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Hanna Ph Meters With Automatic Temperature Compensation


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#1 Andy in SoCal

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Posted 13 November 2010 - 05:34 PM

I have two Hanna pH meters with ATC (Auto Temp Compensation) and discovered today that the meters give different readings as the temp of the sample changes. ie, as the sample gets colder the pH reading goes lower, instead of staying the same which is what ATC would seem to mean.

Very frustrating!

Andy
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#2 red_feet

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Posted 13 November 2010 - 07:09 PM

I have two Hanna pH meters with ATC (Auto Temp Compensation) and discovered today that the meters give different readings as the temp of the sample changes. ie, as the sample gets colder the pH reading goes lower, instead of staying the same which is what ATC would seem to mean.

Very frustrating!

Andy


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#3 SBS

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Posted 13 November 2010 - 07:15 PM

I have two Hanna pH meters with ATC (Auto Temp Compensation) and discovered today that the meters give different readings as the temp of the sample changes. ie, as the sample gets colder the pH reading goes lower, instead of staying the same which is what ATC would seem to mean.

Very frustrating!

Andy


Andy, I have the PHep 5. As a data point, last night I was testing wine as the temp was rising and it was adjusting & compensating accordingly from 36F all the way to 68F. Reported the samev PH all the way through the temp range. So , maybe you have a different meter?

Steve


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#4 Andy in SoCal

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Posted 13 November 2010 - 07:21 PM

maybe you have a different meter?

Steve

Hi Steve, I have two Hanna pHep HI 98128 meters and crushed some grenache today.

iirc, the ph went from about 3.78 at about 105F (after a quick microwaving to drive off CO2) to about 3.55 at 64F. On both meters. I then tested water and saw pretty similar shifts due to temp.

How do we know if/when we are getting a true reading?

Andy
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#5 SBS

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Posted 13 November 2010 - 09:36 PM

Hi Steve, I have two Hanna pHep HI 98128 meters and crushed some grenache today.

iirc, the ph went from about 3.78 at about 105F (after a quick microwaving to drive off CO2) to about 3.55 at 64F. On both meters. I then tested water and saw pretty similar shifts due to temp.

How do we know if/when we are getting a true reading?

Andy


Andy, yes that is the same meter as mine - HI 98128 aka pHeP5 .

Sooooooo, since I too have experienced frequent head scratching moments with my Hanna meter, I decided to run down to my man cave and attempt to simulate your situation. I did not even get off the launch pad. First I calibrated the meter. Them I tested tap water at 66F... got PH = 7.5. Then I tested distilled water & got 5.6. in both situations after about 6 or 7 different tests, the meter would fail to quickly narrow down to the final number, meaning it would take several minutes to get to a final number. Also, if I stirred the meter in either liquid it would quickly "drop" a few tenths and then go back up slowly.

In between these tests, I would occasional go back to my buffer solutions, since I was confounded by the behavior of the meter....BANG right on within 5-7 seconds. same thing with a previously tested wine sample.

I had previous issues and Hanna sent me a new electrode and it was also erratic, but then a day later both electrodes were perfect........bizarre.

I think these Hanna meters are VERY INCONSISTENT!

The only thing I can think of is that the cap for the meter which holds the storage solution somehow is not sufficient and the meter dries out, and then give poor results. I notice that when I use it daily it appears more consistent.

Steve


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#6 Andy in SoCal

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Posted 15 November 2010 - 03:13 PM

Steve, I've just spent a lot of time researching this. I haven't worked out quite all the ins and outs quite yet, but basically...

pH meters give less accurate (and slower) readings the farther the sample temperature is away from 25C/77F.

The ATC feature does compensate for the loss of accuracy of sample temps at other than 25C/77F, so a pH reading at 40F by an ATC pH meter tells you accurately the pH of your sample at that particular temp, ie, 40F.

However, the pH of a solution varies with its temperature, so a pH meter will, for example, give different readings of the same sample when that sample is at, say, 40F vs. 80F.

So probably the best practice is to always have the temp of the must sample at the same (and constant) temp every time you test, like around 25C/77F.

Also, it helps accuracy to have the buffers you use to calibrate the pH meter be at the same (and constant) temp as the samples you'll be testing.

Also, if the meter is warmer or cooler than the sample, that can cause problems too as its temp and the sample's temp constantly change as they both try to come to an equilibrium temp when you put the meter in the sample to test.

