pH sensors that don't have to be calibrated

Katodude

Silver Supporter
Aug 22, 2017
871
West Palm Beach/Florida
So I am shopping around for a pH sensor that I want to mount inline in my plumbing and hook up to my automation system. I really hate testing pH. Everyone one of the industrial ones that I have seen need to be calibrated often. Do any exist that don't?

How do WaterGuru, Phin, Intellichem do it? Or do they need some secret calibration that I don't know about.
 
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jonpcar

Bronze Supporter
Jun 1, 2016
522
Gilbert, AZ
So I am shopping around for a pH sensor that I want to mount inline in my plumbing and hook up to my automation system. I really hate testing pH. Everyone one of the industrial ones that I have seen need to be calibrated often. Do any exist that don't?

How do WaterGuru, Phin, Intellichem do it? Or do they need some secret calibration that I don't know about.
Kato, Atlas Scientific claims 1+ years for calibration on some of their probes.


It seems in their data sheets that setting up one of these is very touchy. Electrical noise must be isolated, no soldering, etc. I am wondering what kind of accuracy we would really need? I would probably be happy with a 6.8 - 8.2 reading that is accurate to about 0.1

I have seen a number of pool projects that have set up and used these Atlas probes...but “radio silence” after they are done with setting it up...in other words, no updates to know if the data received from these probes was actually useful.
 

sean.a.hyde

Well-known member
Jun 5, 2018
96
Pittsburgh, PA
I have seen a number of pool projects that have set up and used these Atlas probes...but “radio silence” after they are done with setting it up...in other words, no updates to know if the data received from these probes was actually useful.
Guilty!
I ran one of these, a thermistor, and an ORP probe last year connected to a Rasberry pi with great intentions of simplifying testing. I even got the electrically isolated whetsone bridge A->D to deal with noise on the tiny voltages that come off the probes. Also, the probes were suspended in the pool (not the piping), under the autocover. The plan was to take a lot of ORP, pH, temp data, and then correlate that with TF-100 measurements of FC and pH to create a mapping.
I even tied the Rasberry Pi into Thingview and could view pretty graphs on my phone.

Essentially, I created a clock. All the values would change (be dominated by) with the sun (and/or temp) and were essentially useless. The ORP was especially useless because of my very high CYA, but the pH probe also was rather useless.

I had grand plans to put the probes back in when I re-did my plumbing this spring using cord grips. At the last second, I chickened out because I was worried about leaks. I suppose these probes that actually have NTP build into the them would've worked, but I had gotten the cheaper probes originally (plus more reading about how the ORP probe is never really going to work well in the presence of CYA).
Instead, I bought a digital pH meter. This has actually worked out quite well since I've been testing more often to dial in my SWCG and I just let the pH reading stabilize while I count drops for FC.

This is the one I want. 3/4” ntp that I can screw into a saddle clamp in my piping. 1 year between calibrations, and a 4 year life expectancy for about $200
What are you going to use to read the probe? I'd be interested to know how it goes... maybe I will be convinced to resurrect my effort next year.
 
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jonpcar

Bronze Supporter
Jun 1, 2016
522
Gilbert, AZ
Kato, make sure you get one of their electrical isolation mounts as well. What are you planning to do about a “testing sampling station” in your piping? Are you setting up some special plumbing or are you just planning to insert it at a random place in your piping...I think the former is required.

My understanding is that pH is not be as finicky as ORP, but you still might have to be careful with the setup. You never want the probe tips to get “dry” for one thing. Not sure if water “movement” impacts pH like some have said that it impacts ORP readings.

just saw that a posting (by Sean) got up before I posted this...will post anyway and then read through...
 

jonpcar

Bronze Supporter
Jun 1, 2016
522
Gilbert, AZ
Guilty!
I ran one of these, a thermistor, and an ORP probe last year connected to a Rasberry pi with great intentions of simplifying testing. I even got the electrically isolated whetsone bridge A->D to deal with noise on the tiny voltages that come off the probes. Also, the probes were suspended in the pool (not the piping), under the autocover. The plan was to take a lot of ORP, pH, temp data, and then correlate that with TF-100 measurements of FC and pH to create a mapping.
I even tied the Rasberry Pi into Thingview and could view pretty graphs on my phone.
Haha Sean...thanks for the confession! This has always been my plan as well. I always assume that with enough data I can solve just about anything...despite all the previous failed attempts. For me...pH and ORP are the last thing I am planning to tackle...possibly. The giant clock “result” is hilarious.

