Help with Calibrating PH Probe

3sgterror

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Hello all! I was hoping to get some help with calibrating my pH probe with Reef-pi. To give some background, I am using a Robotank build with the integrated pH board. The pH probe that I am using is the Milwaukee Instruments Probe.

From everything I can tell, reef-pi is getting a signal from the probe. When I go to calibrate I rinsed the probe in fresh RODI and dipped it in 7 calibration fluid. The current reading it spit out was around 12.5. I waited for it to stabilize and hit run. PXL_20210312_053134871.jpg

I took the probe out, rinsed in RODI again, then put it in 10 pH solution. Here the current reading went up a little. I let the reading stabilize again and hit run.
PXL_20210312_053412759.jpg

Now I place the probe into my sump and I'm getting a negative reading. I've tried to recalibrate a couple of times but keep getting similar results. Also whenever I am in the calibration menu, I get current readings in the 12.5 range, regardless of what I previously calibrated to.

PXL_20210312_054022637.jpg
Can anyone suggest a fix to this or why I am getting this incorrect readings?
 
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3sgterror

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So I deleted the probe from the pH tab and re-did it. I ran through calibration again and was getting similar results as the first time.

In 7 pH solution:
PXL_20210312_133510251 (1).jpg

In 10 solution:
PXL_20210312_133622050.jpg

Now I decided to leave it in the 10 solution after complete calibration to verify I was getting accurate readings. It was closer to 10 and flucuated between 8 and 10 but still better than what I was getting.
PXL_20210312_134303685 (1).jpg

At this point I thought for the time being for testing it was close enough. I removed it from the solution, placed it into my sump and it immediately dropped off into the negatives.
PXL_20210312_134407348 (2).jpg

Could the probe be busted? The reading has remained in the negative for the time being, bouncing back and forth between values.

Screenshot_20210312-085653.png
 

Kurtzisa

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the Kcl in the cup was dry or wet?
i have a similar problem with my new probe, so i put it into my sump for a couple of days and now is working perfectly
 
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3sgterror

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the Kcl in the cup was dry or wet?
i have a similar problem with my new probe, so i put it into my sump for a couple of days and now is working perfectly
do you mean the little cap that came on the probe? It looked wet when the probe was in the cap, but when I took it out to set it up, there wasn't a whole lot of solution in there.
 

robsworld78

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@Kurtzisa could be on to something, if the probe tip dries out apparently that can damage them. I've heard soaking in 4.0 can bring life back to them. With that said once I have seen a circuit stuck at 12.5 so it's possible something is wrong with it. If you unplug the probe what reading do you get? You should get about 4.1 or so with nothing connected. If it doesn't read that try deleting probe again from pH tab and add back. That erases any calibration data that might be in the database, if calibration data is there it could read different than 4.1 without a probe.
 
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3sgterror

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I disconnected the pH probe from robotank and check the calibration screen. I am still getting a reading in the 12's.

I also tried deleting the connector itself and reinstalling it and re-creating the pH probe on the pH tab to no avail.

is this a busted circuit or a busted probe? Or something else?
1615594635667.png
 

robsworld78

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Something is right, can you try the following commands in the Pi terminal window.

This downloads a python script
sudo wget -c https://robo-tank.ca/Robo-Tank_pH_Script.zip

This unzips the file
sudo unzip Robo-Tank_pH_Script.zip

This runs the script
python Robo-Tank_pH_Script.py

After the last command it’ll say Enter Command: Then type in the following, must be a capital letter.

R

It should then print out a pH value, if it does you’re connected to the circuit.

Now type in the following command, must be a capital letter. This restores the defaults on the pH circuit.

D

It’ll say query failed but it will have worked.

Now power down the controller and power back up and see if you get 4.1 without probe.
 
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3sgterror

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Ran that script. Got a value based on what you are saying so I think the circuit is working as you mentioned.

1615645737200.png


I rebooted and disconnected the probe and I'm still getting a reading in the 12's. I also deleted the pH probe from the pH tab, but the same is still happening.

could there be interference from other electronics?

1615647246704.png
 

robsworld78

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Something isn't right, it could be interference, I've seen that in the past to. Last time it was air born, a light ballast was causing issues but it could be electrical as well. Is it possible to try the controller on another AC outlet or even better a different room so it's on a different AC circuit? If not maybe try turning off some other equipment that might be running.

The circuit is definitely working or you wouldn't get any number and it appears to move as those images show different values so yeah something is pushing it up. Maybe a faulty op-amp, not sure.

Did it ever work?
 
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3sgterror

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Something isn't right, it could be interference, I've seen that in the past to. Last time it was air born, a light ballast was causing issues but it could be electrical as well. Is it possible to try the controller on another AC outlet or even better a different room so it's on a different AC circuit? If not maybe try turning off some other equipment that might be running.

