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-   -   Digital thermometer accuracy (http://www.homebrewtalk.com/f11/digital-thermometer-accuracy-23431/)

Ol' Grog 02-28-2007 05:28 PM

Digital thermometer accuracy
 
I just got a digital thermometer and used it while steeping. Was curious about the accuracy so I put the probe in the boiling wort and low and behold, it only got as high as 210F. WTF???? I know it may have been off a degree or two, but 10? Or, does wort have a lower boiling temperature than that of plain water? Boy, if it is really off by 10F, I just screwed up my steeping grains. Mystery brew here I come.

david_42 02-28-2007 05:34 PM

Pure water boils at 212F at standard temperature and pressure. I think the thermometer is fine.

olllllo 02-28-2007 05:34 PM

Boil temp is affected by altitude and atmospheric conditions.

212°F at sea level.

ETA: As d42 stated, water purity.

EdWort 02-28-2007 05:37 PM

What's your elevation? While at sea level the boiling point of water is 212° Fahrenheit, for ever 500-foot increase in elevation, the boiling point drops one degree. Thus, at a city 5000 feet above sea level, water boils at 202°F.

I know where I live, I'm a little over 1,000 above sea level. My stuff boils at 210.

Here's some help on calculating your boiling point for where you live.

Ol' Grog 02-28-2007 05:44 PM

Wow. Didn't even think of that. Chickasha is 1093 above sea level, no global warming threats of oceans rising over HERE! So, anyway, that puts it about the same as Ed's, 210. And to think I was college educated and didn't figure that out for myself. Whew! That's good NEWS! No worry on the grain steeping.

todd_k 02-28-2007 05:49 PM

how do you find out how many feet above sea level you are? i googled richmond but couldn't find anything.

EdWort 02-28-2007 05:55 PM

Quote:

Originally Posted by todd_k
how do you find out how many feet above sea level you are? i googled richmond but couldn't find anything.

Richmond, VA is anywhere from 36 to 214 ft. elevation. If you are brewing on an overpass, your boiling point may be 211 degrees. :drunk:

abracadabra 02-28-2007 07:48 PM

After my floating thermometer broke I let the LHBS owner talk me into buying a calibration thermometer.

He was saying to check that against the dial themometer on my boil pot and showed me where to make the adjustment behind the dial gauge.

He also said the digital thermometer probably wasn't completely accurate either and to check it against the calibration thermometer and write down the variations in my brew books and then put the calibration thermometer up some place where it won't get broken.

Seems like the calibration thermometer was about $6

MA_Brewer 02-28-2007 08:02 PM

But what do you use to calibrate the calibration thermometer? :D

pjj2ba 02-28-2007 08:18 PM

I have two thermometers. One is designed for frothing of milk so it has a large easy to read scale conveniently centered around mash/sparge temperatures. I really don't need the scale to go up to 400 F. It can be adjusted/calibrated with a wrench. I finally bought this digital model specifically because it gave a rated accuracy (+/- 2F), which most thermometers don't, and it is easy to calibrate.
http://www.amazon.com/Taylor-9842-Professional-Waterproof-Thermometer/dp/B00009WE45

I always felt uneasy buying a thermometer that didn't give you any indication of how accurate it is.


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