Measuring PH

[andrewb_1985]

Hello so I know there is lots of info on this but I have questions regarding my ph measuring equipment. First off I am new to AG brewing and am doing my first batch this Sunday. I chose to wait till today to play with my PH meter and try to figure it out. My meter is a EcoTestr PH2 with auto temp compensation.

Right out of the package it tested accurately in my ph4 and ph7 calibration solution at 70F. I took a sample of my tap water at 55F and it measured 7.7ph. Once warmed up to room temp, again 70F, the reading was 8.1. That seemed like a big jump to I warmed some water up on the stove to 145F (approx. mash temp) and reading was 8.8 and once again at a mash out temp of approx. 170F and reading was 9.1.

So my question is are these kind of fluctuations normal with tap water? or is my meters ATC not working? Also I have read that my wort ph at mash temp will be lower than at room temp. Is it normal for water to be the opposite?

I am simply trying to make sure I don't start off with faulty equipment and if anyone has any advise on how to measure ph correctly. It seems my meter is only accurate at exactly 70F... Thanks for your help.

 

[andrewb_1985]

I did also check the ph of the water warming up at several points between 70F and 140F. Ph rise seemed to be pretty linear.

 

[krahm]

You'll want to test your mash ph at room temp. Testing at mash temp will yield a different result, and it will potentially damage your meter (my understanding is that it will cause premature failure of the meter). So mash in, mix well, seal up the mash, wait ten minutes or so (but not too long; mash ph changes over time), then draw off a small sample and cool it to room temp. Then calibrate your meter with 7.0 solution, rinse it in distilled water, and measure your mash ph.

I did the same thing you did when I first got my ph meter. I, too, got wild fluctuations from tap water, but I think that's normal (not sure why; maybe a more knowledgeable source will chime in). The bright side is that you don't need to worry about it. If you get a constant reading with the calibrated unit in the calibration solutions, you're good to go. You'll find that you get consistent, reliable readings with the mash at room temp. It becomes second nature, and you'll stop stressing about it. You only need to worry when you get wandering readings in the calibration solution--that means your unit is failing.

'Hope that helps.

 

[kujosp]

ATC maintains calibration of the pro away from the normal temperature


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[kujosp]

*probe; ph(room temp)=ph(mash)+0.0055(tmash-troom) temps in Celsius. Equation from Water by Palmer and Kaminski


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[kujosp]

So the meter doesn't automatically adjust for temperature, it only maintains calibration with temperature fluctuations. The equation above can be used to adjust for pH based on temperature.


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