I compared my 2 PH meters, with interesting results

[danestead]

Hi guys,

I have 2 digital PH meters:

• Hanna Instruments HI98128 (https://www.hannainst.com.au/product/PHEP5%2528HI98128%2529/pHep%2B5%2BpH%252FTemperature%2BTester%2Bwith%2B001%2BpH%2BResolution)
• ADWA Instruments AD12 (http://www.adwainstruments.com/site/component/content/article/132)

My Hanna is 2 years old (as is the probe) and has a stated accuracy of +-0.05. It cost in the vicinity of $130. I went to buy a new probe for it but discovered that it was half the price to purchase the ADWA, which has a stated accuracy of +-0.01. That meter was $62, delivered to my door.

I thought it would be interesting to compare the reading from the 2 meters with my next brew, which happened to be a week ago. I calibrated both instruments with PH 4 and 7 solutions, then measured the PH 7 solution. The Hanna gave a reading of 7.01 degrees and the ADWA read 7.07. The PH solution was at 15 degrees and the bottle states a PH of 7.04 at that temperature. If my thinking is correct, the Hanna is reading 0.03 low and the ADWA is reading 0.03 high. I thought that was interesting as the ADWA stated accuracy is 0.01 and it is reading outside that. The Hanna is reading within its 0.05 accuracy.

I then started testing the mash of my brew. I added some acid to the mash after each reading. These are the readings I got:

• Hanna 5.60, ADWA 5.78 - then added some acid
• Hanna 5.30, ADWA 5.53 - then added some more acid
• Hanna 5.23, ADWA 5.51

These readings are not really similar at all; and not accurate enough for my brewing purposes. This post is for me to try determine if either of my meters/probes are too old/faulty etc. or if one of these meters are just in general not very good.

My guess/estimation to explain why the PHs were similar when testing the PH calibration solution, but not in the mash, are that I think the calibration solution has a strong ionic power (maybe wrong term for that) however the mash doesn't. The Hanna does take quite some time to settle on a reading (at least a minute whilst moving it around in the cooled mash sample); however the ADWA settles on a reading within about 10 or 15 seconds.

My guess is that my Hanna probe is well over due. I've come to this conclusion based on it struggling to get a stable reading and also because it is 2 years old. I do store it in 'storage solution' however I only brew once a month and by that time, the solution has dried up and is crusty. Could the Hanna reading be that far out after two years?

Thoughts guys?

Edit: My calibration solutions are the 500mL bottle type ones. They seem to last me 6-12ish months. Disposable sachet style solutions would probably be more accurate.

 

[Zorco]

Will follow this with much interest.

 

[Killer Brew]

Hi guys,

I have 2 digital PH meters:

• Hanna Instruments HI98128 (https://www.hannainst.com.au/product/PHEP5%2528HI98128%2529/pHep%2B5%2BpH%252FTemperature%2BTester%2Bwith%2B001%2BpH%2BResolution)
• ADWA Instruments AD12 (http://www.adwainstruments.com/site/component/content/article/132)

My Hanna is 2 years old (as is the probe) and has a stated accuracy of +-0.05. It cost in the vicinity of $130. I went to buy a new probe for it but discovered that it was half the price to purchase the ADWA, which has a stated accuracy of +-0.01. That meter was $62, delivered to my door.

I thought it would be interesting to compare the reading from the 2 meters with my next brew, which happened to be a week ago. I calibrated both instruments with PH 4 and 7 solutions, then measured the PH 7 solution. The Hanna gave a reading of 7.01 degrees and the ADWA read 7.07. The PH solution was at 15 degrees and the bottle states a PH of 7.04 at that temperature. If my thinking is correct, the Hanna is reading 0.03 low and the ADWA is reading 0.03 high. I thought that was interesting as the ADWA stated accuracy is 0.01 and it is reading outside that. The Hanna is reading within its 0.05 accuracy.

I then started testing the mash of my brew. I added some acid to the mash after each reading. These are the readings I got:

• Hanna 5.60, ADWA 5.78 - then added some acid
• Hanna 5.30, ADWA 5.53 - then added some more acid
• Hanna 5.23, ADWA 5.51

These readings are not really similar at all; and not accurate enough for my brewing purposes. This post is for me to try determine if either of my meters/probes are too old/faulty etc. or if one of these meters are just in general not very good.

My guess/estimation to explain why the PHs were similar when testing the PH calibration solution, but not in the mash, are that I think the calibration solution has a strong ionic power (maybe wrong term for that) however the mash doesn't. The Hanna does take quite some time to settle on a reading (at least a minute whilst moving it around in the cooled mash sample); however the ADWA settles on a reading within about 10 or 15 seconds.

My guess is that my Hanna probe is well over due. I've come to this conclusion based on it struggling to get a stable reading and also because it is 2 years old. I do store it in 'storage solution' however I only brew once a month and by that time, the solution has dried up and is crusty. Could the Hanna reading be that far out after two years?

