pH probe giving bad readings

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MDB1029
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pH probe giving bad readings

Post by MDB1029 »

So after installing the RA yesterday and calibrating the pH probe, I am getting fluctuations in the pH being reported. I have seen 1 and 11 to give you a feel for the fluctuations.

I figured this could be to stray voltage, which there is stray voltage in my sump. 10v is what is showing on my multimeter and if i take the pH probe out of the tank it is about 4.5v. I am guessing this should not be happening.

I am not sure where the other 4.5v are coming from, i unplugged everything and have only seen the volts go up when i unplug things.

Any suggestions?
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rimai
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Re: pH probe giving bad readings

Post by rimai »

Do you get stable readings with the probe in a cup with tank water?
Roberto.
MDB1029
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Re: pH probe giving bad readings

Post by MDB1029 »

Testing this now. I did check with the multimeter to see if there was any voltage present in the cup, there is not any.

Could the voltage in the water cause it to give seemingly random readings?

I will post result of pH in cup shortly.
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MDB1029
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Re: pH probe giving bad readings

Post by MDB1029 »

It settled right around 8.1 which is what it was reading initially and most of yesterday. When i turned the screen on today it was just sitting at 1.00 and didn't change at all. Last night everytime i would turn the screen on it would be something different and at first it was going back to 8.1 then it just started dropping.
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cosmith71
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Re: pH probe giving bad readings

Post by cosmith71 »

Low pH readings are usually stray voltage in the tank. The pH probe completes the circuit to ground.

Start unplugging stuff one at a time to narrow it down. A bad float switch can also cause this problem so don't forget about them.

--Colin
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Re: pH probe giving bad readings

Post by MDB1029 »

cosmith71 wrote:Low pH readings are usually stray voltage in the tank. The pH probe completes the circuit to ground.

Start unplugging stuff one at a time to narrow it down. A bad float switch can also cause this problem so don't forget about them.

--Colin
This is exactly what i did. I found nothing which took the voltage away except for unplugging the RA which meant no power at all to anything in the tank.

Is the pH probe completing the circuit what caused me to be able to feel the electricity when i touched the water? I could only feel it on a scrape on my finger.

I am getting conflicting information about voltage in the water and ground probes, which i figure will end up being brought up here. Electricity is not my forte, so i am pretty lost as to where the voltage is coming from, how much is too much for the livestock, how much is too much for the RA, pH probe, and other equipment. Should i put in a ground probe? I have the voltage in my DT as well, which is in a different room of the house a good 40 feet away.

I am just lost as to what i need to do.
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cosmith71
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Re: pH probe giving bad readings

Post by cosmith71 »

The water completes a pathway between the display and the sump, so it could be in either one (or less likely, something in both).

You unplugged all pumps, powerheads, heaters, and float switches? Everything in the tank and in the sump?

--Colin
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Re: pH probe giving bad readings

Post by MDB1029 »

cosmith71 wrote:The water completes a pathway between the display and the sump, so it could be in either one (or less likely, something in both).

You unplugged all pumps, powerheads, heaters, and float switches? Everything in the tank and in the sump?

--Colin
I did. I only have 2 PHs in the DT and some of the things in the pump when i unplugged them the voltage would go up on the meter.

I opened a thread on my reef forum and there is an endless debate going on about the validity and safety of using a grounding probe. And people saying there is always going to show voltage if anything is moving and to only worry about current, blah, blah, blah. It just seems to be going nowhere. So I am hoping to get some insight here.
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Re: pH probe giving bad readings

Post by MDB1029 »

It was suggested that bubbles, especially tiny bubbles coming from my skimmer which is a couple inches away could be giving bad readings, any truth to this?
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cosmith71
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Re: pH probe giving bad readings

Post by cosmith71 »

I don't know. I doubt that's your problem, as my probe is near my skimmer and doesn't have issues.

When you're unplugging and testing, are you using a meter, or are you observing the pH reading? Try going by the pH reading only. Meters are iffy sometimes. Start unplugging things and see if the pH reading normalizes.
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Re: pH probe giving bad readings

Post by MDB1029 »

cosmith71 wrote:I don't know. I doubt that's your problem, as my probe is near my skimmer and doesn't have issues.

When you're unplugging and testing, are you using a meter, or are you observing the pH reading? Try going by the pH reading only. Meters are iffy sometimes. Start unplugging things and see if the pH reading normalizes.
I will try this when i get off work. The problem with this method is it is not always bouncing around. Roberto suggested i try it in a cup of water and i let it stay in there for a good 30 minutes and it stayed perfectly stable withing .01. Then i put it back in the sump in the same spot, and it stayed at the same pH within the .01 until i left for work, so about 1-1.5 hours. When i woke this morning after not checking it for 8 hours though, it was reading 1.00. So i know something is wrong.
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Re: pH probe giving bad readings

Post by MDB1029 »

When i got home this evening, the probe had been in the sump for 10 hours or so and was solidly sitting at 8.2. I checked with the meter and still had the voltage registering about 14v. This seems to fluctuate a bit. I started unplugging things and the probe didn't fluctuate more than .01 the entire time until the only thing plugged in was the pH probe. I also checked with the meter and everytime i unplugged something it seemed to drop about 1v. Everything unplugged it was at 8v. I pulled the pH probe out of the water and the voltage dropped to 3v.

I am still as lost as ever but at least the probe seems to be giving good readings now, not that i ever thought the probe was the problem in the first place.

I will check the pH in the morning again. I need to get the cash together for the wifi adapter asap so i can check it whenever i feel the need. With the wifi i am able to graph the pH as well right? I could be wrong here.
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cosmith71
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Re: pH probe giving bad readings

Post by cosmith71 »

Yep, you can graph the pH.
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Re: pH probe giving bad readings

Post by MDB1029 »

So the probe is still giving steady readings. Since i was having trouble with it before should i recalibrate it?

How often should you calibrate the probe?
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