I am looking at investing in a pH meter. I've been doing some reading on various models but would like some input from those of you who already own one. It looks like there are a few models out there under $100. Can anyone provide input on what I should be looking for? wet/dry storage, calibration needs, temperature adjustment, resolution and margin for error, etc?
pH Meter Suggestions?
- Thread starter winvarin
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DrJerryrigger
Well-Known Member
I'm not an expert but know about the two I have:
cheapo $30 one (don't know the name off hand but it's yellow with a black cap) read out: X.X similar to this one
A bench top one made by (or for) Corning It has a hand wand on a ~two foot wire, it would have likely cost a few hundred dollars (long story, but I payed five bucks) read out: X.XX looks like this one
Both need to be calibrated with a solution. The cheap one can only be calibrated to one point (I use 7). It seems to be right on at 4 after this calibration though.
The fancy one needs to be calibrated to 4, 7, and 10. This is a PITA because it is a rather complicated device with too many functions. Once it is set up, it gives a accurate read out much faster, that is to say; the numbers stabilize quicker. I almost never use this one, due to the complication of using it, and fear I will break it.
I'm quite happy with my cheap one, and if I drop it in a mash, i won't be that upset. So I would recommend finding a cheap one (maybe used) on ebay. I think that most of them are listed in home and garden for use in hydroponic plant growing. If you really feel you need to see .01 resolution there are some $100 hand held ones that claim to be water proof
cheapo $30 one (don't know the name off hand but it's yellow with a black cap) read out: X.X similar to this one
A bench top one made by (or for) Corning It has a hand wand on a ~two foot wire, it would have likely cost a few hundred dollars (long story, but I payed five bucks) read out: X.XX looks like this one
Both need to be calibrated with a solution. The cheap one can only be calibrated to one point (I use 7). It seems to be right on at 4 after this calibration though.
The fancy one needs to be calibrated to 4, 7, and 10. This is a PITA because it is a rather complicated device with too many functions. Once it is set up, it gives a accurate read out much faster, that is to say; the numbers stabilize quicker. I almost never use this one, due to the complication of using it, and fear I will break it.
I'm quite happy with my cheap one, and if I drop it in a mash, i won't be that upset. So I would recommend finding a cheap one (maybe used) on ebay. I think that most of them are listed in home and garden for use in hydroponic plant growing. If you really feel you need to see .01 resolution there are some $100 hand held ones that claim to be water proof
Hermit
fuddle
Probably a good point in that the cheaper one may be better than nothing and still as accurate as the strips.
DrJerryrigger
Well-Known Member
oh, I didn't mention temp. It's one of those things; do you want to know your PH so that you know the beta & alpha amylase can do there thing, or do you want to know more information that you could possibly use because your nerdy like that (a good thing in my book). If that latter is true, get a snazzy one, if not get a junk one.
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winvarin
Well-Known Member
I'm in between. I have been delving more deeply into the water chemistry and mash pH end of brewing with decent results so far. I have been using the test strips with a margin for error large enough that it's really tough to see the true results of my water ion tinkering. I am actually leaning toward this one.
It has a read-out to .01 pH, but it does look like you have to do a 2 point calibration. From what I have read, the margin for error is a little narrower (but not a whole lot) than the test strips. But it least it operates in a larger range and provides a closer resolution than the strips. Certainly worth $40 new.
It also lists an operating range up to 122F, which makes me think I could easily draw a sample of my mash and bring it to an acceptable temperature quickly for testing.
How does calibration work? Do you have to do it every time you use it? It looks like those packets of calibration solution could get expensive if you had to use 2 every time you brewed
It has a read-out to .01 pH, but it does look like you have to do a 2 point calibration. From what I have read, the margin for error is a little narrower (but not a whole lot) than the test strips. But it least it operates in a larger range and provides a closer resolution than the strips. Certainly worth $40 new.
It also lists an operating range up to 122F, which makes me think I could easily draw a sample of my mash and bring it to an acceptable temperature quickly for testing.
How does calibration work? Do you have to do it every time you use it? It looks like those packets of calibration solution could get expensive if you had to use 2 every time you brewed
Hermit
fuddle
I like the $26 in accessory fluids to make your $40 meter last longer. I was checking some out on ebay that come with bottles of calibration fluid. Not sure about the cleaning, storage solution. Not sure the storage solution is different than the 7.01 calibration fluid from the write up.
remilard
Well-Known Member
There are a number of reasons not to measure mash pH at 122. One is that pH is always reported in the literature at reference temperature, the other is that it will wreck your probe much faster.
The phep5 is around $80 and works well for me (though I am thinking of upgrading). Morebeer sells that one and a more robust milwaukee meter at around $120.
Calibration solution as one time use powder packets is fairly cheap.
It should certainly be better than the strips. A meter that can measure temperature to better than 0.5°C and voltage to better than 0.5 mV is capable of accuracy of about 0.02 pH when used in a 2 point calibration with buffers which are good to ±0.02 pH (as are most of the technical NIST tied buffers sold). The strips generally have patches separated by 0.3 pH and are reported to be biased by 0.3 pH.
It varies a bit from meter to meter but in general you put the meter in cal mode, rinse the storage solution off the electrode and blot, stick it in one of the buffers and wait for the meter to beep at which time you rinse and blot again and then go into the second buffer, wait until it beeps, then indicate that you are only doing a 2 buffer cal at which point the meter tells you the slope and offset of the electrode and asks if you want to accept the cal. You press a key to tell it you do and you are ready to roll. Note: most modern meters can tell which buffer you are in. Some may ask you to enter the pH of the buffer.
