# Calibrating Your Thermometer and the Boiling Point of Water



## Dutch (May 31, 2012)

If anyone has ever questioned the accuracy of their thermometers, the first course of action that they are instructed to do is to calibrate their thermometers (if the thermometer can be calibrated). If your thermometer can't be calibrated, then you must compensate for the difference wither you use the Ice Bath method or the Boiling Water method

The two methods of calibration is the Ice Bath method in which the thermometer is calibrated to 32° F. (or 0°C). To me this method is the most accurate providing that you know the proper way to do the ice water calibration. No matter what your elevation is, water freezes at 32°F (0° C). Check here for the How To Make A Proper Ice Bath video. Thanks goes out to AustinL for posting that video link! 
	

	
	
		
		



		
			






The other method is the Boiling Water method in which you calibrate your thermometer to 212° F. (100°C). This method is great providing that you can calibrate said thermometer at sea level.  The higher you rise is elevation the lower you boiling temperature drops-also associated with the increase of elevation is the increase in the length of time it takes for water to boil. As for the length of time it takes-I'll let you all figure that one out for yourselves. 
	

	
	
		
		



		
		
	


	





Here is a chart that shows you the elevation and the corresponding boiling point. This chart shows both Feet & Meters and °F & °C. This Chart ranges from Sea level to 10,000 ft (3048 m) in 500 ft (152 m) increments.


Altitude compared to Sea Level

            Boiling Point 
 
_(ft)_

_(m)_

_([sup]o[/sup]F)_

_([sup]o[/sup]C)_

0

0

212.0

100.0

500

152

211.0

99.5

1000

305

210.1

98.9

1500

457

209.1

98.4

2000

610

208.1

97.8

2500

762

207.2

97.3

3000

914

206.2

96.8

3500

1067

205.3

96.3

4000

1219

204.3

95.7

4500

1372

203.4

95.2

5000

1524

202.4

94.7

5500

1676

201.5

94.2

6000

1829

200.6

93.6

6500

1981

199.6

93.1

7000

2134

198.7

92.6

7500

2286

197.8

92.1

8000

2438

196.9

91.6

8500

2591

196.0

91.1

9000

2743

195.0

90.6

9500

2896

194.1

90.1

10000

3048

193.2

89.6


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## forluvofsmoke (May 31, 2012)

Good info, Dutch.

Here's a similar water-boil chart that also shows barometric pressure, along with elevation from -500ft to 10,000ft, for the weather buffs who monitor a barometer closely...
Page Title:
*[font=Arial,Helvetica][size=+2]CALIBRATING THERMOMETERS IN BOILING WATER:[/size][/font]*​
*[font=Arial,Helvetica][size=+1]Boiling Point / Atmospheric Pressure / Altitude Tables[/size][/font]*​Web page written by:
*[font=Univers (W1)][size=-1]O. Peter Snyder, Jr., Ph.D.[/size][/font]*​*[font=Univers (W1)][size=-1]Hospitality Institute of Technology and Management[/size][/font]*​*[font=Univers (W1)][size=-1]670 Transfer Road, Suite 21A[/size][/font]*​
*[font=Univers (W1)][size=-1]St. Paul, Minnesota 55114 USA[/size][/font]*​Link: http://www.hi-tm.com/Documents/Calib-boil.html

*[size=-1]References[/size]*
[size=-1]1. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. 1997. ASHRAE Handbook - Fundamentals, Inch-Pound Edition. ASHRAE. Atlanta, GA.[/size]

[size=-1]2. Perry, R.H., Green, D.W., and Maloney, J.O. 1984. Chapter 6. Psychrometrics. Perry's Chemical Engineers' Handbook. McGraw Hill. New York, NY.[/size]
I did notice that the boiling points shown between these 2 charts are slightly varied, though this information was from literature dating back to 1997 and 1984 in the credits on the footer of the page.

Maybe science and technology has given more accuracy in the calculation formula nowadays...don't know...either chart gives a good idea what to expect for a boiling-point temp reading based on elevation/barometer reading, and that's the key point, bearing in mind that weather changes regarding high/low pressure systems also change barometric pressure, which is really what effects the boiling point of water.

Though I do not know what the time length change would be for a given measure of water to boil in a given vessel with a given btu input for a given elevation increase, I do know that slightly higher temps are needed to achieve the same relative cooking times for a given food...elevation (or more specifically, barometric pressure) does matter with cooking, as well as with thermometer calibration or verification.

Eric


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## chef jimmyj (May 31, 2012)

Great info...Thanks guys...JJ


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## kryinggame (Jun 1, 2012)

Thanks for this info. I've always had problems with the accuracy of digital thermometers.

I just bought the ET-732 and the probe judging the heat of my smoker is way off. My MES smoker can only get up to 275 degrees. Last weekend, I did a boston butt at 225 degrees; however, the ET-732 was reading at 298 degrees which is impossible.  I called the company and they're sending me a new probe.


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## bruno994 (Jun 1, 2012)

Great info guys.  Another reason this is where I spend 4 hours a day on this forum at work.  Keep up the good work.


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## figjam (Jun 1, 2012)

kryinggame said:


> Thanks for this info. I've always had problems with the accuracy of digital thermometers.
> 
> I just bought the ET-732 and the probe judging the heat of my smoker is way off. My MES smoker can only get up to 275 degrees. Last weekend, I did a boston butt at 225 degrees; however, the ET-732 was reading at 298 degrees which is impossible.  I called the company and they're sending me a new probe.


I recently got the ET-732 for a gift and it seemed to be reading about 10-15 degrees hotter than my smoker.  I haven't done the boiling point check yet, but I plan to.


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## garyz (Jul 10, 2012)

Interesting, forgot about elevation effects. Tested my cheapo digital from walmart ($8). read 209 boiling and figured I was 3f low. ordered a $50 thermometer (highly rated here). looks like when adjusting for elevation cheapo was only about 1f off!


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