a single number.

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Joined: Fri Mar 18, 2011 6:47 pm
PostPosted: Thu Mar 07, 2019 11:05 am
It is normal to bounce around a few digits.
What happens if you place the probe in a cup with tank water?
Roberto.
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PostPosted: Thu Mar 07, 2019 12:41 pm
Do the calibration also without hitting ok but seeing what value it gives you when the probe is still in the tank. A lot of things could impact the probe readings. Proximity to other probes/heaters/etc. stray voltage, bad ground, etc.

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Joined: Mon Oct 01, 2018 5:55 pm
PostPosted: Thu Mar 07, 2019 3:08 pm
When i put the probe in a cup of tank water it went up to 8ph.
Strange because its not even near any equipment in the refugium.
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PostPosted: Thu Mar 07, 2019 3:10 pm
Sounds like stray voltage then

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PostPosted: Thu Mar 07, 2019 7:11 pm
lnevo wrote:Sounds like stray voltage then


Thanks. This is my first attempt a using a PH probe. I'm going to unplug things one at a time and check the PH probe level. Eventually i'll find the culprit if this is the case.

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Joined: Mon Oct 01, 2018 5:55 pm
PostPosted: Fri Mar 08, 2019 5:17 pm
So I can’t seem to find any stray voltage.
I’ll go ahead and put in a grounding probe just to be sure.

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Joined: Mon Oct 01, 2018 5:55 pm
PostPosted: Sun Mar 10, 2019 10:20 am
I hope i am correct to assume a grounding probe will help with this issue.

I placed one in my refugium (where the PH probe is) and one in my main display tank.

Will give it some time for the PH probe to come up in PH. I hope this will solve the issue. I do know any stray voltage i have is minimal and not causing any shock.
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PostPosted: Sun Mar 10, 2019 10:24 am
It can also be voltage leaking from float switches. It's sometimes a very difficult issue to diagnose, but there is some component in the tank that is interfering.

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Joined: Mon Oct 01, 2018 5:55 pm
PostPosted: Sun Mar 10, 2019 5:57 pm
I have a tsunami ATO which has no electronic components in the water.
So far the PH probe still won’t go above 7.6 even with grounding probes installed.
I guess I’ll keep trying to find a solution.

I also do not have a heater. My water never gets below 76°.

Mainly it’s my return pump, skimmer pump, 4 wave pumps and 2 reactor pumps.
I just replaced all 4 wave pumps this week. I have a new return pump on order (jebao 15000). And one reactor pump was just changed (maxijet). The other reactor pump is kinda old but works great so I won’t be replacing that one.

I’ve tested while unplugging each and the voltage change is negligible. Basically voltage generating from water movement.
Plus with the grounding probes there is no more stray voltage in the water at all.

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