What ph number to believe

[Steve2020]

Repeatability is of course important. But repeatability of wrong numbers is not helpful.

Apparently I just had a 3 hour argument with a guy about how I thought he was wrong about these probes having a -+.2 acceptable range when that wasn’t even his opinion.

So yeah repeatability of +-.1 is important and will work just fine.

If you don't mind me asking, what PH range on the high end and what kind of swing from day to night are you wanting to achieve?

 

[Lionfish hunter]

I have actually stated numerous times that you are misstating and/or not understanding what I (and others) are trying to explain to you.

Several people here have attempted numerous times to help you understand what +/- .1 accuracy means in context to what your instrument displays and how that reading compares to the actual pH.

Try this:

If we take TWO +/- .1 pH probes that are guaranteed to be +/- .1 ph Unit of the actual fluid.

You measure a sample with YOUR probe and it reads 8.1
the actual value could be 8.0, 8.1 or 8.2
The range from 8.0 to 8.2 is .2
You don't know what value is correct, it could be anywhere between 8.0 and 8.2

I come to your house and put my +/- .1 probe in your tank.
my probe reads 8.2
the actual value could be: 8.1, 8.2 or 8.3
The range from 8.1 to 8.3 is .2
I don't know what value is correct, it could be anywhere between 8.1 and 8.4


IMPORTANT:
You can't see my probe reading and I can't see your probe reading. But both probes are accurate to +/- .1
Which reading is correct and which probe is correct. We know have values between 8.0 and 8.4!

Are you beginning to see the problem?

Now if you and I compare values, we can see that the (if both probes are accurate) then the real pH is likely 8.1 or 8.2

Great, if we already know both probes are accurate. But if we don't then we are back to where we started.

No you keep trying to give me basic lessons on accuracy instead of actually saying I misunderstood you on the entire premise of the argument. Which you just did again! Go back in my arguments and find one time where I screwed up the meaning of accuracy. -+.1 means .1 on either end yes, why do you keep telling me this!

 

[Lionfish hunter]

If you don't mind me asking, what PH range on the high end and what kind of swing from day to night are you wanting to achieve?

I am not worried about day night swings. I do keep my refugium opposite of my tank lights. Average ph of 8.3-8.4 is what I try for.

 

[YOYOYOReefer]

one thing you could do is find something in your house to use as a baseline to test your probes/ buffer fluids.
i use extra virgin olive oil , the brand we buy in gallon jugs is very consistant (have been using it 10+ years) and we cook with it so its always here... you could use vinegar etc.

 

[Lionfish hunter]

I have actually stated numerous times that you are misstating and/or not understanding what I (and others) are trying to explain to you.

Several people here have attempted numerous times to help you understand what +/- .1 accuracy means in context to what your instrument displays and how that reading compares to the actual pH.

Try this:

If we take TWO +/- .1 pH probes that are guaranteed to be +/- .1 ph Unit of the actual fluid.

You measure a sample with YOUR probe and it reads 8.1
the actual value could be 8.0, 8.1 or 8.2
The range from 8.0 to 8.2 is .2
You don't know what value is correct, it could be anywhere between 8.0 and 8.2

I come to your house and measure the same sample with my +/- .1 probe.
my probe reads 8.2
the actual value could be: 8.1, 8.2 or 8.3
The range from 8.1 to 8.3 is .2
I don't know what value is correct, it could be anywhere between 8.1 and 8.4

Both probes are reading within their specified accuracy.


IMPORTANT:
You can't see my probe reading and I can't see your probe reading. But both probes are accurate to +/- .1
Which reading is correct and which probe is correct? We know have values between 8.0 and 8.4! I am sure that value is between 8.1 and 8.3 but you are sure the value is between 8.0 and 8.2

Are you beginning to see the problem?

Now if you and I compare values, we can see that the (if both probes are accurate) then the real pH is likely 8.1 or 8.2

Great, if we already know both probes are accurate. But if we don't then we are back to where we started.

That is - if your probe IS accurate, it is telling you within .2, not .1 what the pH is.

Randy Holmes-Farley said:
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.

this above is an old post btw

 

[Lionfish hunter]

I just posted a post of mine many posts back where I agree with Randy and that I agree with him on what accuracy means.

 

[Lionfish hunter]

And it would have been nice if you would have told me then that I misunderstood you on the whole accuracy of GHL to .2

 

[Lionfish hunter]

one thing you could do is find something in your house to use as a baseline to test your probes/ buffer fluids.
i use extra virgin olive oil , the brand we buy in gallon jugs is very consistant (have been using it 10+ years) and we cook with it so its always here... you could use vinegar etc.

Thank you for giving constructive advice after a fairly heated argument. I appreciate that.

 

[BeanAnimal]

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

this above is an old post btw

That is not what was said.

 

[Lionfish hunter]

That is not what was said.

Yes I misunderstood what you said with what somebody else said. Then we argued about it for hours.

 

[Steve2020]

This has not been my luck with GHL probes...of course there could be electrical interference or something making my experience suboptimal.

I have never had any issues with the PH probes. Mine have hit their 2yr point and still reading fine. I clean and calibrate every 3-4wks whether they need it or not. I have spares that I thought I would have already had to install but that has not been the case yet. I Also I learned in the beginning that location and flow, especially flow across the probes is an important factor. Conductivity probes diffidently do not like micro bubbles from the skimmer but I solved that by pointing a small pump towards the probe holder which is fixed to the adjustable weir in my sump.