So I’m really hoping that Kato is going to be successful so that it will pave the way ;) for the rest of us. Any advice you can give him will be truly appreciated!
 

Katodude

Silver Supporter
Aug 22, 2017
871
West Palm Beach/Florida
Hmm, the project got more interesting/complicated. So I am also concerned about drying out the sensor. In reading the docs as long as the humidity in the pipes is around 100% the sensor wont dry out. I would think even when the water drains out the humidity in my pipes is probably high enough. Another good excuse to make sure I fix any leaks in the system. Now that I have a VS pump, I could just run the pump 24/7 at 1000 or 1200 rpm and make sure there is always water flowing (need to test the power draw and how much water flow I would get). I could plumb in a bypass like @segalion did (I really dont want to do that). The other problem is I am also really running out of places to put in another probe. I have a little bit of space in one of the skimmer lines (but it gets shut off when I run my spa).

So I could buy this kit for $380.


Which comes with this fancy controller.


Pros

Din rail mount which is nice for my box
Has a fancy LED on it
Has calibration buttons which will be nice in the future

Cons

I dont have 9-30v DC to power it in my box
requires PLC to read it.
Takes up more room in my box which is already in short supply

I might be able to solve some of these problems with the new sequent automation hat, I think it will provide the power I need. I can make some room for the controller but dont have room for another power supply. @cmc0619 (my go to hat guy) any other good ideas on how to solve the cons?
 

cmc0619

Gold Supporter
May 2, 2018
129
Cherry Hill, NJ
I don't think you'd need a true PLC to read it. The signal is sent on a 4-20mA signal. Without looking I believe the megaIO has one of those. The industrial board definitely does. Maybe not having a PLC in there would give you space for a 24V P/S?
 

dschlic1

Silver Supporter
LifeTime Supporter
Oct 5, 2007
627
Valrico, FL
pH probes are very high impedance devices. On the order of 10 to 100 mega-ohms. You need a special high impedance pre-amplifier between the probe and your microprocessor.
 

Katodude

Silver Supporter
Aug 22, 2017
871
West Palm Beach/Florida
I don't think you'd need a true PLC to read it. The signal is sent on a 4-20mA signal. Without looking I believe the megaIO has one of those. The industrial board definitely does. Maybe not having a PLC in there would give you space for a 24V P/S?
Correct me if I am wrong, but I think the industrial board also has a 10v power output as well. It also say 24VAC or 24VDC Power (does not say if that is input or output). So is it safe to say the industrial board will answer all the short comings?

If the industrial board can power the pH transmitter and read the data from the ph transmitter, that pretty much handle all the cons. I can find room in the box for the pH transmitter. Figure out the plumbing issue and I am golden.

All for the low, low price of about $500 just because I hate reading pH. :brickwall:
 

jonpcar

Bronze Supporter
Jun 1, 2016
522
Gilbert, AZ
I was just reading through Segalion’s posts...we left for a trip and I lost track of all the work he was (is?) doing. I really like his pipe setup for the ORP and pH shown in this post (you mentioned it earlier in this thread)...


Kato, I wouldn’t take a chance with that $200 probe of drying it out (relying on humidity) I would take segalion’s advice on that and make sure there is always a pool of water around it. Funny that the entire time I was following Segalion’s posts, I pronounced his name (in my mind) as sea-galleon ... only when I saw his github ID did I realize it should obviously be pronounced Sega Lion.
 
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CRAD_oz

Member
Jan 13, 2020
23
Sydney Australia
Kato
I have successfully installed an inline pH probe on my pipework and have it logging and connected to my home network.
I do have to Calibrate it as it drifts by +/-0.2 every 3 months or so. I'm a bit lazy and and probably should calibrate it more often but I tend to check my pH manually with my test kit while checking my FC. (I installed the probe before I had a good test kit).
The probe I have has a male 3/4 NPT and so I glued in a 1.5" slip to 3/4 tee fitting u/s of my filter. My system is always full so the probe is always immersed in pool water except when remove for calibration.
I was looking at the Atlantic setup before I found this one second hand on a Industrial surplus site or eBay I can't remember now.
I use the probes (ATC) temperature value in the Transmitter and use it display my pool water temperature while the pump is running.
Sorry I don't have pictures on my phone to show you now.
 
