PH Meter value question

[Bubbles2]

New PH meter, Dr. Beverage testing it in Hanna Sachets 7.01 and 4.01
https://www.amazon.com/dp/B00ST3VTQ4/ref=nav_timeline_asin?_encoding=UTF8&psc=1

What is .14 equate to, when the meter is supposed to be accurate .02 + or -

I guess my question is the scale the meter uses to roll over to a whole number.
6.87 + .14 = 7.01 Meaning that it is not 100's to roll the .87. The .87 rolls to 7 at + .13 meaning this meter is off .14 ? 6.87 + .14 ='s 7.01 ?

I measured my Hanna 7.01 sachet and it calibrates to 6.87
I measured my Hanna 4.01 Sachet and it calibrates to 4.00
Storage solution read 3.34

I bought the Dr Bev after buying an Apera meter which is not as sensitive.
Dr Beverage is supposed to be .02 + or -
Apera is supposed to be .1 + or -


https://www.amazon.com/Apera-Instru...=2025&creative=165953&creativeASIN=B01ENFOHN8
Apera Meter test / same sachets
4.1 in 4.01 sachet
7.1 in 7.01 sachet
Storage solution read 3.4

 

[Oginme]

The Dr Beverage pH meter you have linked to has automatic calibration point of 6.86 pH. If you calibrate it to a 7.01 buffer, you are purposely skewing the pH meter readings, which makes the accuracy of the pH meter immaterial by having the pH meter read a 7.01 buffer as 6.86. You can calibrate to a 6.86 buffer solution and then check it in a 7.01 buffer to test accuracy, but you cannot calibrate it with the 7.01 buffer.

 

[Bubbles2]

The Dr Beverage pH meter you have linked to has automatic calibration point of 6.86 pH. If you calibrate it to a 7.01 buffer, you are purposely skewing the pH meter readings, which makes the accuracy of the pH meter immaterial by having the pH meter read a 7.01 buffer as 6.86. You can calibrate to a 6.86 buffer solution and then check it in a 7.01 buffer to test accuracy, but you cannot calibrate it with the 7.01 buffer.

I did the same thing with the name. I made the mistake of calling Dr Bev but it is Dr Meter as is the Link. I went through the same thing with Dr Bev from another Vendor where he was insistant on knowing about Ph meters but sent me 7.01 sachet to calibrate. Which after having both in my hands the only difference appears to be the battery type used and color between Dr Meter and Dr Beverage.

So the .12 points was OFF .12 points OFF due to calibration....

They sent packets of Buffer but it calls for De ionized H20 which is ridiculous to find local and to have shipped is ridiculous too. I see some used Distilled but that is indeed different than Dionized.

 

[Oginme]

You can use distilled water for making down the buffer solutions.

 

[Bubbles2]

You can use distilled water for making down the buffer solutions.

Is that what you use to mix those dry packets? The packaged does not state either only De ionized

 

[day_trippr]

RODI water is so close to distilled the difference is likely inconsequential in this usage...

Cheers!

 

[Bubbles2]

So after Oginme enlightened me about the calibration set values or auto values. I was reading about if wanting to read outside of the scope of calibration it is not reliable.
A meter calibrated down to 4.01 is not worth much trying to read something that is 3.5... Ya'll just 'pop' for the expensive meters that have more Cal points? I found Hanna has one for wine but the last two Hannas I had were not that good when I was using them for Hydroponic growing.

 

[bracconiere]

ph is logarithmic...base 10...

 

[Oginme]

So after Oginme enlightened me about the calibration set values or auto values. I was reading about if wanting to read outside of the scope of calibration it is not reliable.
A meter calibrated down to 4.01 is not worth much trying to read something that is 3.5... Ya'll just 'pop' for the expensive meters that have more Cal points? I found Hanna has one for wine but the last two Hannas I had were not that good when I was using them for Hydroponic growing.

A meter calibrated between 4.01 and 6.86 will work fine for a reasonable range around those values. The issue comes with calibration of a pH meter calibrated at 4.01 and 6.86 and trying to get an accurate measurement at pH readings above 9. As bracconiere pointed out, the reading given as pH is logarithmic and is very reliably modeled over a short range with two point calibration. A three point calibration will enable readings through the entire range of measurable pH from 1 to 11 to be reasonably accurate.

 

[dmtaylor]

A meter calibrated between 4.01 and 6.86 will work fine for a reasonable range around those values. The issue comes with calibration of a pH meter calibrated at 4.01 and 6.86 and trying to get an accurate measurement at pH readings above 9. As bracconiere pointed out, the reading given as pH is logarithmic and is very reliably modeled over a short range with two point calibration. A three point calibration will enable readings through the entire range of measurable pH from 1 to 11 to be reasonably accurate.

