# Question about PH controller.



## Fitos (8 Sep 2019)

Hi, I have the WEIPRO PH CO2 Controller, which is one point calibration.
I searched in the internet to understand the difference between one point and the two point calibration.
If I write correctly, with the one point we only calibrate the offset (set the zero (0) value).
With the two points, except the zero point we also calibrate the slope and we have a line passing from PH 7 (zero) and through the PH 4.01. So with my PH controller when I calibrate with PH 7, I set only the zero point. After this, If I put me PH probe in a solution which has PH 4.01, then the line maybe is not passing through the PH 4,01 and eventually I will reed different number than the 4.01.  
If the above I wrote are correct, then my question is. If my PH range in my tank is from 7.5 to 6.0, then with my one point calibration PH controller, will I have a big difference on my readings or the specific slope doesn't change so much at this range??


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## Zeus. (8 Sep 2019)

one point calibration is set using one buffer,  two point calibration is the way to go IMO -rinse in distiled/RO water stink probe in buffer adjust so as close as possible, rinse in distiled/RO water repeat with other buffer. Not used you model  'just check it out'  and you only calibrate it using 7.00pH buffer and done as in link


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## Fitos (8 Sep 2019)

yes I know two point is better. I didn't write this. I just want to understand if my one point cal , can read correctly as low as the PH 4.01 if I calibrated only with PH 7 solution. Am I Reed correct values during the range of 7.5 and 6.5? Is the one point controller loosing accuracy??


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## sparkyweasel (8 Sep 2019)

You could use use two, or even three calibration buffers to check your probe and see how accurate it is. You won't be able to adjust it, but you will be able to allow for any discrepancy.


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## Zeus. (8 Sep 2019)

Fitos said:


> yes I know two point is better. I didn't write this.



Sorry 



Fitos said:


> I just want to understand if my one point cal , can read correctly as low as the PH 4.01 if I calibrated only with PH 7 solution. Am I Reed correct values during the range of 7.5 and 6.5? Is the one point controller loosing accuracy??



I would say no pH meter or controller can truly read a accurate pH, its more of a general indication of the pH. But in the 7.5- 6.5pH it should be acceptable, just re calibrate it frequently in case it starts to drift as it will


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## dw1305 (9 Sep 2019)

Hi all, 





sparkyweasel said:


> You could use use two, or even three calibration buffers to check your probe and see how accurate it is. You won't be able to adjust it, but you will be able to allow for any discrepancy.


I'd do that. You'll probably find a bit of drift at both pH4 and pH10, but not a lot. Because pH is a log10 scale as you move away  from pH7 you tend to get a <"more "accurate" reading">. 

I like the <"instruction page"> link for the WEIPRO, nice and clear. 





Zeus. said:


> I would say no pH meter or controller can truly read a accurate pH, its more of a general indication of the pH. But in the 7.5- 6.5pH it should be acceptable, just re calibrate it frequently in case it starts to drift as it will


That would be my worry. I'm not a CO2 user, but if you were aiming anywhere near the 30 ppm CO2 level? I'd be reluctant to <"rely on it as a controller"> to adjust CO2 levels,

I might start with ~15ppm CO2 (you can use <"2dKH indicator in your drop checker to give you a green colour at 15ppm CO2">). I think this is what @Parablennius does?

cheers Darrel


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## zozo (9 Sep 2019)

The calibration method on 2 or 3 point is to insure the most accurate /least deviation in reading closest to your target.
But the accuracy highly depends on quality. The most affordable home use equiment is of a minor quality materials compared to expensive lab grade equipment.

To determine your accuracy in deviation on 3 point calibration than go as generaly adviced, first calibrate 4 than 7 than 10. After it's done put it back in 4 and or 7 if its a very high quality meter it likely will display correct again. With lower grade you actualy will experience its off again because its calibrated last at 10. If it has a 1% accuracy the difference between 10 and 4 is 6 units. For convinience we could assume the deviation is at least 6% over 6 units difference.

Than how older the meter gets the more inaccurate it will become, the probe is not ever lasting. It will lose accuracy and reaction time over x periode of use. Especialy if in the medium measured and its permanently in salts are added. These salts can and will accumulate and finaly clogg the probe if not maintained correctly.

Than its advicable to do only 1 point calibration and this as closest to you target as possible. Meaning, is your target closer to 7 than 4, calibrate one point at 7. Or if your target is closer to 4 than 7, calibrate one point at 4.

Anyway in our case its always closest to 7.. Than calibrating at this will be most accurate. 4 and 10 are values we never will reach in our aqauriums.

I also noticed over the years on cheaper probes used as permanent meter, when new it contained a thick gel substance as KCl reference fluid. After a year use it was as thin as water. Thus on lesser quality probes this is something to keep an eye on. If the reference fluid is deluted it most likely can't be accurate anymore, even if it still can be calibrated.   Calibration is only an electronic reset on 7 regardles the conductivety value of the fluid.


There for, Ph meters with a shut off featere for CO² should not be used to determine the correct CO² contents.. It should solely be used as fail safe to prevent a CO² tank dump. You will have no reference at hand to tell you how accurate it realy is. Buy an extra hobby grade meter and you'll see 90% chance both will never give the excact same result.  Than make a pick which one you believe.


