What ph number to believe

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LoL - I don't want to control anything. I was asking you in the context that you must have precision pH readings.

WHY do you need them (1 tenth accurate readings +/- 0) if you don't have a means or plan to act upon them? This entire thread is a circular conversation based on your need to have precise pH measurements for $1200 an inch coral because that coral grows best at some xxxx perfect pH.


Sorry, but none of this makes sense and instead it goes back to chasing an unimportant level of precision with a non precision instrument. I think we are here because you assumed that one or more of these devices was more precise than it is, not because it matters, but because it bothers you.

Asking again, why do you need to READ pH to 1 tenth of a unit of precision???
First why don’t you continue to elaborate on how ghl’s .1 accuracy claim is rounded down from .2? You have been incredibly rude telling me to go read about significant digits, precision vs accuracy, and all the while you’re completely wrong.

Second we have already established a difference in .2 ph is a 58% difference. If you don’t care about 58% then move on, others do.

Third I don’t care that my ph is at this magical level you speak of. I have said it once I’ll say it again, I want high ph. That can mean 8.2 in the am and 8.4 in the pm or 8.3 all day long. You are the only one bringing up this thought of it staying at a certain level. Although it can be done btw using an apex and a solenoid valve on a co2 scrubber, but I don’t have a magical number other than aim for natural seawater.

And my whole point here is that I have reason to believe one of my probes is off by more. So I want to figure out if I am at ph of 8.3 or 8.0. Which is the difference of where I want to be versus not even close.

And lastly you are the one obsessed with arguing with me on all this in an attempt to derail this thread. Good job mission accomplished.
 
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Pick one of them and use it... stability and ballpark is more important than 1 or 2 tenths of a pH.
Stability might be more important to you. I see absolutely no difference in coral growth with a normal day night ph change. 58% difference between 2 tenths is certainly more important to coral growth.
 
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That is the exact point that appears to be missed in this entire thread.
It is not a true statement. Stony Coral growth is directly impacted by what number the ph is. This is more fact than theory at this point. You are the one missing this.
 

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First why don’t you continue to elaborate on how ghl’s .1 accuracy claim is rounded down from .2? You have been incredibly rude telling me to go read about significant digits, precision vs accuracy, and all the while you’re completely wrong.
I have not been rude at all and apologize if you feel that I have been.

Accuracy is +/- .1 pH unit.

That means if the REAL pH of the sample is 8.1 than the PROBE is capable of returning a value of somewhere between 8.0 and 8.2

That is the PROBE it outputs a voltage to the p4. The p4 takes that voltage and turns it into a digital number between 0 and 1023. That number is filtered and then rounded to a single decimal place. There is no documentation as to how the software does this or if a value of 8.15 or 7.549 is rounded up or down, etc.

Furthermore, what if the REAL pH is 8.123 or 8.149 etc. The tool does not have the precision or significant digits to get you as close as the .1 you desire. It is loosely stated as +/- .1 for that reason.

These are hobby intruments, not lab equipment where all of this would be clearly documented as accuracy, error and precision. (all different qualities of the returned number).
 
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Don't be too quick with your assumptions...

Thread 'Lessons learned in trying to maintain pH stability' https://www.reef2reef.com/threads/lessons-learned-in-trying-to-maintain-ph-stability.871213/
I have basically done everything you did here. Skimmer with a recirculating co2 scrubber, large refugium opposite my lights, and I know have a 55 gallon tank full of kalk dripping as much as I can to match evaporation.

I am not overly concerned with it, but my ph is not stable like yours. Around a .26 daily difference.
 

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It is not a true statement. Stony Coral growth is directly impacted by what number the ph is. This is more fact than theory at this point. You are the one missing this.
We are going in circles... You are trying to measure a level of precision with a tool that is not capable of returning your desired precision.
 
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I have not been rude at all and apologize if you feel that I have been.

Accuracy is +/- .1 percent.

That means of the REAL pH of the sample is 8.1 than the PROBE is capable of returning a value of somewhere between 8.0 and 8.2

That is the PROBE it outputs a voltage to the p4. The p4 takes that voltage and turns it into a digital number between 0 and 1023. That number is filtered and then rounded to a single decimal place. There is no documentation as to how the software does this or if a value of 8.15 or 7.549 is rounded up or down, etc.

These are hobby intruments, not lab equipment where all of this would be clearly documented as accuracy, error and precision. (all different qualities of the returned number).
Yes I am aware a .1 accuracy can mean 8.0-8.2, which I have alluded to earlier. It is the rounding that I disagreed with. If they do round then it is not a truthful claim in my opinion. But there is nothing saying they do. Not saying they don’t, but you can’t say they do without the asterisk that it is not known.
 
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We are going in circles... You are trying to measure a level of precision with a tool that is not capable of returning your desired precision.
I have said multiple times that I do not believe one of my probes is reading within the margins the manufacture states. And I want to figure out which one is more right so I have some clue of what my number is. The manufacturer claims a .1 accuracy, I am not trying to get better than their claim!
 

