PH Meters
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tjpfeister
Well-Known Member
These dirt cheap ones have been my answer:
http://www.amazon.com/Digital-Meter-PH-009-Multimeter-Tester/dp/B0054IQCB4/ref=pd_sim_86_3?ie=UTF8&dpID=41Wuy-aV5xL&dpSrc=sims&preST=_AC_UL160_SR160%2C160_&refRID=016J68QR5Z0E6VFGA991
And to be clear, I am not afraid to spend money on brewing equipment. In fact, I have purchased more expensive units and been miserably upset with them. Just get yourself some large jugs of calibration fluid and you'll be set.
I have been eyeballing this unit:
http://www.amazon.com/gp/product/B001DTNDME?psc=1&redirect=true&ref_=ox_sc_sfl_title_5&smid=ATVPDKIKX0DER
But it's sold by Milwaukee (which means that it can probably be had for less if you find the chinese manufacturer, like the little yellow one I posted above) and secondly... I have had bad experience with pricier meters.
$.02
http://www.amazon.com/Digital-Meter-PH-009-Multimeter-Tester/dp/B0054IQCB4/ref=pd_sim_86_3?ie=UTF8&dpID=41Wuy-aV5xL&dpSrc=sims&preST=_AC_UL160_SR160%2C160_&refRID=016J68QR5Z0E6VFGA991
And to be clear, I am not afraid to spend money on brewing equipment. In fact, I have purchased more expensive units and been miserably upset with them. Just get yourself some large jugs of calibration fluid and you'll be set.
I have been eyeballing this unit:
http://www.amazon.com/gp/product/B001DTNDME?psc=1&redirect=true&ref_=ox_sc_sfl_title_5&smid=ATVPDKIKX0DER
But it's sold by Milwaukee (which means that it can probably be had for less if you find the chinese manufacturer, like the little yellow one I posted above) and secondly... I have had bad experience with pricier meters.
$.02
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Send me the $7 and when you brew drop me an e-mail and I'll tell you what your pH is. The results (which will be my guesses) will probably be more accurate than any measurement made with this meter. Think about it for a minute. The meter has to be manufactured, shipped to the US, warehoused, distributed etc and some one has to be making a profit. How much is the meter then really worth? Does anyone really think it possible that a pH meter worth perhaps $2 is going to be a viable alternative for pH measurement? The specs by themselves (±0.1 pH) admit that this unit is not suitable for brewing.
This is a more reasonable choice and is, in fact, one of the three meters with which the readership of HBT seems to have had good luck. The other two are the Hach pHPro+ and the Omega equivalent.
I have too but they have always been resolved. If you need the bells and whistles (multiple channels, ability to connect to a computer, data logging, ISE, ORP... ) you are going to pay more but most of us don't need those things. Higher end electrodes (which alone may cost hundreds of dollars) often return the investment by lasting for over 5 years, having clearable and/or refillable junctions etc.
Have a look at the pH calibration sticky at the top for further insight.
PS: The Milwaukee meters were made in Romania and now, I believe, in Italy.
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For the homebrewer, spending a bunch of money on a pH meter may not make sense. But spending very little on junk doesn't make sense either. Buying from a reputable brand like Hach, Omega, Oakton, Milwaukee, etc. does help assure quality (or at least support in resolving quality issues). However, brand name doesn't provide assurance by itself. Many of those brands do sell less reliable equipment and you should stay away from those units.
I have been an advocate of meters that have 0.01 unit resolution and also have a cabled, BNC-connector equipped pH probe. Poor resolution meters and being tied to a non-replaceable or proprietary probe, is not worth your money. Remember, a pH probe will always be a friable piece of equipment and it will have to be replaced eventually. Poor design or construction and mistreatment of the probe by inserting into hot liquids or failing to keep it stored in a proper solution or setting will mean that you will have to replace prematurely. Buying a meter with an easily and inexpensively replaceable probe seems to be a wise move to me. I've had a Milwaukee MW-101 for about 5 years now and it has performed well.
I have been an advocate of meters that have 0.01 unit resolution and also have a cabled, BNC-connector equipped pH probe. Poor resolution meters and being tied to a non-replaceable or proprietary probe, is not worth your money. Remember, a pH probe will always be a friable piece of equipment and it will have to be replaced eventually. Poor design or construction and mistreatment of the probe by inserting into hot liquids or failing to keep it stored in a proper solution or setting will mean that you will have to replace prematurely. Buying a meter with an easily and inexpensively replaceable probe seems to be a wise move to me. I've had a Milwaukee MW-101 for about 5 years now and it has performed well.