I agree. My further thoughts:

Extrapolation is no big deal, within reason. Even interpolation ain't perfect. However the greatest source of error in any measurement by homebrewer-garage-scientists is... that we are homebrewer-garage-scientists!! Being that I have a bachelor's degree in chemical engineering, I like to think I know how to calibrate and measure properly. However I know I can't say the same for millions of other homebrewers. Consider whether if you don't really know what you're doing or why, whether you are probably just wasting your time and effort entirely with attempts to anal-retentively measure anything quantitatively (NOT directed at you Oginme personally, but just in general terms).

 

[ScrewyBrewer]

@Bubbles2 the Hanna pH meter I have can be configured to automatically calibrate using either of two sets of standard buffers (pH 4.01 / 7.01 / 10.01 or pH 4.01 / 6.86 / 9.18). Though I've always used the 4.01, 7.01 and 10.01 pH solutions for calibration.

For better pH measurement accuracy calibrate your meter using buffer solutions that bracket the pH of the sample to be measured. For measuring wort pH calibrate the meter using the 4.01 and 7.01 buffers. Also calibrate your meter using buffer solutions at or near your wort sampling temperature. For instance I like to calibrate my pH meter and measure wort samples at 77F.

 

[eric19312]

That seems like a nice meter for the price. Good instructions for use of pH meters can be found in this thread: https://www.homebrewtalk.com/forum/threads/ph-meter-calibration.302256/

I'd be interested in the results of a stability test (described in point 11b on first post of the thread) if you decide to do one. 0.01 resolution is only helpful if meter is calibrated and stable.

 

[Oginme]

I agree. My further thoughts:

Extrapolation is no big deal, within reason. Even interpolation ain't perfect. However the greatest source of error in any measurement by homebrewer-garage-scientists is... that we are homebrewer-garage-scientists!! Being that I have a bachelor's degree in chemical engineering, I like to think I know how to calibrate and measure properly. However I know I can't say the same for millions of other homebrewers. Consider whether if you don't really know what you're doing or why, whether you are probably just wasting your time and effort entirely with attempts to anal-retentively measure anything quantitatively (NOT directed at you Oginme personally, but just in general terms).

As a fellow ChemE, I agree with a lot of what you stated above. I was going to say something similar, but decided I could not word it appropriately. I work on research and development, where we have very fancy (read expensive) and accurate pH meters which need constant attention to maintain the accuracy we need for some synthesis steps. Some homebrewers get excited over being off by a few 100ths of a unit and need to think about how much of a difference it really means to their end product. If I am within a tenth of my mash pH prediction I consider it great; within the optimal activity range for enzyme activity as satisfactory. I do tend to over measure things, but keeping that in mind, I don't try to control everything to the nth degree when it is within normal variation for the materials and process I employ.

 

[Bubbles2]

Thank you all for your input. I agree with everything and the real question (which I may have not stated well) would be:
If the meter is calibrated 4.00 6.86 and 9.1 for instance, I was under the impression that the meter would not give a reliable reading say at 3.5 where I use this for wine too. I thought the slope referred to that, where it seems that it refers to temp?
Never the less, I am wondering if the meter is close enough to read 3.5 .5 beyond calibration?

.5 is quite a bit be it beer or wine... even 1-2 with wine is quite a bit when considering storing for a year or two.

Hanna makes a wine meter that is 3.00 to 7.00 for 120.00 + ship.
I'd like to know if it is needed to get a true 3.5 reading or will one of these $30-$60 4.01 calibrated ones read it reliable?
Like the storage solution measurement above in the first post, measured 3.5, is that what storage solution from BioPharm is ? or is it 3.00 and that is all the two meters could pick up?

 

[bracconiere]

as far as i know, 4.01-7 calibration will read all the way down to 0

but i doubt a $30 ph meter would be very good....

 

[Bubbles2]

as far as i know, 4.01-7 calibration will read all the way down to 0

but i doubt a $30 ph meter would be very good....