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Yes I am aware a .1 accuracy can mean 8.0-8.2, which I have alluded to earlier. It is the rounding that I disagreed with. If they do round then it is not a truthful claim in my opinion. But there is nothing saying they do. Not saying they don’t, but you can’t say they do without the asterisk that it is not known.

I just explained that there is most certainly rounding. The probe returns an analog voltage (or current) turned into a voltage). It is read by a 10 it ADC (Analog to Digital Converter) that turns it into a number from between 0 and 1024. The resulting number is turned into a pH with a single decimal point.
 
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I just explained that there is most certainly rounding. The probe returns an analog voltage (or current) turned into a voltage). It is read by a 10 it ADC (Analog to Digital Converter) that turns it into a number from between 0 and 1024. The resulting number is turned into a pH with a single decimal point.
It is certainly not rounded from .2 to .1 as you have claimed without their .1 claim being a lie.
 

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I have said multiple times that I do not believe one of my probes is reading within the margins the manufacture states. And I want to figure out which one is more right so I have some clue of what my number is. The manufacturer claims a .1 accuracy, I am not trying to get better than their claim!
IT IS NOT .1 ACCURACY

IT IS +/- .1

1675883669130.png


And actually that is just an estimation that is ROUNDED. The probe reads a voltage/current and accuracy is measure in millivolts offset at exactly 25C.

I this case (from what I read) is
25 degree C > 95% of the theoretical value (of the slope) and zero offset < 20 mV

any temperature outside of exactly 25C has to be compensated for and is not linear, but more estimation or "rounding".


Goodness this is getting silly.
 

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You need a better instrument to decipher this. What buffers are you using currently?
i highly recommend an Oakton Ph 5+ (they are like $400) it uses 5 point calibration and auto recognizes most buffers.
it will work for your testing parameters.

we use them at work and they are always very close to the numbers we get when we bring it back to the lab and use Hatch and Mettler Toledo benchtop units that are much more expensive.



a
 
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IT IS NOT .1 ACCURACY

IT IS +/- .1

1675883669130.png


And actually that is just an estimation that is ROUNDED. The probe reads a voltage/current and accuracy is measure in millivolts offset at exactly 25C.

I this case (from what I read) is
25 degree C > 95% of the theoretical value (of the slope) and zero offset < 20 mV

any temperature outside of exactly 25C has to be compensated for and is not linear, but more estimation or "rounding".


Goodness this is getting silly.
Dude +\-.1 has absolutely nothing to do with rounding from .2 to .1. NOTHING

And my tank temp is max 1 degree off from 25 which is compensated through the temp probe. There is no way a 1 degree temp change that is compensated has any effect large enough to what you claim. It is not rounded from .2 to .1, end of story. If the accuracy is really .1. Oh I’m sorry, +\-.1, they are not rounding from .2 to .1 because of a 1 defree temperature change that is compensated for.

What is the change in measured accuracy for ph from 25 to 26 degrees?
 

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It is certainly not rounded from .2 to .1 as you have claimed without their .1 claim being a lie.


Dude +\-.1 has absolutely nothing to do with rounding from .2 to .1. NOTHING

You are misinterpreting what was said and unfortunately I have not been able to explain to you why. I have tried to help you to understand that level of precision that you seek cannot be offered by the devices that you are using. It is really that simple.
 
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You are misinterpreting what was said and unfortunately I have not been able to explain to you why. I have tried to help you to understand that level of precision that seek cannot be offered by the devices that you are using. It is really that simple.
The problem obviously is that the OP insists on believing manufacturers marketing hype where they make claims that are ambiguously worded to impress hobbiest level buyers.

He should just go out and buy a $3-5k lab instrument from a scientific supplier, which does what he thinks he needs.
 
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The problem obviously is that the OP insists on believing manufacturers marketing hype where they make claims that are ambiguously worded to impress hobbiest level buyers.

He should just go out and buy a $3-5k lab instrument from a scientific supplier, which does what he thinks he needs.
No I am not. This entire thread is on my ph probes not reading to what they claim and I have other threads where I threw probes in the trash because they were garbage. This entire useless argument is based on this strange notion that 1 degree of compensated temperature causes enough of an error combined with rounding of the ph probe at a claimed accuracy of .1 to mean the GHL accuracy claim of .1 really means .2 because of rounding.
 
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No I am not. This entire thread is on my ph probes not reading to what they claim and I have other threads where I threw probes in the trash because they were garbage. This entire useless argument is based on this strange notion that 1 degree of compensated temperature causes enough of an error combined with rounding of the ph probe at a claimed accuracy of .1 to mean the GHL accuracy claim of .1 really means .2 because of rounding.
If we are going to talk about wether these probes are as accurate as they claim, fine talk about that. That is not what has been discussed.
 
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You are misinterpreting what was said and unfortunately I have not been able to explain to you why. I have tried to help you to understand that level of precision that you seek cannot be offered by the devices that you are using. It is really that simple.
I know exactly what you are saying, make no mistake. I think you are wrong.
 

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