What ph number to believe

BeanAnimal

Valuable Member
Review score
+0 /0 /-0
View Badges
Joined
Jul 16, 2009
Messages
1,053
Reaction score
1,164
Review score
+0 /0 /-0
Rating - 0%
0   0   0
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.
 
OP
Lionfish hunter

Lionfish hunter

Well-Known Member
Review score
+0 /0 /-0
View Badges
Joined
Jan 18, 2021
Messages
997
Reaction score
634
Review score
+0 /0 /-0
Location
Houston
Rating - 0%
0   0   0
.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

2500 Club Member
Review score
+0 /0 /-0
View Badges
Joined
Mar 2, 2016
Messages
2,533
Reaction score
1,764
Review score
+0 /0 /-0
Location
Potomac
Rating - 0%
0   0   0
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...


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...
 
Top Shelf Aquatics

BeanAnimal

Valuable Member
Review score
+0 /0 /-0
View Badges
Joined
Jul 16, 2009
Messages
1,053
Reaction score
1,164
Review score
+0 /0 /-0
Rating - 0%
0   0   0
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.
 
OP
Lionfish hunter

Lionfish hunter

Well-Known Member
Review score
+0 /0 /-0
View Badges
Joined
Jan 18, 2021
Messages
997
Reaction score
634
Review score
+0 /0 /-0
Location
Houston
Rating - 0%
0   0   0
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.
 
OP
Lionfish hunter

Lionfish hunter

Well-Known Member
Review score
+0 /0 /-0
View Badges
Joined
Jan 18, 2021
Messages
997
Reaction score
634
Review score
+0 /0 /-0
Location
Houston
Rating - 0%
0   0   0
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.
 
www.dinkinsaquaticgardens.com
OP
Lionfish hunter

Lionfish hunter

Well-Known Member
Review score
+0 /0 /-0
View Badges
Joined
Jan 18, 2021
Messages
997
Reaction score
634
Review score
+0 /0 /-0
Location
Houston
Rating - 0%
0   0   0
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

Valuable Member
Review score
+0 /0 /-0
View Badges
Joined
Jul 16, 2009
Messages
1,053
Reaction score
1,164
Review score
+0 /0 /-0
Rating - 0%
0   0   0
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.
 
OP
Lionfish hunter

Lionfish hunter

Well-Known Member
Review score
+0 /0 /-0
View Badges
Joined
Jan 18, 2021
Messages
997
Reaction score
634
Review score
+0 /0 /-0
Location
Houston
Rating - 0%
0   0   0
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.
 
Reef Chasers Aquaculture

BeanAnimal

Valuable Member
Review score
+0 /0 /-0
View Badges
Joined
Jul 16, 2009
Messages
1,053
Reaction score
1,164
Review score
+0 /0 /-0
Rating - 0%
0   0   0
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!
 
Top Shelf Aquatics

Randy Holmes-Farley

Reef Chemist
Review score
+0 /0 /-0
View Badges
Joined
Sep 5, 2014
Messages
59,051
Reaction score
53,091
Review score
+0 /0 /-0
Location
Arlington, Massachusetts, United States
Rating - 0%
0   0   0
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.
 
OP
Lionfish hunter

Lionfish hunter

Well-Known Member
Review score
+0 /0 /-0
View Badges
Joined
Jan 18, 2021
Messages
997
Reaction score
634
Review score
+0 /0 /-0
Location
Houston
Rating - 0%
0   0   0
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.
 
Coral Mania Live Sale
OP
Lionfish hunter

Lionfish hunter

Well-Known Member
Review score
+0 /0 /-0
View Badges
Joined
Jan 18, 2021
Messages
997
Reaction score
634
Review score
+0 /0 /-0
Location
Houston
Rating - 0%
0   0   0
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.
 

Randy Holmes-Farley

Reef Chemist
Review score
+0 /0 /-0
View Badges
Joined
Sep 5, 2014
Messages
59,051
Reaction score
53,091
Review score
+0 /0 /-0
Location
Arlington, Massachusetts, United States
Rating - 0%
0   0   0
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!
 
Tidal Gardens

arking_mark

2500 Club Member
Review score
+0 /0 /-0
View Badges
Joined
Mar 2, 2016
Messages
2,533
Reaction score
1,764
Review score
+0 /0 /-0
Location
Potomac
Rating - 0%
0   0   0
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...


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?
 
Back
Top