Calibration should be done each day you use the meter. I was absolutely floored when a relatively new electrode I bought held cal for 2 months! Don't count on that.
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winvarin
Well-Known Member
Thanks AJ. Did you happen to follow the link I posted as to the meter I am considering? Would you consider that a good "starter" meter? You've not steered me wrong so far. I would be interested in your impression of that meter.
Does anyone know the pros/cons of the non-glass ISFET sensor vs. the traditional glass one?
The only "cheapie" I know anything about is the Hanna phep-5. For the price I am pretty impressed with that unit as it has ATC, automatic buffer recognition etc.
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winvarin
Well-Known Member
If I read the specs on that correctly, the thermometer function only goes up to 140F. Does that mean you'd still need to pull a portion of your mash out and let it cool below sacc temp in order to get an accurate reading from the meter?
I think several people have already pointed out that whenever pH is given it is understood that it was measured at laboratory temperature unless otherwise noted. If you keep intend to keep records of what pH you realize at particular points in the process you will want to be sure they are all recorded at the same temperature. Now a couple of degrees doesn't make that much difference. If we accept the nominal 0.2 shift for wort between room and mash temperature that amounts to 0.005 pH/°C. A 5° C (9 °F) difference in reading temperature would translate to about 0.025 pH which is about the accuracy of the meter (assuming a calibration with fresh buffers). Of course that's an additional 0.025 pH error you wouldn't have if you always wait until temp. is the same. I stick the sample in a small metal saucepan (very convenient for dipping out of the tun) and float that in a little cool water in the sink. When temp gets down to about 22-24°C I take the reading. I always note the reading and the temperature.
In addition all this, temperature cycling is stressful to the extremely thin glass bulb that actually measures pH so keeping things cool prolongs electrode life.
remilard
Well-Known Member
AJ, on the brewing network forums you pointed Kai to Hach for combo pH/DO meters.
I am thinking about taking a step up in pH meter quality and adding DO. Two questions about your experience with Hach.
Would you recommend their lower end portable meters or, if I am spending big bucks anyway, should I buy up a few models? This seems to be their entry level (for pH/DO).
http://www.hach.com/hc/search.produ...ekltWjNWbGMzUlZXbFpRV2pFeU9BPT1DRFl3TWpNeg==|
Second, am I missing something or are DO probes very expensive (2-3x pH probes). Do they last longer? At $570 a probe if they are as disposable as pH probes I might choose to upgrade to a better pH meter and just get a cheapy DO meter (as my accuracy needs in that department aren't as high as for pH, and I won't take as many measurements).
I am thinking about taking a step up in pH meter quality and adding DO. Two questions about your experience with Hach.
Would you recommend their lower end portable meters or, if I am spending big bucks anyway, should I buy up a few models? This seems to be their entry level (for pH/DO).
http://www.hach.com/hc/search.produ...ekltWjNWbGMzUlZXbFpRV2pFeU9BPT1DRFl3TWpNeg==|
Second, am I missing something or are DO probes very expensive (2-3x pH probes). Do they last longer? At $570 a probe if they are as disposable as pH probes I might choose to upgrade to a better pH meter and just get a cheapy DO meter (as my accuracy needs in that department aren't as high as for pH, and I won't take as many measurements).
The advantages are that you can store them dry, scrub them clean with a toothbrush and shove them into a pork picnic shoulder if you are interested in knowing the pH of the interior of a pork picnic shoulder (and people are). Based on this you would think they would last a good long time but in my, admittedly limited, experience they don't. I've had 2 and one crapped out within a year and I never was fully convinced the second was really working because it took forever to stabilize. I went back to glass (I don't care about the pH of a pork shoulder - only that it makes good sausage).
That is actually the meter I use in the brewery. It was the electrode that came with that meter that held its cal for 2 months which I mentioned earlier in this thread. I think it's a pretty good meter. It does the basic job, certainly, and has lots of nice bells and whistles. You don't actually have to write anything down as it stores everything in memory. You can transfer to a thumb drive and then your PC with all the details - what you measured when, what the temperature was, when the last cal was done...
This is a new technology (LDO) which makes use of and maintenance of the DO electrode lots simpler. You don't have to fill it, you don't have to polish the silver electrode, there is no membrane... The sensing element is a plastic cap which gets blasted with light from a LED and emits light of a different wavelength depending on how much O2 it is in contact with. The details of the calibration of this cap are stored in memory in the electrode itself. Now here's the catch - the cap only keeps it's cal for about a year at which time they want you to replace it (of course they do - they sell the things). And here's the good news - you don't have to because you can calibrate the meter each time you use it. Just put some DI water in a bottle, shake it up (to get the humidity in there to 100%), stick the probe in there and press Cal. Eventually I suppose the response will fall off and you won't be able to calibrate. I generally replace the cap every couple of years rather than every year.
One disadvantage with these is that as Hach is in the water treatment business the LDO probes are limited to 20 mg/L. Perhaps you could argue that one shouldn't oxygenate wort to or above that level but I do as a matter of course with my lagers. One can draw a sample, dilute it 1:1 with DI water and double the reading in such cases.
remilard
Well-Known Member
I see, you buy the very expensive LDO probe once and the cap is about $100 and is the consumable part. That seems more reasonable. I don't mind spending money for that part that should last me a long time (generally desire to upgrade gets me before things wear out).
Thanks.
