What ph number to believe

[BeanAnimal]

I will also repeat again

These are hobby toys, not lab equipment or lab workflows.

The probe is only part of the equation. The data filtering, noise compensation, ad converter and a dozen other things differentiate a Profilux from a lab instrument.

You also have temperature compensation to deal with... and that itself has error that compounds the actual pH reading error.

Pick one of them and use it... stability and ballpark is more important than 1 or 2 tenths of a pH.

 

[Lionfish hunter]

.1 accuracy

REAL pH 8.2

Reading 1 8.1
Reading 2 8.3

Highly unlikely they are both reading exactly.1 off on the extreme ends to make this scenario true. Which is why I said I am not confident one of them is not reading more than .1 off. I also had to change calibration fluids and calibrate both of them many times to achieve the .2 difference. Either my 9 or 10 ph fluid is off already. My next plan is to order new 7, 9, and 10 fluids. Calibrate both probes and temp sensors to the 7 and 10 fluid. Then check with the 9 after on both probes. See which one is off at ph of 9.

 

[arking_mark]

I have never had a problem with drifting precision nor have I claimed to. My concern is accuracy and have never said anything else.

The issue is that these pH measurement devices aren't all that accurate and go out of calibration fairly quickly. Given any 2 devices with +/-0.2 an actual 8.2pH could read 8.0 or 8.4 and they are both "right" within their accuracy.

As mentioned before. A great was to assess your pH probe measurement is...

A simple way to assess your pH measurements

A couple of facts: There is a mathematical model for pH, Alk, and CO2. Given any two of these you can calculate the 3rd. Most pH meters and test kits have an accuracy of +/- 0.2. A pH measurement below 7.8 is most likely a measurement error (or 7.6 due to the accuracy of your meter or test kit)...

www.reef2reef.com

You're Alk measurements of 8.5dKH with a +/- 0.5 accuracy would put your outdoor aerated cup of water between 8.27 and 8.31 NBS.

Go aerate a cup of water and measure its pH to see which probe is working best...

 

[BeanAnimal]

Highly unlikely they are both reading exactly.1 off on the extreme ends to make this scenario true. Which is why I said I am not confident one of them is not reading more than .1 off. I also had to change calibration fluids and calibrate both of them many times to achieve the .2 difference. Either my 9 or 10 ph fluid is off already. My next plan is to order new 7, 9, and 10 fluids. Calibrate both probes and temp sensors to the 7 and 10 fluid. Then check with the 9 after on both probes. See which one is off at ph of 9.

You make no sense. They don't need to be exactly .1 off for those readings to occur. Back to resolution... the .1 is rounded but not part of the accuracy... you said you understood that, but do not appear to.

You are free to throw as much money as this as you wish. But with this grade of equipment, these are the expected results.

More importantly you are chasing precision that just doesn't matter to anything but you. The tank doesn't care for sure.

 

[Lionfish hunter]

I will also repeat again

These are hobby toys, not lab equipment or lab workflows.

The probe is only part of the equation. The data filtering, noise compensation, ad converter and a dozen other things differentiate a Profilux from a lab instrument.

Pick one of them and use it... stability and ballpark is more important than 1 or 2 tenths of a pH.

Ghl specifically states it is a high quality lab grade sensor. I am not changing my ph all at once and my ph stability is not of concern. I am concerned about getting high ph. Wether you believe a high ph gives significant coral growth gains is up to you. I am confident it does and am concerned with the actual number.

 

[Lionfish hunter]

You make no sense. They don't need to be exactly .1 off for those readings to occur. Back to resolution... the .1 is rounded but not part of the accuracy... you said you understood that, but do not appear to.

You are free to throw as much money as this as you wish. But with this grade of equipment, these are the expected results.

Please show me where GHL says their .1 accuracy claim is rounded down from .2.

 

[Lionfish hunter]

You make no sense. They don't need to be exactly .1 off for those readings to occur. Back to resolution... the .1 is rounded but not part of the accuracy... you said you understood that, but do not appear to.

You are free to throw as much money as this as you wish. But with this grade of equipment, these are the expected results.

