Author Topic: Milwaukee pH meter issues  (Read 1781 times)

Offline redzim

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Milwaukee pH meter issues
« on: July 26, 2011, 07:29:55 AM »
Anyone with a Milwaukee MW102 or similar, have you experienced the following, which I have on the 4 or 5 mashes I've used this meter for(bought it in the spring):

I calibrate it with 7.01 and 4.01 solutions, Hanna brand (recommended to me by a Milwaukee tech on the phone) then test my sample at around 75F. The little hourglass shows on the screen for a minute or two, then disappears. I take my reading (in the case of an Oktoberfest this morning, 5.25.)  However as I stand and watch the meter, the pH climbs to 5.49 over 2 or 3 minutes, then stabilizes.... but this increase from 5.25 to 5.49 was all with the hourglass off. What is my correct reading?  Same thing happened with a Schwarzbier mash a few weeks back; the hourglass went off and the meter read 5.50, but it climbed up to 5.61 before it finally stabilized.

I know this is a bit nit-picky perhaps, because all the numbers are in a good range for the mash (this meter has ATC, but I always cool my samples into the 70s anyways) but I like to know what is going on.  I called Milwaukee and the tech was frankly not very helpful.  He said he thought the reading was valid when the hourglass went away, but  also said some drift in readings is unavoidable.  I am not stirring or shaking the sample, which he said is apparently a no-no, and I store the probe in Hanna storage solution all the time.... 

Any help from blatz, denny, or kai, or anyone else, would be appreciated....

thanks
Red

Offline glastctbrew

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Re: Milwaukee pH meter issues
« Reply #1 on: July 26, 2011, 07:55:44 AM »
I find it interesting that the tech told you not to stir the sample with the probe.  I use a pH56 and the manual states to gently stir the sample after submerging the probe.  I looked at the 102 manual and it states the same.

Regardless, I ignore the hour glass and wait for the reading to stabilize.
Scott
Still Hill Brewery

Offline narvin

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Re: Milwaukee pH meter issues
« Reply #2 on: July 26, 2011, 11:14:25 AM »
How do you store your probe?  I don't think it should take that long to stabilize if your probe is in good condition.
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Offline tom

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Re: Milwaukee pH meter issues
« Reply #3 on: July 26, 2011, 02:53:01 PM »
I have a Milwaukee SM102 and haven't seen that.  Maybe I don't watch it that long.
The actual pH will change with temperature (lower pH at higher temperatures - 0.35 difference between room temp and mash temp).  Is your sample still cooling while this is changing?  It sounds like more than I would expect.  I just write down the pH and the temp it was measured at.
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jaybeerman

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Re: Milwaukee pH meter issues
« Reply #4 on: July 26, 2011, 02:55:49 PM »
I had this exact issue with my MW101.  First of all I had a few discussions with martin B. and then I spoke with milwaukee.  Here's what milwaukee unofficially, store the probe overnight in 4.01 solution then rinse it off in the morning and put back into the storage solution.  I did that and then this is what martin suggested and I've yet to have the problem again.  cheers, j

"I rinse the probe like you do [distilled water], but I also blow the excess moisture off the probe by mouth.  [We both dry the outside of the probe with a soft cloth being careful to not touch the electrode]

You mention calibrating with 4 and then 7, but do you ever go back and check if there is some drift at the 4 point after trimming the 7 pot?  I find that I do have to check and retrim the pots to get my meter dialed in.  I find that it is an iterative procedure to calibrate.

I don't think you want to keep the probe in distilled water.  That might be bad for the probe. [i was calibrating the morning of the brew and then leaving the probe in distilled water untill mid morning when i needed it for the mash] You need to keep it in the storage solution and rinse it off prior to measurement.  Maybe its not such a big deal since you normally store the probe in solution.


« Last Edit: July 26, 2011, 02:58:37 PM by jaybeerman »

Offline thcipriani

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Re: Milwaukee pH meter issues
« Reply #5 on: July 28, 2011, 10:00:14 PM »
I actually emailed Kai this question about a year ago - hopefully he won't mind me sharing his answer in full here:
Quote
I just used the meter and what you are seeing is normal. You need to swirl the probe around to get a stable reading. In a lab you would put the sample on a small stirrer.

The probe acts like an acid itself and changes the pH in its vicinity. That's why you have to keep it moving a bit to  disturb the layer of changed pH solution that formed around the probe.
Tyler Cipriani
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Offline redzim

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Re: Milwaukee pH meter issues
« Reply #6 on: July 29, 2011, 06:05:23 AM »
OK so you basically ignore the hourglass, and swirl a little until the reading stabilizes?   I'll try that....

Online Thirsty_Monk

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Re: Milwaukee pH meter issues
« Reply #7 on: July 30, 2011, 06:25:25 PM »
I actually emailed Kai this question about a year ago - hopefully he won't mind me sharing his answer in full here:
Quote
I just used the meter and what you are seeing is normal. You need to swirl the probe around to get a stable reading. In a lab you would put the sample on a small stirrer.

The probe acts like an acid itself and changes the pH in its vicinity. That's why you have to keep it moving a bit to  disturb the layer of changed pH solution that formed around the probe.
Thanks for the info.
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