PH monitor acting up

M

mytdbm

New member
Hi,

A few months ago, something happened with my robo-tank controller’s (v2 hardware) PH monitor. Numbers would swing up and down a lot. Attached is a screenshot shot of my ph monitor. Any idea what causes a swing from 7.5 to 8.5? Is it a prob or prob controller on robo tank? Thanks
 

Attachments

  • IMG_5598.jpeg
    IMG_5598.jpeg
    145.8 KB · Views: 3
Sort by date Sort by votes
mytdbm said:
Hi,

A few months ago, something happened with my robo-tank controller’s (v2 hardware) PH monitor. Numbers would swing up and down a lot. Attached is a screenshot shot of my ph monitor. Any idea what causes a swing from 7.5 to 8.5? Is it a prob or prob controller on robo tank? Thanks
Click to expand...
Hi @mytdbm yeah something is definitely not right, how old is your probe? I have seen some odd results with bad probes in the past so it's possible that's the issue.

Have you connected any new equipment recently or added to your system?

Any chance you have a 10k resistor? If so unplug the probe and put one end of the resister in the center hole of BNC connector and the other end of resistor pressed against the outer ring of the BNC connector, that should give you 7.000 pH reading, if you get that the circuit is ok.
 
Upvote 0 Downvote
Came across this thread when trying to rule out the robo tank from my ph probe failing. I used a 10k 1/2watt resistor and it is giving me around 7.6 pH. like the picture when I touch the resistor from the center pin of the bnc connector the the outer rim. Is this reading ok or is it reading off? This is the original Kickstarter version of the hardware.
Screenshot_20250328-063826.png
 
Upvote 0 Downvote
WhatsApp Image 2025-03-30 at 3.38.30 PM.jpeg



retested it again with a new resistor and took a picture to make sure it was right. left it on like that and the ph bounces from 6.4 to 7.6 with resistor like this. With no resistor or anything in place its still reading 4.032 ph Im guessing that means the ph circuit is toast?
 
Last edited:
Upvote 0 Downvote
performed some more tinkering and bishoptf on humble fish recommended me to put the resistor in place and calibrate it to the 7.0 calibration and keep a eye on it. for the last 20 mins or so it has stayed at a solid 7ph will monitor. hopefully it is just the probe needing to be replaced and not the circuit. fingers crossed.

WhatsApp Image 2025-03-30 at 7.25.13 PM.jpeg
 
Upvote 0 Downvote
xiholdtruex said:
performed some more tinkering and bishoptf on humble fish recommended me to put the resistor in place and calibrate it to the 7.0 calibration and keep a eye on it. for the last 20 mins or so it has stayed at a solid 7ph will monitor. hopefully it is just the probe needing to be replaced and not the circuit. fingers crossed.

View attachment 827
Click to expand...
Very sorry for being so slow, unfortunately I didn't get an email alerting me of your messages.

I'm guessing you had 7.6 with the resistor due to calibration running that was meant for the probe. Instead of calibrating try clicking the erase calibration button. After that you should still get around 7.0. It is normal with nothing connected to get about 4.0.

The connection with the resistor isn't very good, that's likely why it was bouncing around 6 at the beginning. Sounds like you have a good connection now.
 
Upvote 0 Downvote
Rob F said:
Very sorry for being so slow, unfortunately I didn't get an email alerting me of your messages.

I'm guessing you had 7.6 with the resistor due to calibration running that was meant for the probe. Instead of calibrating try clicking the erase calibration button. After that you should still get around 7.0. It is normal with nothing connected to get about 4.0.

The connection with the resistor isn't very good, that's likely why it was bouncing around 6 at the beginning. Sounds like you have a good connection now.
Click to expand...

It's all good. I deleted the calibration and getting a solid 6.990. Thank you for the help as always. Ordering a new ph probe let's see if it decides to cooperate lmao
 
Upvote 0 Downvote
New ph probe arrived and no matter what I place it in it only reads between 7.1 and 7.0 . Deleted Calibration and issue persisted. calibrated again after sitting in solution for 10 mins. Placed into tank and reading would not budge. Grabbed a known working ph probe from a friend and plugged in, deleted calibration and restarted controller. Calibrated probe and this probe is reading at 7.444 solidly. Tested Ph with titration ph is at 8.2. Any recommendations?
 
Upvote 0 Downvote
xiholdtruex said:
New ph probe arrived and no matter what I place it in it only reads between 7.1 and 7.0 . Deleted Calibration and issue persisted. calibrated again after sitting in solution for 10 mins. Placed into tank and reading would not budge. Grabbed a known working ph probe from a friend and plugged in, deleted calibration and restarted controller. Calibrated probe and this probe is reading at 7.444 solidly. Tested Ph with titration ph is at 8.2. Any recommendations?
Click to expand...
That's disappointing, I don't know what could be wrong with it as you're getting expected values with the resistor and without anything connected, that indicates the circuit is ok or at least it always has in the past. With the new probe what do you get without calibration? What kind of calibration are you doing, 1 or 2 point? What buffers are you using? It's important the first buffer is 7.0 and the 2nd is 10ish. Using 4.0 can cause issues.
 
