Author Topic: pH Meters  (Read 4498 times)

Offline denny

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Re: pH Meters
« Reply #15 on: February 15, 2010, 02:11:30 PM »
I have had 2 of these: http://www.hannainst.com/usa/prods2.cfm?id=031003&ProdCode=HI 98128  although it was 0.01 accuracy when I got it. The first lasted several years. The second only lasted 1-2 years, but I didn't store it in the storage solution.
Now I have a Milwaukee.
Get the calibrating solution in 16 oz bottles from your local science supply store.

What model of Milwaukee, Tom?
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Offline tom

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Re: pH Meters
« Reply #16 on: February 15, 2010, 05:05:19 PM »
SM 102. It has a separate temperature probe and automatic calibration.

Kai likes the SM 101 because it has manual calibration. I think he had a previous meter that stopped automatically calibrating. But it doesn't have a temperature probe.

I like the temperature probe to make sure I'm not putting the pH probe in wort that's too hot. Of course you can get your own separate thermometer! And you probably already have one of those.

Brew on!
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Offline denny

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Re: pH Meters
« Reply #17 on: February 16, 2010, 10:04:13 AM »
Well, I think I'm gonna pull the trigger on the pH51.  May not be the best meter out there, but it looks like it will fulfill my needs....and besides, my BIL is paying for it!  :)
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Offline euge

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Re: pH Meters
« Reply #18 on: February 16, 2010, 10:58:30 AM »
I just posted some similar questions in the equipment section, but I'll repeat them here....I'm looking at a Milwaukee pH51 at the LHBS.  According to Kai's buyers guide, I should be looking for an accuracy of .01ish.  If I read this correctly (http://www.milwaukeetesters.com/pdf/pH51.pdf), the pH 51 is only .1?  All I'm really interested in is mash pH, and Kai's writeup implies that might be OK for that that purpose.  Anybody used this model?

Denny, the resolution and variance for that model are both 0.1 pH. I don't really see where a resolution to a hundredth in homebrewing would help any more than a tenth. But, always nice to have.

That unit has a manual callibration screw and replaceable electrode. Nice!
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Offline Kaiser

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Re: pH Meters
« Reply #19 on: February 16, 2010, 11:06:30 AM »
Denny, the resolution and variance for that model are both 0.1 pH. I don't really see where a resolution to a hundredth in homebrewing would help any more than a tenth. But, always nice to have.
 

If you’re just looking to check mash pH and maybe also boil pH an accuracy of +/- 0.1 should be fine. If you have greater resolution you can also use it to check your beer pH and detect if you have problems with autolysis for example. That causes an unusually high rise in beer pH after fermentation. I never noticed anything dramatic but I thought of it when I opted for higher precision model. I also needed better precision to do the mash pH experiments I did.

Kai

Offline denny

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Re: pH Meters
« Reply #20 on: February 16, 2010, 11:09:20 AM »
I can see why you'd prefer a higher res for the work you do, Kai, but I'm just looking for something better than the ColorpHast strips I've been using.  I think this will be OK for my purposes.  Thanks for your comments!
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Offline euge

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Re: pH Meters
« Reply #21 on: February 16, 2010, 11:20:29 AM »
Denny, the resolution and variance for that model are both 0.1 pH. I don't really see where a resolution to a hundredth in homebrewing would help any more than a tenth. But, always nice to have.
 

If you’re just looking to check mash pH and maybe also boil pH an accuracy of +/- 0.1 should be fine. If you have greater resolution you can also use it to check your beer pH and detect if you have problems with autolysis for example. That causes an unusually high rise in beer pH after fermentation. I never noticed anything dramatic but I thought of it when I opted for higher precision model. I also needed better precision to do the mash pH experiments I did.

Kai


Thanks Kai! I also have  been concerned with this. Didn't know about the pH upswing. I got a beer that sat on the yeast a little too long for my preferences. Taste test gives me "umami" and I'm worried. I don't have a reference but the pH will get checked anyway.

Denny, I had to get a meter since the pH strips I got from the LHBS were total crap. The resolution was 2. Yes 2! Not 0.2... extremely difficult to decide what the pH is and when the digital got used how off I was became very apparent. However the Colorphast has a "narrow range" http://www.sanitationtools.com/products.asp?category=72&attriberror=true&Product=1391 which should be better.
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Offline denny

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Re: pH Meters
« Reply #22 on: February 16, 2010, 11:51:01 AM »
However the Colorphast has a "narrow range" http://www.sanitationtools.com/products.asp?category=72&attriberror=true&Product=1391 which should be better.

Those are the ones I use, but I started wondering about them because it seems like my pH always shows up in range, even for a variety of beer colors.  I even ordered a new pack recently in case my older ones had gone bad.  Maybe I'm colorblind and just can't see the changes in them....
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Offline Tim McManus

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Re: pH Meters
« Reply #23 on: March 21, 2011, 12:46:56 PM »
Rather than start a new thread about pH meters, I thought I would resurrect this one since I found an earlier thread that referred to it.

I have some meter questions for the experienced and experts out there.

I recently picked up a Milwaukee ph56 from Cynmar and will be using it to test the pH of our darker beers.  Some of the questions I have are specific to this model, but the answers might be useful for other meters as well.

We brew anywhere from 1-4 batches a month of various styles.  Although the intent was to test the darker beers, I'll probably use them for all beers just because I can.  Do I need to calibrate the meter before each batch, or is it more of a once every x months sort of thing?