Thoughts guys?

Edit: My calibration solutions are the 500mL bottle type ones. They seem to last me 6-12ish months. Disposable sachet style solutions would probably be more accurate.

I have heard that Hanna have a good support department for working through these types of issues. Might pay to give them a call and see what they suggest also.

 

[MHB]

The slow settling of the Hana is a bit of a worry, but given that both are calibrated in the same solutions my first thought would be that the ATC isn't the same.
ATC is an equation that the onboard software applies to the readings and are often a bit iffy especially near the temperature extremes given for the meter.

The life of pH probes is generally around 12-18 months, perhaps longer if lightly used and stored in storage solution (dried up crust does not count).
I would be very cautious trusting the second decimal on a $68 meter, or on a $168 meter for that matter.

This might be a help https://www.ysi.com/ysi-blog/water-blogged-blog/2013/04/ph-meter-calibration-problems-check-out-these-12-tips
Mark

 

[danestead]

The slow settling of the Hana is a bit of a worry, but given that both are calibrated in the same solutions my first thought would be that the ATC isn't the same.
ATC is an equation that the onboard software applies to the readings and are often a bit iffy especially near the temperature extremes given for the meter.

The life of pH probes is generally around 12-18 months, perhaps longer if lightly used and stored in storage solution (dried up crust does not count).
I would be very cautious trusting the second decimal on a $68 meter, or on a $168 meter for that matter.

This might be a help https://www.ysi.com/ysi-blog/water-blogged-blog/2013/04/ph-meter-calibration-problems-check-out-these-12-tips
Mark

I'll have a look at that link. Thanks Mark.

I've also just read that the probe needs to be hydrated in storage solution for at least 3 hours prior to calibrating; so I'll make sure that is the case next brew, and see if the results change. My crusted up storage solution on the Hanna was definitely not hydrating it prior to calibration!

I too was sceptical on a $62 meter, however I thought at that price, it was worth a shot. The company seem reputable.

 

[TSMill]

I thought ph meters were typically calibrated using 2 data points?

 

[danestead]

I thought ph meters were typically calibrated using 2 data points?

They are. Why do you ask?

 

[trevgale]

I'm also very interested in this. I have the same model Hanna and have never got a consistent reading from it. It is stored in solution, I calibrate it and take a reading of a cooled sample about 15min into the mash. I take a sample later in the mash and it is different by say 0.2, maybe more. What is even more confusing is that if I take a reading of the first sample later on I get a different result that I originally got, even if I re-calibrate.

I guessed it might have been the probe, but for the cost of a replacement I might as well just buy another meter.

What meter are other people using and are you getting a consistent readings throughout the mash?

 

[danestead]

I'm also very interested in this. I have the same model Hanna and have never got a consistent reading from it. It is stored in solution, I calibrate it and take a reading of a cooled sample about 15min into the mash. I take a sample later in the mash and it is different by say 0.2, maybe more. What is even more confusing is that if I take a reading of the first sample later on I get a different result that I originally got, even if I re-calibrate.

I am not the world's best expert on PH meters and brewing science however I do know that the PH of your beer changes during the mash, boil, fermentation etc. Maybe the 0.2 difference you are getting is just the actual mash PH changing. I can't explain why the original sample changed though.

Does this explain what may be happening or do you still suspect your meter is dicky?

This link seems like a fairly in depth explanation on PH during brewing and fermentation.
http://byo.com/malt/item/1494-the-principles-of-ph

Edit: To add more info - I just pulled up some data on the first brew I did with my Hanna 98128. I took heaps of measurements at all different stages of the brewing process. My mash PH went from 5.39 (at start of mash) to 5.43 (at the end of the mash). This is within the 0.05 accuracy of the meter so I'm not really able to say whether the actual PH went up during the mash process or not. It does tend to indicate to me that the PH doesn't change too much during the mash though.

 

[Danscraftbeer]

I've got an AD11. I've put it through the tests enough to feel confident in it. The total trust is left on the calibration fluid itself.
I test my aquaponics water with it too. My rain water tank etc. Tap water, filtered water etc.
As for brews I only test at the beginning of the mash. I checked it at end of mash once I think it was the same.

As for storage though adhere to the instructions. I have a little strip of new chux towel enough to wrap twice around the probe end wet with the PH4 solution.
It stays in the cap and just keeps it moist and humid when capped. The O ring seals it air tight it wont dry out.

 

[TSMill]

They are. Why do you ask?

My bad, misread first post and thought it was just done at 7.

 

[trevgale]

That was an interesting read. I wasn't aware that the meter should only be on when submerged. How much of a pH change should be expected during the mash?

I still think mine is a bit dicky as I have never been able to get consistant readings, even with the same sample.