 

[YOYOYOReefer]

many people struggle with accuracy vs precision .

you were throwing accuracy /precision all over the place.. the difference between accuracy (which in the reef world we dont actually care beyond 1 decimal place,) and precision which means even if your reading of 7 is really 6.9 but you make whaterver ph based adjustments you make from that number of 7 on your device and you repeat it from that baseline your tank will be just fine.

 

[BeanAnimal]

Yes I misunderstood what you said with what somebody else said. Then we argued about it for hours.

Thank you. I have (honestly) been trying to help you wrap your head around all of this. I understand buying a tool and it not meeting an expectation is frustrating. I am not immune to that myself. In fact, I have my own GHL issues right now.

Most of us have been trying to reset your expectation by explaining the limits of the tools that you are using. Once you understand those limitations and can work within them, you will be better off. There are more accurate tools out there, but the general consensus and reality is that the added level of accuracy does not matter. If it does to you, then you may want to invest in one of those tools.

 

[Lionfish hunter]

many people struggle with accuracy vs precision .

you were throwing accuracy /precision all over the place.. the difference between accuracy (which in the reef world we dont actually care beyond 1 decimal place,) and precision which means even if your reading of 7 is really 6.9 but you make whaterver ph based adjustments you make from that number of 7 on your device and you repeat it from that baseline your tank will be just fine.

Can you give an example? Because I know what precision and accuracy mean. It is possible I said one when I ment the other but I do not recall.

 

[Steve2020]

I am not worried about day night swings. I do keep my refugium opposite of my tank lights. Average ph of 8.3-8.4 is what I try for.

If it's not too much to ask could you post a recent 24hr or 48hr chart of your PH?

 

[Lionfish hunter]

If it's not too much to ask could you post a recent 24hr or 48hr chart of your PH?

This is using pin point calibration fluid 7 and 10 for both. Using GHL calibration fluid 7 and 9 with the GHL gave a .1 higher reading. So there is a discrepancy with the calibration fluids being used.

It also took many calibrations with the Neptune to get it correct. It mostly ran .1 to .2 lower than this and then would not read the 7 and 10 calibration fluids correctly so I kept recalibrating until it did.

The GHL has been the most solid for sure. Still reads the calculation fluids the same as the day I calibrated the probe. The Neptune makes me think it is just not accurate.

 

[Steve2020]

This is using pin point calibration fluid 7 and 10 for both. Using GHL calibration fluid 7 and 9 with the GHL gave a .1 higher reading. So there is a discrepancy with the calibration fluids being used.

It also took many calibrations with the Neptune to get it correct. It mostly ran .1 to .2 lower than this and then would not read the 7 and 10 calibration fluids correctly so I kept recalibrating until it did.

The GHL has been the most solid for sure. Still reads the calculation fluids the same as the day I calibrated the probe. The Neptune makes me think it is just not accurate.

Never used Apex but there are MANY threads on issues with the ph probe on numerous sites not reading correctly. Not sure why. As far as the pin point calibration fluid, if using it for the GHL ph probe calibration are you changing the 9 calibration setpoint to 10 in the P4? Just asking. Also if you would like some recommendations on boosting your ph with less swings I could PM you on what I am doing. Never hurts to see what others are doing. I do not use kalkwasser and I disconnected my external refugium in the summer of 2021.

 

[BeanAnimal]

This is using pin point calibration fluid 7 and 10 for both. Using GHL calibration fluid 7 and 9 with the GHL gave a .1 higher reading. So there is a discrepancy with the calibration fluids being used.

It also took many calibrations with the Neptune to get it correct. It mostly ran .1 to .2 lower than this and then would not read the 7 and 10 calibration fluids correctly so I kept recalibrating until it did.

The GHL has been the most solid for sure. Still reads the calculation fluids the same as the day I calibrated the probe. The Neptune makes me think it is just not accurate.

Fluids can become cross contaminated easily with each other or rinse water between readings. In a lab you would never dip the probe into the bottle, but instead pour from the bottle into a calibration vessel.

The fluids also need to be at 25C (or tank temp) depending on the temp compensation of the probe or software.

There is a lot of room for small errors that add up.

 

[Lionfish hunter]

many people struggle with accuracy vs precision .

you were throwing accuracy /precision all over the place.. the difference between accuracy (which in the reef world we dont actually care beyond 1 decimal place,) and precision which means even if your reading of 7 is really 6.9 but you make whaterver ph based adjustments you make from that number of 7 on your device and you repeat it from that baseline your tank will be just fine.

I went though all my posts and could not find one where I used accuracy when I ment precision or the other way around. There was about 20 posting telling me I didn’t know the difference but I am unable to find why. There was some confusion about accuracy of a ph probe vs accuracy of the reading, but that was a misunderstanding. With possibly poor wording on my part vs what I meant.
If you can find where I screwed up the meaning that would be helpful. As I am still confused why I was told so many times what the definition of accuracy means. It isn’t that hard

 

[Lionfish hunter]

Fluids can become cross contaminated easily with each other or rinse water between readings. In a lab you would never dip the probe into the bottle, but instead pour from the bottle into a calibration vessel.

The fluids also need to be at 25C (or tank temp) depending on the temp compensation of the probe or software.

There is a lot of room for small errors that add up.

Yes I ended up using like 8 bags of pin point calibration fluid to not cross contaminate. I started warming the bags up in the aquarium and got so fed up with it I ended up moving the temp probe into the bag for calibration.