I understand that I need to store it in a 4.01 solution or bottled water to keep the probes wet.  The ph56 comes with cap over the probes.  Is this something that I should fill with the solution, or should I get a small beaker and leave the probe in there?  I am worried about evaporation and some klutz (me) knocking the solution over.  Does anyone have any suggestions on storage?  It came with a nice case, but if I have to store it wet, the case becomes kind of useless.  Also, when I transport it to the brewery, do I need to do it in the solution, or can I remove it from the solution for the 10-minute drive and subsequent 5-6 hour brew day?

Based on my brewing frequency noted above, should I buy bottles of calibration solution or packets?  Packets seem more convenient since I can grab a 4.01 and a 7.01 and be set for the day, but bottles are probably cheaper in the long run.  I am worried about spoilage since the solutions are dated.  Does the solution degrade with exposure or time?

Thanks in advance!
Tim McManus
Haskell, NJ

Offline Kaiser

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Re: pH Meters
« Reply #24 on: March 21, 2011, 02:07:56 PM »

We brew anywhere from 1-4 batches a month of various styles.  Although the intent was to test the darker beers, I'll probably use them for all beers just because I can.  Do I need to calibrate the meter before each batch, or is it more of a once every x months sort of thing?
My experience has been that calibration is not necessary very often. I now do it maybe once a month or before a series of experiments and even then I find that it is only off by 0.01 – 0.02 units. Check the pH of the buffers once in a while to see how much drift you are actually getting.

Quote
I understand that I need to store it in a 4.01 solution or bottled water to keep the probes wet.  The ph56 comes with cap over the probes.  Is this something that I should fill with the solution, or should I get a small beaker and leave the probe in there?

To my knowledge pH meters should not be stored in their buffer solutions. They come with storage solution and you should buy an additional bottle. The storage solution is usually saturated potassium chloride (KCl), which is the same solution that’s inside the probe.

Keep some storage solution in the cap. Just enough that it doesn’t come out when you insert the probe. Also store the tester upright. I’m not sure what Milwaukee’s recommendations are but I’d make a stand that the tester can stand upright in.

Quote
Based on my brewing frequency noted above, should I buy bottles of calibration solution or packets?  Packets seem more convenient since I can grab a 4.01 and a 7.01 and be set for the day, but bottles are probably cheaper in the long run.  I am worried about spoilage since the solutions are dated.  Does the solution degrade with exposure or time?

I doubt the solutions expire. They are inorganic compounds. I have one 500 ml bottle of 4.00 and 7.00 calibration buffer each. I also have 4 oz bottles where I keep 2 oz of the buffer for calibration. Although this is not recommended I actually reuse the calibration buffers over the course of 6-8 months. They are so strong that their pH doesn’t drift more than 0.02 units during the time that I use them over and over again. But I also make sure that I rinse the probe with RO or DI water before I put it into any of the calibration buffers. Reusing pH buffer solution keeps me from having to buy new ones all the time.

Kai

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Re: pH Meters
« Reply #25 on: March 21, 2011, 02:17:58 PM »
You can create your own storage solution by dissolving potassium chloride into pH 4 buffer solution at a rate of 10 grams per 100 ml of liquid.  It takes a day or two to dissolve the KCl.  I've read that it is preferrable to use a slightly acidic solution.  The buffer solution supposedly also has mold inhibitors in it.

I used a White Labs vial which holds about 40 mL of liquid and I added 4 grams of KCl.  I drilled a hole in the cap of the vial to tightly fit my probe.  I then wrapped a wire around the vial and attached it to the peg board on my bench.  I always know where the meter is and its storage solution. 

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Offline Tim McManus

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Re: pH Meters
« Reply #26 on: March 21, 2011, 02:46:30 PM »
Thanks, guys.

Too bad the ph56 doesn't have a flat bottom on the bottom cap.  It would have made it easier to fill the cap reservoir with storage solution and stand the unit upright.

I too was eyeing a white labs vial to convert into a storage solution reservoir.  Now all I need to do is make a stand for it.

Oh, and the reason I asked about the long-term stability of the solution was because the packets of 4.01 and 7.01 that shipped with the ph56 have expiration dates.  Mine expire in 7/2015, so I think I'll get a 230 ml bottle of each and it should last me several years.
Tim McManus
Haskell, NJ

Offline punatic

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Re: pH Meters
« Reply #27 on: March 21, 2011, 08:52:22 PM »
The acidic pH 4 buffer/KCl storage solution keeps scale from building up on the pH probe's bulb.  This scale is what causes the pH meter to be slow to settle on the pH value as the probe ages.  Slow probes can also be revitalized by soaking them in a mild citric acid solution over night. 

Rinsing pH probes after every measurement is key to probe life.  Keep a squeeze-bottle of DI water at hand when measuring pHs.  Keep the pH probe wet at all times.  DI water is cheap.  pH probes are not.
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Offline johnf

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Re: pH Meters
« Reply #28 on: March 21, 2011, 09:04:44 PM »
I calibrate every day of use because, why not?

If I didn't I would at least check the pH of buffer if I got a suspect reading and I would calibrate daily for the first dozen or so brew days because otherwise I wouldn't be able to judge what a suspect reading was.

If you are worried about the cost, you can purchase pillows of powdered buffer that you mix with a measured amount of water. These can be much, much, less expensive than buying liquid at a home brew shop and may make you rethink the dollar cost of frequent calibration.

Offline punatic

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Re: pH Meters
« Reply #29 on: March 21, 2011, 09:32:23 PM »
I calibrate every day of use because, why not?


We calibrate each pH meter at least once every workday, and record the calibration data in a logbook (spreadsheet).
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