Upvote 0 Downvote
Rob F said:
That's disappointing, I don't know what could be wrong with it as you're getting expected values with the resistor and without anything connected, that indicates the circuit is ok or at least it always has in the past. With the new probe what do you get without calibration? What kind of calibration are you doing, 1 or 2 point? What buffers are you using? It's important the first buffer is 7.0 and the 2nd is 10ish. Using 4.0 can cause issues.
Click to expand...

So I have tried both 1 and 2 point calibration. I use 7.0 and 10.0 buffers. I have two sets of buffer mixes one came with my pH probe and one I bought off of Amazon. I tried both buffers deleting calibration between attempting a new set.Without calibration on the new ph probe It stays pegged at 7.10 with calibration nothing changes. With my old pH probe I'm getting 7.4 - 7.6. with calibration. Without calibration it stays at 7.6ph. I always start with the 7 and then the 10.
 
Upvote 0 Downvote
Tried again tonight with a calm patient head lol deleted calibration. Restarted the robotank.Calibrated new ph probe with 7 and 10 again. Now my readings are bouncing all over lol
I think I may be at a loss myself I don't know what else to try other than getting a new controller lol maybe this old faithful has given up the ghost.

Here is a video of it

 
Upvote 0 Downvote
xiholdtruex said:
Tried again tonight with a calm patient head lol deleted calibration. Restarted the robotank.Calibrated new ph probe with 7 and 10 again. Now my readings are bouncing all over lol
I think I may be at a loss myself I don't know what else to try other than getting a new controller lol maybe this old faithful has given up the ghost.

Here is a video of it

Click to expand...
Honestly it doesn't feel like a bad circuit but anything is possible. What do you get when reading the 10 buffer? Did you happen to get one of those cheap probes in the black case with the buffers? I see it bouncing around in the video, I've definitely seen that with faulty probes or electrical noise coming from the water. Did you try putting water from the aquarium in a cup and measuring it? That would eliminate the electrical noise. The resistor test you used provides 0 mV on the circuit which is 7.0, as it's rock solid that indicates the circuit is ok, it would have bounced around with that if the circuit was bad. When you plug in the probe does the BNC feel loose? Maybe it's a bad connection. If you have a small screwdriver you can collapse the hole in the BNC on the circuit to make it tighter. I've seen a lot of strange issues with pH and it's never been the circuit after testing with the resistor. Also without the resistor or probe you get 4.0 which is exactly what you should.
 
Upvote 0 Downvote
Rob F said:
Honestly it doesn't feel like a bad circuit but anything is possible. What do you get when reading the 10 buffer? Did you happen to get one of those cheap probes in the black case with the buffers? I see it bouncing around in the video, I've definitely seen that with faulty probes or electrical noise coming from the water. Did you try putting water from the aquarium in a cup and measuring it? That would eliminate the electrical noise. The resistor test you used provides 0 mV on the circuit which is 7.0, as it's rock solid that indicates the circuit is ok, it would have bounced around with that if the circuit was bad. When you plug in the probe does the BNC feel loose? Maybe it's a bad connection. If you have a small screwdriver you can collapse the hole in the BNC on the circuit to make it tighter. I've seen a lot of strange issues with pH and it's never been the circuit after testing with the resistor. Also without the resistor or probe you get 4.0 which is exactly what you should.
Click to expand...


Tried collapsing and still showed same issue. With both pH probes. Ended up ordering a mc120 Milwaukee pH monitor to confirm working probes and put this doubt to rest lol. Using the Milwaukee probe I confirmed it reading on the monitor than plugged it into the robo tank and the probe was reading dead on , on both the monitor and robotank. So it turns out I got two of those pH probes that were faulty. I had purchased 4 in the past with no issues and these two were dead on arrival. Milwaukee is the way to go with pH probes. Thank you for all the help in trouble shooting as always. @Rob F your the best!!



Screenshot_20250406-221601.pngPXL_20250407_021335549.jpg
 
Upvote 0 Downvote
xiholdtruex said:
Tried collapsing and still showed same issue. With both pH probes. Ended up ordering a mc120 Milwaukee pH monitor to confirm working probes and put this doubt to rest lol. Using the Milwaukee probe I confirmed it reading on the monitor than plugged it into the robo tank and the probe was reading dead on , on both the monitor and robotank. So it turns out I got two of those pH probes that were faulty. I had purchased 4 in the past with no issues and these two were dead on arrival. Milwaukee is the way to go with pH probes. Thank you for all the help in trouble shooting as always. @Rob F your the best!!



View attachment 832View attachment 833
Click to expand...
Ah right on, those cheap probes can definitely be hit or miss.
 
Upvote 0 Downvote
Back
Top