More importantly you are chasing precision that just doesn't matter to anything but you. The tank doesn't care for sure.

When you have pieces of coral that worth 600$ a half inch. It can be worth the money to ensure you have a high ph if that means twice the growth.

 

[BeanAnimal]

Please show me where GHL says their .1 accuracy claim is rounded down from .2.

I suggest actually reading a bit about resolution, accuracy and significant digits this conversation makes no sense without your understanding of that and if you understood that, we would not be having the conversation

I wish you luck - but I can't help you further.

 

[Lionfish hunter]

I suggest actually reading a bit about resolution, accuracy and significant digits this conversation makes no sense without your understanding of that and if you understood that, we would not be having the conversation

I wish you luck - but I can't help you further.

.1 does not mean .2, good luck.

 

[BeanAnimal]

When you have pieces of coral that worth 600$ a half inch. It can be worth the money to ensure you have a high ph if that means twice the growth.

Playing devils advocate here:

Lets say you had a probe that DID give PERFECT pH readings down to .01 or .001

Knowing that pH swings with NUMEROUS variables in your aquarium by the minute/day/hour even in the most stable system... what do you suggest is done with that perfect number?

In that context - if you have piles of $1200/in coral - wouldn't you be investing thousands in REAL LAB grade equipment to protect that investment or business.

Happy Reefing!

 

[BeanAnimal]

.1 does not mean .2, good luck.

I suggest actually reading a bit about resolution, accuracy and significant digits.

 

[Lionfish hunter]

I suggest actually reading a bit about resolution, accuracy and significant digits.

Yeah I went to college. Please explain how a claimed accuracy of .1 means .2.

 

[BeanAnimal]

Yeah I went to college. Please explain how a claimed accuracy of .1 means .2.

I suggest actually reading a bit about resolution, accuracy and significant digits.

 

[Randy Holmes-Farley]

OK, let's all relax a bit.

FWIW, if something claims +/- 0.1 accuracy, then two of them can deviate by 0.2 without necessarily being outside of the limits.

 

[Lionfish hunter]

OK, let's all relax a bit.

FWIW, if something claims +/- 0.1 accuracy, then two of them can deviate by 0.2 without necessarily being outside of the limits.

Yes I understand that. But bean animal is saying that if GHL claims .1 accuracy, they are rounding and they actually mean .2.

 

[Lionfish hunter]

Yes I understand that. But bean animal is saying that if GHL claims .1 accuracy, they are rounding and they actually mean .2.

Which is wrong, no matter how many times you say read about resolution, accuracy, and significant digits.

 

[BeanAnimal]

OK, let's all relax a bit.

FWIW, if something claims +/- 0.1 accuracy, then two of them can deviate by 0.2 without necessarily being outside of the limits.

We keep trying to explain that Randy

 

[Randy Holmes-Farley]

Yes I understand that. But bean animal is saying that if GHL claims .1 accuracy, they are rounding and they actually mean .2.

OK, let's all just move one from that discussion.

I agree that ph is very frustrating!

 

[Lionfish hunter]

We keep trying to explain that Randy

This is not what you were saying!

 

[arking_mark]

The issue is that these pH measurement devices aren't all that accurate and go out of calibration fairly quickly. Given any 2 devices with +/-0.2 an actual 8.2pH could read 8.0 or 8.4 and they are both "right" within their accuracy.

As mentioned before. A great was to assess your pH probe measurement is...

A simple way to assess your pH measurements

A couple of facts: There is a mathematical model for pH, Alk, and CO2. Given any two of these you can calculate the 3rd. Most pH meters and test kits have an accuracy of +/- 0.2. A pH measurement below 7.8 is most likely a measurement error (or 7.6 due to the accuracy of your meter or test kit)...

www.reef2reef.com

You're Alk measurements of 8.5dKH with a +/- 0.5 accuracy would put your outdoor aerated cup of water between 8.27 and 8.31 NBS.

Go aerate a cup of water and measure its pH to see which probe is working best...

Did you try this? Did either probe get close?