Ph probe reading 0

[ÉricB]

Hello,

I get some weird reading each hour or so on my ph probe....  see 19:55:42 below!

I use this ph probe (https://aquariumdepot.ca/products/americ...e1f5&_ss=r) which is supposed to be a dual junction

I try to calibrate the probe... but still same thing...

any idea?
thanks

Code:

Jan 26 19:45:42 reef-pi reef-pi[401]: 2023/01/26 19:45:42 ph sub-system: Probe: ph Reading: 7.51
Jan 26 19:46:42 reef-pi reef-pi[401]: 2023/01/26 19:46:42 ph sub-system: Probe: ph Reading: 7.479999999999999
Jan 26 19:47:42 reef-pi reef-pi[401]: 2023/01/26 19:47:42 ph sub-system: Probe: ph Reading: 7.51
Jan 26 19:48:42 reef-pi reef-pi[401]: 2023/01/26 19:48:42 ph sub-system: Probe: ph Reading: 7.51
Jan 26 19:49:42 reef-pi reef-pi[401]: 2023/01/26 19:49:42 ph sub-system: Probe: ph Reading: 7.51
Jan 26 19:50:42 reef-pi reef-pi[401]: 2023/01/26 19:50:42 ph sub-system: Probe: ph Reading: 7.51
Jan 26 19:51:42 reef-pi reef-pi[401]: 2023/01/26 19:51:42 ph sub-system: Probe: ph Reading: 7.51
Jan 26 19:52:42 reef-pi reef-pi[401]: 2023/01/26 19:52:42 ph sub-system: Probe: ph Reading: 7.51
Jan 26 19:53:42 reef-pi reef-pi[401]: 2023/01/26 19:53:42 ph sub-system: Probe: ph Reading: 7.51
Jan 26 19:54:42 reef-pi reef-pi[401]: 2023/01/26 19:54:42 ph sub-system: Probe: ph Reading: 7.51
Jan 26 19:55:42 reef-pi reef-pi[401]: 2023/01/26 19:55:42 ph sub-system: Probe: ph Reading: -0.3600000000000003
Jan 26 19:56:42 reef-pi reef-pi[401]: 2023/01/26 19:56:42 ph sub-system: Probe: ph Reading: 7.5
Jan 26 19:57:42 reef-pi reef-pi[401]: 2023/01/26 19:57:42 ph sub-system: Probe: ph Reading: 7.5
Jan 26 19:58:42 reef-pi reef-pi[401]: 2023/01/26 19:58:42 ph sub-system: Probe: ph Reading: 7.5
Jan 26 19:59:42 reef-pi reef-pi[401]: 2023/01/26 19:59:42 ph sub-system: Probe: ph Reading: 7.5
Jan 26 20:00:42 reef-pi reef-pi[401]: 2023/01/26 20:00:42 ph sub-system: Probe: ph Reading: 7.5
Jan 26 20:01:42 reef-pi reef-pi[401]: 2023/01/26 20:01:42 ph sub-system: Probe: ph Reading: 7.5
Jan 26 20:02:42 reef-pi reef-pi[401]: 2023/01/26 20:02:42 ph sub-system: Probe: ph Reading: 7.5
Jan 26 20:03:42 reef-pi reef-pi[401]: 2023/01/26 20:03:42 ph sub-system: Probe: ph Reading: 7.5
Jan 26 20:04:42 reef-pi reef-pi[401]: 2023/01/26 20:04:42 ph sub-system: Probe: ph Reading: 7.5
Jan 26 20:05:42 reef-pi reef-pi[401]: 2023/01/26 20:05:42 ph sub-system: Probe: ph Reading: 7.5

[Rob F]

Hi Eric, I think it might be a setting that needs to be enabled. Can you try the following.

Run the following commands in the Pi SSH terminal.

sudo nano /boot/config.txt

After that a file should open, look for the following line.

dtparam=i2c_arm=on

Under that line add the following line if it’s not there.

dtparam=i2c_arm_baudrate=10000

After that press CTRL + S on your keyboard to save it, then press CTRL + X to exit. Now type in the following command to reboot the Pi or power cycle it.

sudo reboot

If that line wasn't there that will have been the problem.

[ÉricB]

Hey Rob!  thanks for the quick reply!!!

The line as already there and uncommented.

[Rob F]

I was hoping that was it, did it always do this? Do you have anything that was switched around that time that could possibly cause interference? Any chance you have a 10k resistor?

[ÉricB]

It started doing that 20 hours after I plugged it few days back. yesterday, I plugged all my stuff into the power bar and temp probes but the problem was there before.

I should be able to find a 10k ohm resistor.  I can also reinstall reef-pi on another sd card or re-test robo-tank 6.5 to eliminate an h/w fault.

[Rob F]

Interesting. I've seen a few odd issues where the probe was at fault even though I didn't think that was the problem, I'm hoping that's the case again as I don't see many issues with it but anything is possible. If you can find a 10k resistor remove the probe and put one end of resistor in the BNC hole and the other end let it touch the BNC housing. Like that you should get a reading of 6.997 or there about. Let that run for a while to see if it goes away.

[ÉricB]

I'll try that tomorrow and I'll let you know the result!

cheers
Éric

[Rob F]

Sounds good. Cheers!

[ÉricB]

Hey! good and bad news...

Bad: Of course I didn't find my resistor box... I have them for +25 years... but the only time I need them in the last 10 years, can't find them!!! story of my life!

good: I reinstalled a fresh instance of reef-pi and only setup the power bar (to keep reef alive!!) and the PH probe. so far, no "bad" reading in 3 hours... (reading every 15 minutes)

So it looks like a software issues to me and not a H/W issue! I'll keep it running like this for about one day and if it's still good, I'll add temp sensors and monitor for another 24h.

ciao
Éric

[Rob F]

Sounds like our stories are similar. Hopefully it doesn't happen again, it is a good idea to slowly add things, let me know how it goes.

[ÉricB]

small update,  added 1 temp probe. (It was already plugged in, i just added the probe in the temp tab). And there was one bad reading... but not 0, 1ph less that regular reading.. (6.94 vs 7.94) after that all good.

i'll keep monitoring it and keep you posted!!!

[Rob F]

Thanks Eric, it's very unlikely the temp sensor had anything to do with it, I think I'm going to get a few resistors shipped to you from Digikey if you are ok with that? I'm feeling like it's probe related, those other 8 or so dips shouldn't happen either. If we can replace the probe with a resistor we'll know pretty quick.

[ÉricB]

Hey Rob! Don't bother about digikey (and their expensive shipping fee for a 5¢ resistor!!!) I'll re-dig into the garage tomorrow or I'll order a new kit on "bezos store".

ciao

Éric

[Rob F]

I don't want you to have the expense, either way I'll cover half the cost of the kit and if the controller does have a fault I'll cover it all.

[ÉricB]

Hello Rob!
good news: I received my "Brand new and shiny" resistor box!!!

bad news... still 0 (-0.3600000000000003)  from time to time with the 10k resistor!

[Rob F]

Thanks, at least we know it's not the probe. One last thing, I should have mentioned this earlier. What size 12v power supply are you using to power the controller? Any chance you have an extra one to try?

[ÉricB]

I use a new 12v 5A brick. I tried another one, (12v 1.5A) with same results.

[Rob F]

Thanks, looks like that should be plenty. I'll get another board shipped out tomorrow. Are you ok with mounting it in the case? There are 7 screws holding it.

[ÉricB]

No problem about the case. Thanks

[Rob F]

Sounds good. And also do let me know how much those resistors cost, I definitely want to cover that expense.