 

[trevgale]

Hi guys,

I have 2 digital PH meters:

• Hanna Instruments HI98128 (https://www.hannainst.com.au/product/PHEP5%2528HI98128%2529/pHep%2B5%2BpH%252FTemperature%2BTester%2Bwith%2B001%2BpH%2BResolution)
• ADWA Instruments AD12 (http://www.adwainstruments.com/site/component/content/article/132)

My Hanna is 2 years old (as is the probe) and has a stated accuracy of +-0.05. It cost in the vicinity of $130. I went to buy a new probe for it but discovered that it was half the price to purchase the ADWA, which has a stated accuracy of +-0.01. That meter was $62, delivered to my door.

I thought it would be interesting to compare the reading from the 2 meters with my next brew, which happened to be a week ago. I calibrated both instruments with PH 4 and 7 solutions, then measured the PH 7 solution. The Hanna gave a reading of 7.01 degrees and the ADWA read 7.07. The PH solution was at 15 degrees and the bottle states a PH of 7.04 at that temperature. If my thinking is correct, the Hanna is reading 0.03 low and the ADWA is reading 0.03 high. I thought that was interesting as the ADWA stated accuracy is 0.01 and it is reading outside that. The Hanna is reading within its 0.05 accuracy.

I then started testing the mash of my brew. I added some acid to the mash after each reading. These are the readings I got:

• Hanna 5.60, ADWA 5.78 - then added some acid
• Hanna 5.30, ADWA 5.53 - then added some more acid
• Hanna 5.23, ADWA 5.51

These readings are not really similar at all; and not accurate enough for my brewing purposes. This post is for me to try determine if either of my meters/probes are too old/faulty etc. or if one of these meters are just in general not very good.

My guess/estimation to explain why the PHs were similar when testing the PH calibration solution, but not in the mash, are that I think the calibration solution has a strong ionic power (maybe wrong term for that) however the mash doesn't. The Hanna does take quite some time to settle on a reading (at least a minute whilst moving it around in the cooled mash sample); however the ADWA settles on a reading within about 10 or 15 seconds.

My guess is that my Hanna probe is well over due. I've come to this conclusion based on it struggling to get a stable reading and also because it is 2 years old. I do store it in 'storage solution' however I only brew once a month and by that time, the solution has dried up and is crusty. Could the Hanna reading be that far out after two years?

Thoughts guys?

Edit: My calibration solutions are the 500mL bottle type ones. They seem to last me 6-12ish months. Disposable sachet style solutions would probably be more accurate.

Where did you purchase the Adwa meter?

 

[MHB]

I would expect the pH to change, just the amount of CO2 in solution will make a measurable change. As you heat the wort CO2 will come out of solution, reducing the amount of carbonic acid and slightly raising the pH; just sitting on the bench it will take up more CO2 as it cools.
I suspect trying to get accurate and reliable results closer then 0.1 would require a fairly high end pH meter, kept in perfect condition/s and which has the probe changed every year. Research grade and very expensive.
We as home brewers don't I think need anything like that level of precision and are arguably not really getting anything like it - even if the pH meter is telling you you are.
Doesn't mean the $30 ones on eBay will tell you anything useful either, what a friend of mines calls "Prophylactic" (giving one a false sense of security whilst being stuffed).

Mark

 

[danestead]

Where did you purchase the Adwa meter?

http://www.servovendi.com/uk/waterproof-ph-meter-and-temperature-tester-adwa-0-01-ph-ad12.html

 

[danestead]

How much of a pH change should be expected during the mash?

Not really sure. The article didn't really seem to say. MHB may have some idea.

 

[trevgale]

http://www.servovendi.com/uk/waterproof-ph-meter-and-temperature-tester-adwa-0-01-ph-ad12.html

Thanks.

 

[trevgale]

From most information I have seen the mash pH should basically stabilise within 15min and remain stable for the rest of the mash, it may change by a very small amount. It will probably change during sparging.

The amount of change I was seeing make it pointless to try and use to calculate water adjustments.

 

[MHB]

Not really sure. The article didn't really seem to say. MHB may have some idea.

Nah - I'm a bucket chemist you would need someone that can work with Ksp without running out of fingers, I might be able to dig out the right ref books and spend several hours trying to remember stuff that I haven't done for way too long.

Just happens that I was having this exact conversation with Keith at Potters a couple of weeks ago, I'm pretty sure he has a masters in inorganic chemistry and doesn't regard physical chemistry as a perversion, personally I can see why one would give up on a PhD and go brewing.
Mark

 

[mattjm]

When I was in the market for a PH meter recently, I was steered away from the AD12 (which I really wanted) towards the AD11 by the sales guy. The basic reasoning was that he could not in good faith tell me that the higher model was anymore accurate and that it was basically the same meter with an extra point resolution display. Based on that I ended up going with the AD11 with +/-0.1 accuracy. I paid $110 and it is my first meter so I have little more than the buffer solutions to guage accuracy from.
It is my understanding that for accuracy sake on the AD12 you should ignore the second decimal place completely.