MagicMatt
Brewmathemagician
Listen to what these guys say; their word is gospel in the brew science world!
My 2 cents, if I may - I own a Hanna pHep, which I consider to be a middle-of-the-road pH meter. It's not the best by far, but it's definitely nothing to balk at. And if you find it on sale, the price makes it worthwhile. For instance, if I had to pick one pen to recommend to brewers, it would likely be the Hach pHpro+, as it's pretty reasonably priced (at around $150 or so on sale) and more than suitable for brewing purposes. However, I got the Hanna pHep for about $70 from Amazon a while ago. Check this site to see how the price has flucuated recently, and you can keep an eye out for it going on sale. At about 1/2 the price as the Hach model, I'd say this one can't be beat for a decent reliable meter.
My 2 cents, if I may - I own a Hanna pHep, which I consider to be a middle-of-the-road pH meter. It's not the best by far, but it's definitely nothing to balk at. And if you find it on sale, the price makes it worthwhile. For instance, if I had to pick one pen to recommend to brewers, it would likely be the Hach pHpro+, as it's pretty reasonably priced (at around $150 or so on sale) and more than suitable for brewing purposes. However, I got the Hanna pHep for about $70 from Amazon a while ago. Check this site to see how the price has flucuated recently, and you can keep an eye out for it going on sale. At about 1/2 the price as the Hach model, I'd say this one can't be beat for a decent reliable meter.
motobrewer
I'm no atheist scientist, but...
I'm about to pull the trigger on a Milwaukee MW101. I like it better than the MW102 because of the manual calibration.
The pHep (pH electronic paper) is a very frustrating unit in the sense that it is quite stable but grabs the calibration readings when it wants to, not when you tell it to and that is before the reading is really stable so it is impossible to cal this guy properly. Given the good stability, however, you could re-measure the two buffers just after cal, plot the pH correction needed at 4 and 7, connect the two points with a straight line and use that as a calibration correction 'curve'.
Why, we can't help wondering, do you prefer to do things the hard way?
How's it do on the stability test? I ask this because their literature artfully dodges the question of accuracy.
motobrewer
I'm no atheist scientist, but...
i should probably do one again.
I need a class on how to care for a PH meter. I have 2 that I have barely used and neither one works now.
Tried the little red Hanna one and the beige Milwaukee one with similar bad results.
I would hate to spend a bunch of money again on a PH meter and have it not last. What are your tricks to extend the life of the electrode?
Tried the little red Hanna one and the beige Milwaukee one with similar bad results.
I would hate to spend a bunch of money again on a PH meter and have it not last. What are your tricks to extend the life of the electrode?
Looks pretty good to me. Yes, checking up on the things every 6 mos or so is a good idea (not that I do it).
While the technology is much, much better than it was only a couple of years ago (I've had electrodes go 5 years and more) a pH electrode does not last for ever. See https://www.homebrewtalk.com/showthread.php?t=302256 for some tips on how to use and care for one.
Because I can cheaply make my own 9.2 and 3.56 pH buffer solutions (distilled water and sodium metaborate or potassium bitartrate, respectively), and just buy the 7.01. Or maybe just buy the 7.01 and 4.01. Or just do it once to prove to myself that I can.
10.01 pH buffer is perishable due to absorption of atmospheric CO2. I don't really know how long a bottle of it keeps but I'm pretty sure it has an expiration date.
You can make the others pretty easily/cheaply too. Bipthalate for the 4, phosphate for the 7. But when you make a buffer you have to either dry the chemicals before weighing, weigh very precisely or 'trim' the buffer (with acid or base) against a known set of standards. Unless you are NIST you have to get those standards from NIST or a NIST traceable source. There's a big discussion going on in another forum discussing why people don't do more things themselves. Certain things are best left to professionals such as brain surgery and making buffers (my opinion obviously). I do most everything myself but am more than happy to pay someone else to make buffers for me.
I applaud that and interpret your remarks to indicate that you are really interested in seeing if you can make a good buffer. How will you know if you have succeeded unless you have the best meter you can get calibrated against the best buffers?Or maybe just buy the 7.01 and 4.01. Or just do it once to prove to myself that I can.