Chinese slave labor makes thing more and more affordable. I have both here. Once a $100. meter and the other a $45 dollar meter now being sold for $60 and $30 respectively. Yet a 350.00 meter still needs all the babysitting as these cheap ones with the caviet of being able to clean the glass probe if it gets clogged. Like the 120 Hanna mentioned, comes with cleaning solution. (Prob HCL diluted)

 

[bracconiere]

I used a automatic calibrating one for the 4 months it lasted...then it wouldn't calibrate, so i got a manual calibration Milwaukee MW-101...been using it for 10 years, still pretty accurate....at least enough to brew beer, and make sure one of my mad scientist experiments won't kill me....

but back on topic, @Oginme should be able to confirm, you can test a 3.5 solution with a two point 4.01-7 cal.....(i think, or let me know if i've been doing it wrong anyway, i test stuff down to 0 with a 4.01-7 cal)

 

[Cato1507]

I have an Apera ph meter. I think it was $79, and it's quite good IMO. I've used benchtops in labs that were harder to calibrate and use.
It also has a replaceable probe.

 

[Bubbles2]

I used a automatic calibrating one for the 4 months it lasted...then it wouldn't calibrate, so i got a manual calibration Milwaukee MW-101...been using it for 10 years, still pretty accurate....at least enough to brew beer, and make sure one of my mad scientist experiments won't kill me....

but back on topic, @Oginme should be able to confirm, you can test a 3.5 solution with a two point 4.01-7 cal.....(i think, or let me know if i've been doing it wrong anyway, i test stuff down to 0 with a 4.01-7 cal)

I did not see your meter is manual?

 

[Bubbles2]

FWIW. Apera the one that is accurate to .1 told me on the phone that the unit is good for 2 points either way on the calibration. So 4 is good to 2 and 7 to 9. The accuracy could be if reading 3.5 might me 3.4 or 3.6 with that degree of accuracy on such a cheap unit. Thanks for the input and it looks like I learned something.

 

[bracconiere]

lol, being that i'm hanging out in a thread with a couple chemical engineers...and this is only slighthly off-topic, still ph related, but is it possible to have a acid-base salt, that is a liquid? i'm asking for a friend.....

FWIW. Apera the one that is accurate to .1 told me on the phone that the unit is good for 2 points either way on the calibration. So 4 is good to 2 and 7 to 9. The accuracy could be if reading 3.5 might me 3.4 or 3.6 with that degree of accuracy on such a cheap unit. Thanks for the input and it looks like I learned something.

so is the case closed?

 

[Oginme]

If the meter is calibrated 4.00 6.86 and 9.1 for instance, I was under the impression that the meter would not give a reliable reading say at 3.5 where I use this for wine too. I thought the slope referred to that, where it seems that it refers to temp?
Never the less, I am wondering if the meter is close enough to read 3.5 .5 beyond calibration?

We define the pH as the -log[H+] (negative log of the concentration of hydrogen ions in solution) in order to make the relationship linear. So to do a proper calibration, you need at least two points to set the slope and intercept of the readings in order to get a correct reading. Three points are more desirable if you are taking readings over a wide range of pH in order to ensure the exact slope over that range.

 

[Oginme]

lol, being that i'm hanging out in a thread with a couple chemical engineers...and this is only slighthly off-topic, still ph related, but is it possible to have a acid-base salt, that is a liquid? i'm asking for a friend.....

All water soluble salts are a combination of an acid and a base. When they dissolve in water, they come apart to form a cation (acidic) and an anion (basic). The strength of the two ions determines how the salt will change the pH of the solution. A strong cation with a weak base will cause the pH to decrease and a strong anion with a weak cation will cause the pH to rise.

 

[bracconiere]

All water soluble salts

lol, this crap won't even dissolve in a 5 gal bucket of water....for the record i'm playing around with esters created while brewing....

thank you for the reply! you've given me something to go on....(note to self, learn more about cations, and anions, )

edit: it is lipiphilic though....

 

[day_trippr]

fwiw, Apera makes numerous pH meters. I suspect the OP is referring to one of their "value" line products, specifically the pH20 model, which does indeed sport 0.1 resolution & accuracy specs.

Meanwhile their "premium" line pH60 model that has been popular with HBT is spec'd to 0.01 resolution & accuracy. I have one of these and am quite happy with it...

Cheers!

 

[eric19312]

fwiw, Apera makes numerous pH meters. I suspect the OP is referring to one of their "value" line products, specifically the pH20 model, which does indeed sport 0.1 resolution & accuracy specs.

Meanwhile their "premium" line pH60 model that has been popular with HBT is spec'd to 0.01 resolution & accuracy. I have one of these and am quite happy with it...

Cheers!

I have the same Apera...it is my second meter replacing my old Hanna pHep®5. I'm really happy with the Apera. That Hanna cup would never keep the probe from drying out and the battery lid was also a recurring nightmare. I did confirm the Apera's stability with the test AJ recommended and got a good result.