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Old 11-05-2012, 01:41 AM   #11
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Quote:
Originally Posted by ajdelange View Post
There is an easy way to check and that is to read the buffers after calibration as if they were samples. You should get a stable reading close to what is on the pH package label for the temperature of the buffer. See the Sticky on pH Calibration for details.
Yes, that's what I was doing today, and they (sometimes) seemed to read just fine. So I thought I could calibrate, and recheck the buffers, take the wort reading, and then recheck the buffer solution. I was hoping some smart person could say, "The pH of 5% white vinegar is 2.54" or something so I could see if I'm in the ballpark. I'm always looking for the easy way!

I've read the pH calibration sticky more than twice, just today.

Thank you so much for your help. I'll look at the meter tomorrow with a magnifying glass.
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Old 11-05-2012, 03:37 AM   #12
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Forgive my late night math if this is wrong, but the best I can do for what you probably have laying around would be phosphoric acid. The pH of 10% (1.1 M) H3PO4 is about 1.07. Diluted 9:1 (90 ml distilled water to 10 ml 10% H3PO4) is about 1.61.

It's certainly well outside your calibration buffers but it might be a fun test. If your slope is whacky this should show it.

 
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Old 11-05-2012, 12:13 PM   #13
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Speaking of phosphates, many brewers do have a phosphate buffer on hand in the form of 5 Star 5.2. It actually buffers to [Edit] 5.82 in distilled water as I recall but it is a buffer.

If I do the phosphoric acid calculations I come up with similar numbers varying a bit depending on whether I take ionic strength into account or not. But calculated values and measurements tend to differ as the low end of the pH scale is approached because of uncertainties about activity coefficients (I used the modified Debye-Huckle model which has been said to be accurate for slightly contaminated distilled water).

 
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Old 11-05-2012, 01:08 PM   #14
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I have phosphoric acid on hand, and various other things. When I get a chance to play around with it, I'll play mad scientist and see what happens.

I'm planning on brewing on Wednesday, so maybe that will be "mad scientist" day.
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Old 11-05-2012, 01:16 PM   #15
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Also maybe making sure an air bubble isn't trapped in the tube before the sensor.

 
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Old 11-05-2012, 11:27 PM   #16
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Seems like kaiser had this problem also http://www.homebrewtalk.com/f11/buyi...-meter-127062/ I know you said a new meter is out of the question but he seems to have switched to a manual calibrating meter instead of an automatic one. I didn't read the whole article yet but I'm sure there has to be at least a little info in that thread to help you

 
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Old 11-06-2012, 12:05 AM   #17
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Have tried doing a 2 point calibration starting with a 7.01 buffer?
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Old 11-07-2012, 09:24 PM   #18
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Quote:
Originally Posted by helibrewer View Post
Have tried doing a 2 point calibration starting with a 7.01 buffer?
Me? Always. That's the first buffer I use.

I talked to Milwaukee Instruments today, and the asked me to send in the meter again. It just would NOT calibrate today. It eventually said "ok" after "wrong" on the 4.01 buffer, but it drifted badly.

This will be about $12 just on postage sending it back and forth. I realize that's not much, but added to the cost of the meter and the new buffers because I thought it was an issue possibly with the buffer solution, and fresh electrode cleaning solution, I'm in over $125.
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Old 11-07-2012, 09:36 PM   #19
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A real incontinence but not bad customer service. It might be worth asking if an upgrade at a reasonable free to the MW102 based on the poor performance of your current unit is an option...

Sounds like you'll get a new unit anyway you go.

 
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Old 11-07-2012, 10:42 PM   #20
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Quote:
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A real incontinence ...
Oh dear, I hope not!

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