My thought now is to immerse the buffers, samples and pH meters in a water bath at room temp (which should be close enough to 25C/77F) until everything is the same temp, and then test keeping the samples in the water bath.

pH testing is, for me anyway, by far the weakest and most frustrating link in the whole homie wine making process, and I'm determined to tame the beast!

Best,

Andy
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#7 aderoy

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Posted 06 December 2010 - 12:07 PM

Hi Andy,

Hanna is trying to stay active in these forums as another avenue of communicating directly with users of our products.

The ATC feature is only one variable that could contribute to variances in readings from one meter to the next. When you read the temperature of the sample with the two meters, is the temperature consistent on both meters?

A more important variable is the performance and condition of your pH electrode. pH electrodes have a reference that is suspeptible to clogging when used in wine. It is critical they be maintained properly. There is a cleaning solution and technique that we recommend as well as a storage solution so the electrode stays saturated when it is not being used. It is with the pH electrode that I would be more inclined to believe as to why you may be seeing a variance.

In addition, one of our sales or technical reps, can talk to you about determining the slope of your electrode. Depending on the meter(s) you have, we can determine if the electrode is drifting outside of an acceptible accuracy range.

We have sales professionals dedicated to assisting winemakers all over the country. Please feel free to contact them at any time. They are Dave Adams - dadams@hannainst.com and Chris Kearney - ckearney@hannainst.com

I also attached a pdf on electrode maintenance and a whitepaper we whote that I thought you might find helpful. We also have a lot of data on this subject on our website in our knowledge base and white paper sections.

Thank you again.

Hanna Instruments.
800-426-6287


I have two Hanna pH meters with ATC (Auto Temp Compensation) and discovered today that the meters give different readings as the temp of the sample changes. ie, as the sample gets colder the pH reading goes lower, instead of staying the same which is what ATC would seem to mean.

Very frustrating!

Andy

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#8 Andy in SoCal

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Posted 06 December 2010 - 02:27 PM

Hi (Roy?),

Thank you for proactively reaching out to me/us.

To answer your question, iirc, both meters read a slightly different temp while I was testing. I think it was only a few degrees different, meter to meter.

Both of my meters are Hanna pHep HI 98128's. One is brand new, bought in August. The other is older however its electrode is also brand new, bought in August.

Thank you for your info and the attached documents, they are very informative. I will also explore your website as you suggest.

I would like to mention, though, the pH meter maintenance item that is probably the most difficult for me/us winemakers to consistently achieve is keeping the electrode saturated when not use.

In winemaking it is often several/many months between pH meter uses, and the cap provided with the meters does not adequately keep the storage solution from evaporating.

Best,

Andy
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#9 D&S

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Posted 06 December 2010 - 02:49 PM

I would like to mention, though, the pH meter maintenance item that is probably the most difficult for me/us winemakers to consistently achieve is keeping the electrode saturated when not use.

In winemaking it is often several/many months between pH meter uses, and the cap provided with the meters does not adequately keep the storage solution from evaporating..........



Don't use the cap at all. Why not place the meter in a small (50mL) beaker or glass with some electrode storage solution and wrap it with parafilm or saranwrap.



#10 Andy in SoCal

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Posted 06 December 2010 - 04:29 PM

Don't use the cap at all. Why not place the meter in a small (50mL) beaker or glass with some electrode storage solution and wrap it with parafilm or saranwrap.

Great idea, I like the way you think!

With the clear container you can see at a glance whether the solution needs replenishing.

Andy
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#11 homer

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Posted 26 December 2011 - 05:03 PM

I have two of the Inexpensive Hanna PH meters ($30), I did not know that temp affected the readings that much, are the expensive ones better? Trying to get the samples to 77 degrees would be a real pain. bk

#12 dagobob

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Posted 27 December 2011 - 08:00 AM

Just a word of caution, I have a Hanna HI 98108 pH meter that comes with a cap for storing the meter in solution. I got tired of the reference solution always drying out between use so I wrapped a small piece of black electrical tape around the cap. However, the solution then proceeded to evaporate and crystallize INSIDE of the meter which caused the electrode to corrode. I had to get a new electrode. Fortunately just the electrode is replaceable in that model, but it still cost a fair amount of $$$.

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