All digital meters (that does not include analog meters with a digital voltmeter like the MW101) have ATC and calibration built in. There is no way to take them out of a digital meter. They know the pH's of the standard buffers as a function of temperature and many of them can handle buffers other than the standard NIST traceable technical buffers. If you want to experiment with buffers I would suggest getting the best (most stable) meter you can afford and calibrating it with standard buffers prepared by a laboratory equipped to do all that accurate weighing and trimming I referred to either. Calibrate your meter with those buffers but do not rely on ATC to correct for temperature differences in the buffers. Put them in a water bath and when measuring your samples put them in the water bath too. This is because the isoelectric pH of your meter isn't exactly 7.000 and the algorithms assume that it is. Why not solve this problem by using an analogue meter? You can't. In order to determine pH from a meter calibrated with two buffers you must know the temperature of each of the two buffers and the sample and you must know pHi (the isoelectric pH). If you want best accuracy and ATC you must first estimate pHi from measurements on the electrode's mV output at different temperatures and then process the sample readings' mV outputs to determine pH based on slope, offset and pHi. This is what I do. My fancy pH meter is just a mV meter but it will transfer a reading to a computer on demand.
They all have expiration dates (which are pretty short but then the shorter the life, the more buffer they sell) which should be marked on the container. I am particularly concerned about the 10 buffer because of CO2 pickup. I almost never do 3 point calibrations because
1)In brewing we seldom measure critically above 7
2)The dilution of precision from a 4/7 cal isn't bad up to say pH 8.5 (but it's not as good as the DOP from a 3 point cal.
Of course if I have a fresh bottle of 10 buffer I'll do a 3 point but I don't really trust 10 buffer once it's been opened. Wonder how the 'powder pillows' buffers are in this regard.
I think I only need 0.1 pH point of accuracy for brewing, but I want that extra digit of precision so I can see the value moving. (does that make sense?)
It looks like the MW-101 meter only has 2 points of calibration (first you set the intercept with the 7.01 solution, then you set the slope with either 10.01 or 4.01 solution, depending which side of 7 you care most about that day.
Here's the article that put the idea in my head about making my own borate buffer.
And a saturated solution of potassium bitartrate (cream of tartar) is a NIST standard pH buffer.
I want to test it and see if it really works I'll need real buffers the first time, then I can test my homemade ones against them. I think the meter comes with one set of 20ml buffer packets.
It looks like the MW-101 meter only has 2 points of calibration (first you set the intercept with the 7.01 solution, then you set the slope with either 10.01 or 4.01 solution, depending which side of 7 you care most about that day.
Here's the article that put the idea in my head about making my own borate buffer.
And a saturated solution of potassium bitartrate (cream of tartar) is a NIST standard pH buffer.
I want to test it and see if it really works
I'll need real buffers the first time, then I can test my homemade ones against them. I think the meter comes with one set of 20ml buffer packets.
LandoLincoln
Well-Known Member
First one I purchased: Milwaukee pH 600 for about $30. Total waste of money. Only had accuracy into the tenths so it just wasn't accurate enough for testing wort. Might be useful for testing the pH of Star San, but that's about it.
Second one I purchased: HM Digital PH-200 for about $80. Very disappointing. Worked about about six months, then the readings started going crazy. Bought a $50 replacement sensor tip for it but that didn't help.
Third one I purchased: Hach Pocket Pro+ for about $130. Finally found one that wasn't a piece of junk. Has accuracy into the hundreths, two-point calibration and has a replaceable sensor tip. Has worked very well for the past year.
No pH meter is designed to last very long, though. Getting accurate pH readings is an expensive proposition.
Yes, absolutely and thats precisely why you need a meter that reads to 0.01 precision. At 0.1 precision we might pretend that the meter reads pH precisely, multiplies the reading by 10, then applies the floor function and finally multiplies by 10. 0.1*floor(10*5.01)/10 = 5.0. 0.1*floor(10*5.099) = 5.0 so the pH can change by 0.1 and the meter reads the same. You make a correction with x mL of acid, see no change and then make another correction by the same amount and overshoot.