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Katodude

Silver Supporter
Aug 22, 2017
871
West Palm Beach/Florida
Ok, I am just about to pull the trigger on this. I think I have a small leak in the heater bypass valve so I am going to order some new o rings for that and take it apart and make sure it is sealed up tight. With that I should not lose prime in the piping to dry out the probe.

For good measure I might just run my pump 24/7 at 1200 rpm, at that speed it barely uses any power anyway.

The only place that I think I have room to put in is one of my skimmer lines. There is always water being pulled in there except when the spa is running but that is only for an hour or two max and it should not dry out during that time.
 
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VinceL

LifeTime Supporter
Apr 28, 2012
244
Newton, NC
I have the Hayward Sense & Dispense system connected to my Prologic system. The system was installed in 2012. I am on my second pH probe and my 2nd ORP probe. I clean them at the end of summer when I remove them and bring them inside and clean them once during the summer. Each Spring when I reinstall them, I usually have to tweak the calibration on the pH probe by .1 (I think 1 year it was .2). Whenever I test the water, I check the pH and compare it to what the Sense & Dispense is telling me. Always within .1 of the water test result. I have no idea about the electrical properties that are required for the probe. I can just say that the pH probe has been very reliable (requiring only 1 seasonal adjustment per year) for many years.

The ORP probe is a bit more challenging given the complexity of how ORP is determined. I replaced the original probe after about 4 years because it didn't seem to change much...like it had lost its sensitivity.
 

jonpcar

Bronze Supporter
Jun 1, 2016
522
Gilbert, AZ
I have the Hayward Sense & Dispense system connected to my Prologic system. The system was installed in 2012. I am on my second pH probe and my 2nd ORP probe. I clean them at the end of summer when I remove them and bring them inside and clean them once during the summer. Each Spring when I reinstall them, I usually have to tweak the calibration on the pH probe by .1 (I think 1 year it was .2). Whenever I test the water, I check the pH and compare it to what the Sense & Dispense is telling me. Always within .1 of the water test result. I have no idea about the electrical properties that are required for the probe. I can just say that the pH probe has been very reliable (requiring only 1 seasonal adjustment per year) for many years.

The ORP probe is a bit more challenging given the complexity of how ORP is determined. I replaced the original probe after about 4 years because it didn't seem to change much...like it had lost its sensitivity.
Vince...any luck after replacement of ORP? Did it make any more sense to you or become more useful? Sounds like your pH experience has been pretty positive...

Kato...I’m rooting for you! Good luck! Are you going with Atlas Scientific?
 
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Katodude

Silver Supporter
Aug 22, 2017
871
West Palm Beach/Florida
Yeah, most likely going with the whole Atlas Scientific kit. I just ordered a 12v power supply to drive it. Will install that this weekend and make sure everything fits before I pull the trigger and order it all.
 

Katodude

Silver Supporter
Aug 22, 2017
871
West Palm Beach/Florida
Well its pouring rain here, and I am a little bored (never a good combination). I just ordered this whole Atlas kit. @cmc0619 will help me figure out how to get my MegaIO card to read it when it gets here.

 
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Katodude

Silver Supporter
Aug 22, 2017
871
West Palm Beach/Florida
ah, how times have changed. I remember when I first started with TFP I said "what $79 for a testing kit!!!!"

Now I just realized I spent $400 just to test pH.

To all beware, this pool stuff is a slippery slope. The quest for absolute control and perfect water becomes and addictive obsession.
 
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VinceL

LifeTime Supporter
Apr 28, 2012
244
Newton, NC
Vince...any luck after replacement of ORP? Did it make any more sense to you or become more useful? Sounds like your pH experience has been pretty positive...
After replacing the original ORP probe, I started getting what to me were more normal readings with the kind of variation that I expected based on chlorine levels, pH and water temperature. With the water at typical summer temperatures (mid-to-upper 80's) and proper pH, I find that an ORP reading in the low 600's indicates the chlorine is around 4 ppm.
 
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Katodude

Silver Supporter
Aug 22, 2017
871
West Palm Beach/Florida
After replacing the original ORP probe, I started getting what to me were more normal readings with the kind of variation that I expected based on chlorine levels, pH and water temperature. With the water at typical summer temperatures (mid-to-upper 80's) and proper pH, I find that an ORP reading in the low 600's indicates the chlorine is around 4 ppm.
Hmmm, this seems interesting. I wonder if I can build a correlation between FC, Orp, CYA, temp and pH. Be nice to have some type of formula to make the ORP reading more useful.