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Old 12-08-2010, 08:32 AM   #11
craigevo
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Reading the email reply from the supplier of the strips states "The sensitivity of the part
number is 0.2-0.3 pH units." implying that it could be plus or minus 0.3. Maybe Kai's batch just happened to read 0.3 low ?

So, this would suggest that you could be 0.6 out if you assume its reading 0.3 low, but the batch you happen to get actually read 0.3 high !

Anyone else compared these colorphast strips with pH meter ? I have just order some myself and would like to know if they are always minus 0.3 - if so then fine. If not then they are basically a waste of time right ?

On second thoughts, maybe the "sensitivity" quotes is actually referring to the graduation of the readings !


 
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Old 12-08-2010, 01:59 PM   #12
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Quote:
Originally Posted by craigevo View Post
Reading the email reply from the supplier of the strips states "The sensitivity of the part
number is 0.2-0.3 pH units." implying that it could be plus or minus 0.3. Maybe Kai's batch just happened to read 0.3 low ?

So, this would suggest that you could be 0.6 out if you assume its reading 0.3 low, but the batch you happen to get actually read 0.3 high !

Anyone else compared these colorphast strips with pH meter ? I have just order some myself and would like to know if they are always minus 0.3 - if so then fine. If not then they are basically a waste of time right ?

On second thoughts, maybe the "sensitivity" quotes is actually referring to the graduation of the readings !
IIRC, Kai gathered data from several people on the pH strips and conducted some experiments. It's probably posted somewhere on his Braukaiser.com site.
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Old 12-08-2010, 02:14 PM   #13
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He checked my ColorPhast strips, was the same as he had found on his own strips.
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Old 12-08-2010, 03:34 PM   #14
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Quote:
Originally Posted by craigevo View Post

Anyone else compared these colorphast strips with pH meter ?
Several people. They read, on average, .3-.4 units low for mashes (whether this is simply a function of being in that range or a physical feature of the mash, I do not know). This is true for several different packages of Colorphast strips purchased from different places at different times.

This is different from the fact that the points that you can read are far apart. So you have the issue that you can only tell the pH within a couple tenths because the resolution is poor and also that whatever you do read is .3-.4 low on average.

 
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Old 12-08-2010, 03:58 PM   #15
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IOW bias error, random error and lack of precision.

 
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Old 12-08-2010, 04:41 PM   #16
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My biggest hesitation to buy a decent $100 meter is the process of calibration, storage and ultimate probe replacement at regular intervals. This isn't a tire pressure gauge.
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Old 12-08-2010, 05:00 PM   #17
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Quote:
Originally Posted by Bobby_M View Post
My biggest hesitation to buy a decent $100 meter is the process of calibration, storage and ultimate probe replacement at regular intervals. This isn't a tire pressure gauge.
Meh, I bought a $30 one, with an $18 replacement probe. It's close enough to get me in the proper range for beer making. Unlike test strips, it at least tells me something.

 
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Old 12-08-2010, 05:01 PM   #18
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Quote:
Originally Posted by Bobby_M View Post
My biggest hesitation to buy a decent $100 meter is the process of calibration, storage and ultimate probe replacement at regular intervals. This isn't a tire pressure gauge.
I'm kind of hard-wired to "buy a good tool, buy it once." It's hard for me to accept that if I buy a pH meter, I'm basically going to have to buy it all over again within a few years. Even the meters with the replaceable electrodes, I've seen $70 meters where the replacement electrode is $50 or $55.

EDIT: A $30 tool that needs an $18 replacement, that I could live with. It may be psychological more than anything, but if I'm paying more than $50 for a tool I hate for it to be basically disposable.
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Old 12-08-2010, 05:03 PM   #19
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Correct me if i'm wrong..... After checking several styles of mashes and knowing what it takes to adjust them, constant ph checking shouldn't be necessary?

If so, it's not like you're going to be buying tons of replacement probes.

 
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Old 12-08-2010, 05:07 PM   #20
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... but if you HAVE a pH meter, why on earth wouldn't you use it on every batch just to check? Seems to me that would be like saying, "I've brewed this recipe a half-dozen times before, I'm not going to break out the refractomer/hydrometer this time." I mean, you'll likely be fine, likely be within the expected range, but why have the tool if you're not going to use it?

I'm also not sure whether the probes degrade over time (with or without use), or whether they only degrade when actually being used.
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