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## Fitos (11 Sep 2019)

Actually I did an effort today with my water change. I calibrated my probe with the PH 7.0 solution. After I test the PH 4.0 and I found PH 3.82. I also tested with the PH 10 solution and I found PH 9.79.
If I create a slope with PH (3.82, 7 and 9.79), I take 90 mV per PH unit. Probably is wrong but anyway I gave it a try.  



zozo said:


> There for, Ph meters with a shut off featere for CO² should not be used to determine the correct CO² contents.. It should solely be used as fail safe to prevent a CO² tank dump. You will have no reference at hand to tell you how accurate it realy is. Buy an extra hobby grade meter and you'll see 90% chance both will never give the excact same result.  Than make a pick which one you believe.



I try to measure my degassed PH but i don't trust the PH controller. Is there any reliable and not very expencive PH meter so can buy???


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## zozo (11 Sep 2019)

I've collected a few Ph meters over the years pocket versions and controller versions and as said never found a set that gave the same result used side by side. Not even the well known brands such as Milwaukee and Hanna.

But the reliability isn't actualy that much important and an approximate good enough for our purpose. It doesn't realy mater if it is off a few 0.units as long as the tolerance is the same, it still is a relative stable and in reliable enough reading. There for its best to pick 1 meter take it for granted and don't go bonkers over its possible inaccuracy. As said we have no reference at hand to check and or dispute it.

Best is to leave pH for what it is and go with a bubble counter and a drop checker. Fill the drop checker with dKh 4 fluid, than if this fluid turns green your water will contain around 30ppm CO². Set the bubble counter in a stable count to keep this drop checker green from the moment the lights come on and shut the CO² off an hour before the lights go off.

It still is interesting to see what a permanent PH meter will display during this cycle but actualy you can do little with it. Don't let the numbers drive you mad. You still will see Ph go up during the dark periode due to the CO² degassing.

Than 30ppm is a green drop checker and approximately 1 unit Ph drop. Than if you start at Ph 7.5 you will be around 6.5 at a green drop checker. Than if pH 6 is your danger zone gassing the crap out of the fish. Than set the controller to shut off before it ever reaches Ph 6. Make it 6.3 or 6.2.

This way the controller serves its purpose the best, it prevents your fish from beeing gassed and suffocate.

Than there is something a Vendor nor any User manual will tell you.. Only than if the controller and its probe isn't susceptible to electronic interferences. This you can check to first measure your tank water in a seperate container than put the probe in the tank or in line where ever you need to place it. And measure again with all electric equipment turned on. lights. pumps, heating etc.. If you see a difference in result or a fluctuating result than there likely will be a capacitive or inductive current running through your tank exiting via the probe and controller interfering its measuring result and actualy renedering it completely useless.   This you can't know up front, it's a trail and error to find out. Some equipment interferes others don't some controllers are very susceptible to it others less. Its a game play between both that has no norms. If it shoots down to Ph 6 due to electrical interference it will shut off the CO² to early. If it reacts erraticaly to it, it can shut on/off erraticaly.

Thus you have to test it long enough and stay constantly aware of electronic interference and keep an eye on that. A controller needs to be constantly under supervision. Don't trust it straight from the box. If you ever change equipment in or on the tank, check how and if it works on the controller.


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## Zeus. (11 Sep 2019)

zozo said:


> Than there is something a Vendor nor any User manual will tell you.. Only than if the controller and its probe isn't susceptible to electronic interferences. This you can check to first measure your tank water in a seperate container than put the probe in the tank or in line where ever you need to place it. And measure again with all electric equipment turned on. lights. pumps, heating etc.. If you see a difference in result or a fluctuating result than there likely will be a capacitive or inductive current running through your tank exiting via the probe and controller interfering its measuring result and actualy renedering it completely useless.   This you can't know up front, it's a trail and error to find out. Some equipment interferes others don't some controllers are very susceptible to it others less. Its a game play between both that has no norms. If it shoots down to Ph 6 due to electrical interference it will shut off the CO² to early. If it reacts erraticaly to it, it can shut on/off erraticaly.
> 
> Thus you have to test it long enough and stay constantly aware of electronic interference and keep an eye on that. A controller needs to be constantly under supervision. Don't trust it straight from the box. If you ever change equipment in or on the tank, check how and if it works on the controller.



My pH controler jumps 0.10pH when the T5 come on


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## zozo (11 Sep 2019)

I had 2, 1 pocket (forgot the brand) and 1 Milwaukee sms122 controller and both go completely bonkers and erraticaly up and down when i put them in the tank. For the pocket version it's only the pump causing it.. The Milwaukee controller or more to say the probe already goes nuts when a cell phone gets to close. And it's a strange erratic behaivor, sometimes it seems stable than all of a sudden The relays starts buzzing like mad. It has a fixed shut off treshhold of 0.1 and the moment it reaches this it's jumping up and down cuasing a buzzing relay. It happens suddenly without any clear reason and it accosinaly happened when i came close to check on the tank. Than i step away from it the buzzing stops, 1 step foreward it starts buzzing again. Now i'm rather staticaly charged, i always get zapped touching stair rail for the biggest part of my life. But this was a first experiencing a Ph controller react to me comming close.

It also gave a different value in each corner of the tank.

I solved the issue with putting the probe inline outside the aqaurium. Inside the aqaurium it was useless. 

And that was a Milwaukee, not the cheapest equipment the day it launched the market. Milwaukee and Hanna are considered one of the top runners in this equipment. But likely not designed to use in aqaurium with loads of other electrical stuff connected.


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## Fitos (11 Sep 2019)

Zozo you are so right. 
I think the reason we always look for answers in the forums is because there is not the same situation for everyone. 
Maybe my probe is constant, because by lack on my setup, I put it on the only corner which I don't have any electrical equipment near.
In my tank although I have PH controller, I have two drop checkers so i can see more accurate results. 
For anyone interested I paint the back of the DC with white nail polish and I have better reading results.


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