The circuit is definitely working or you wouldn't get any number and it appears to move as those images show different values so yeah something is pushing it up. Maybe a faulty op-amp, not sure.

Did it ever work?
This is the first time that I am setting it up. I just filled this tank up about a week ago, but purchased this robotank from you awhile ago. You may remember or not but I had an issue with my first where the circuit didn't work.

you ended up sending me a new one and I sent the old one back to you. You helped me to test it all out when I received the replacement, but i just confirmed that I was getting a value. I never had it in water until this week.

All of that help was through email.

I'll try to move some electronics around, turn stuff off, put it on another circuit, etc. and then report back.

Thanks.
 

robsworld78

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Oh no, that's not good. I think I know who you are but can't put a name to you, the other controller was red, I'm actually using it for myself.

I did test that controller for sure so it was working, now I'm thinking it could be interference of some kind. Let me know the results.
 

robsworld78

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I found the message from interference in the past, it was a T8 ballast, when light was on pH went from 6.8 to 10. That sounds about the same increase as you are likely 8ish. Hopefully you have a T8 or similar running.
 
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3sgterror

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Oh no, that's not good. I think I know who you are but can't put a name to you, the other controller was red, I'm actually using it for myself.

I did test that controller for sure so it was working, now I'm thinking it could be interference of some kind. Let me know the results.
Yep that is me. My name is Rob also. The red one is what I sent back to you. I am not running T8's at all. My lighting is two hyrda 26s.

So I tried running the controller off of another room outlet first but that didn't fix anything. So I disconnected everything and brought the controller itself to another room to rule out electrical interference from my other electronics in the tank.

Unfortunately, I am still getting readings in the 12s complete disconnected from everything and in another room all together.

Is this something I can fix?

1615692346921.png
 

robsworld78

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Thanks, something is definitely wrong and quite shocked as I'm sure I put my probe on it and got valid readings. I was able to find our previous messages and see when you got the replacement the circuit was seen with i2cdetect but you were getting ID errors in reef-pi, then you did some deleting of drivers and connectors a couple times and it finally worked but the picture you sent showed 11.x which I didn't realize so the problem was there to begin with.

I was quite surprised with those errors which were unrelated but didn't think much of it as it finally worked. If you're up to it could you try reformatting the SD card and doing a fresh install just in case? Use the install script so drivers and Pi gets setup correctly for controller.
 
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3sgterror

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Thanks, something is definitely wrong and quite shocked as I'm sure I put my probe on it and got valid readings. I was able to find our previous messages and see when you got the replacement the circuit was seen with i2cdetect but you were getting ID errors in reef-pi, then you did some deleting of drivers and connectors a couple times and it finally worked but the picture you sent showed 11.x which I didn't realize so the problem was there to begin with.

I was quite surprised with those errors which were unrelated but didn't think much of it as it finally worked. If you're up to it could you try reformatting the SD card and doing a fresh install just in case? Use the install script so drivers and Pi gets setup correctly for controller.
Yeah I just figured since I was getting a reading with the replacement, I was good to go also. And yes you are correct on all fronts, i rebuilt the database per your instructions last time and that's when it seemed to work.

I'll do a fresh install and see what happens.

Thanks for all your help again! I'll report back shortly.
 

robsworld78

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I should have noticed that but... Hopefully a fresh install works but I'll probably be sending another board. I don't think I'll pay to have that one sent back though, maybe you can make use without pH. If you were having the problem you originally had you could have fixed it now...
 
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3sgterror

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Alright I did a completely new install, but it looks like I am getting similar readings.

Is this anything that I can do or fix on my end?

1615703634208.png
 

robsworld78

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Thanks for trying, not much more you can do, you already reset the defaults in the circuit so beyond that it's either the 3.3v regulator in circuit is putting out more which would definitely affect the output, a resistor or op-amp issue. I'll get one out on Monday, sorry for all the trouble. Are you ok to remove that board from case and drop in the new one?
 
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3sgterror

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Thank you so much. I wish there was more I could do to fix it. I really hate to have you send out another as I know this isn't cheap to replace, especially the 2nd one.

I have to give you major Kudos though. This is not something that you have to do, it has been months since I purchased your product. Much appreciated again on standing behind your product!

One question, when you say remove the board from the case and drop in the new one? Do you mean the whole robotank board? Or just the pH circuit?

If I were to send this current one back, would it be useful to you or could it be fixed? Because I can send this back on my dime. I'd hate for you to be out a whole board.

Thanks again Rob. I recommend your products to other reefers just on the customer service alone!
 
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