That's right. But, OTOH, it is rare that you need a multipoint calibration. With a meter than can read temperature to about half a degree and voltage to about 0.2 mV you can, with NIST traceable ±0.02 buffers achieve accuracy of a bit better than ±0.02 pH half way between 4 an 7 buffers which is, fortuitously, right where mash pH falls.
Then why don't we use it in every day use? Probably has to do with the practicalities of preparation, storage, etc. It is actually a better buffer (higher buffering capacity) than the biphthalate technical buffer most of us employ for daily calibrations.
I want to test it and see if it really works
You know where to get the borate. You might have more trouble finding the bi tartrate but it is certainly easy enough to make using tartaric acid from the home brew shop. Make a solution and then just titrate with NaOH (also sold by home brew shops that also serve vintners) until the pH is where you want it. This is a perfectly legitimate way to make a buffer though not as easy as just making a saturated solution of pure bitartrate if you can obtain it.
You will want to obtain a supply of buffers as fresh buffer should really be used for each calibration. Many of us find the powder pillow buffers (Hach) or capsules (Omega) are a convenient way to have fresh buffers handy but, of course, one needs to prepare them each time (a simple matter) and have a source if DI water available.
Well I did say 'pure' but there is probably no reason to suppose that McComicks cream of tartar is appreciably less pure than the tartartic acid one would buy from the home brew shop.
Now the potential problem here stems from the fact that McCormick, in making this product, does exactly what I suggested that you do i.e. add NaOH to tartaric acid until some pH is reached. The difficulty is that they may not necessarily pick 3.665. Note that even if they do the resulting powder that is left after the water is evaporated is not pure bitartrate but a mix of bitartrate salt (74%), tartaric acid and the tartrate salt. If you put pure bitartrate salt into pure water you will attain that same mix but in buying the food product you have no guarantee that they went to the pH that maximizes the bitartrate ion concentration. Thus you have to do essentially what I suggested in the last post which is to measure the pH against known standards and trim with NaOH if the pH is low or with HCl if it it is high. If you could get pure bitartrate you do not have to check against other standards as bitartrate is not only a standard but is, in fact, one of the bench marks by which the pH scale is defined in the same sense that the temperature scale is defined by the triple point of water.
Now the potential problem here stems from the fact that McCormick, in making this product, does exactly what I suggested that you do i.e. add NaOH to tartaric acid until some pH is reached. The difficulty is that they may not necessarily pick 3.665. Note that even if they do the resulting powder that is left after the water is evaporated is not pure bitartrate but a mix of bitartrate salt (74%), tartaric acid and the tartrate salt. If you put pure bitartrate salt into pure water you will attain that same mix but in buying the food product you have no guarantee that they went to the pH that maximizes the bitartrate ion concentration. Thus you have to do essentially what I suggested in the last post which is to measure the pH against known standards and trim with NaOH if the pH is low or with HCl if it it is high. If you could get pure bitartrate you do not have to check against other standards as bitartrate is not only a standard but is, in fact, one of the bench marks by which the pH scale is defined in the same sense that the temperature scale is defined by the triple point of water.
AJ, this has been very educational. Thank-you. (and I hope it hasn't been too frustrating for you.) I was conflating "Food grade" with "purity". They're related but not the same thing.
Of course I'm going to test the pH of the McCormicks cream of tartar, but won't rely on it as a standard.
The borax OTOH, I might use as a standard, if it works. I don't think I'll need a high-pH buffer very often, and when I do it doesn't need to be as accurate as the low-pH buffer.
Of course I'm going to test the pH of the McCormicks cream of tartar, but won't rely on it as a standard.
The borax OTOH, I might use as a standard, if it works. I don't think I'll need a high-pH buffer very often, and when I do it doesn't need to be as accurate as the low-pH buffer.
Educational for me too. If I don't keep fiddling with this stuff the hinges get rusty! And I have learned some things too.
Food grade essentially means safe i.e. packaged in a facility inspected and certified as suitable for packaging foods and of course the materials themselves will be limited as to how many heavy metal salts they contain but there chemically purer grades. For best results you should have pure potassium dipthalate which, as it is a benchmark on the pH scale, is manufactured as a NIST SRM (Standard Reference Material) and you can get it for a mere $443 for 60 grams. Turns out the stuff scraped out of wine barrels is easily purified and what you buy is over 99% pure. This means that the buffering action you seek is certainly going to swamp the effects of the impurities.
