Correct temperature effect on Specific gravity

Question

Correct temperature effect on Specific gravity

Mike Meyers

2018年5月16日 10:13

Is there an equation that corrects specific gravity while considering temperature effect in Celsius, which does not presupposes a set hydrometer calibration temperature?

A direct relation, not tables or something static. And if there is one, where would you find it?

A similar question was asked Here, but the answers are all in Fahrenheit or assume a 15 C (59 f) calibration temperature.

Topic specific-gravity calculations hydrometer temperature homebrew

Category Mac

Peter Cotton · Accepted Answer · 2018年5月16日 10:13

1

Peter Cotton answered at 2018年5月16日 10:13

I cool my wort to around 23 degC before taking a reading. Only takes a few minutes to cool a test tube from 100 degC to 23 degC

Martin · Accepted Answer · 2018年5月14日 06:41

It depends on the hydrometer. Older hydrometers tend to be calibrated at 15C (59F), and more recent ones at 20C (68F).

Yes, there has been some attempts to correct for an offset in temperature. Check out https://www.brewersfriend.com/hydrometer-temp/ for more details.

Anyways, I’d guide against measuring at a different than the calibrated or recommended temperature. This is because warm wort might shatter a glass hydrometer causing small metal balls to leak. I assume they are made from lead. Or even worse, it might crack the glass making it hard to discover. Additionally, in my personal experience measuring hot wort generally produce inaccurate readings even when trying compensate for the temperature.

Evil Zymurgist · Accepted Answer · 2018年5月13日 23:44

1

Evil Zymurgist answered at 2018年5月13日 23:44

It actually depends on the hydrometer. They can vary a lot beween makers. Each one has thier own temperature adjustment chart. Because they can have different displacements and scales on them.

Mr_road · Accepted Answer · 2018年5月12日 17:23

Quick but not very helpful answer, I am pretty sure there is some sort of equation that can be used for this I am not sure where I have seen it. I am going to do some digging through some book and the interwebs for you and will update here if/when I find it.

Found it, it assumes T is in C.

SG(true) = SG(indicated) x [ 1.0 - 0.00025[ T(actual) - T(calibrated) ]]

Correct temperature effect on Specific gravity

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