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Old 07-23-2008, 07:53 PM   #1
killian
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Default thermometer calibration

I think I have read before that you should put a insulated cup with some ice in the refrigerator and then take the temp to check for 32 degrees and then check the temp for boiling water taking altitude in to account does this sound right? I have 3 thermometers and they all seem off and it is really not helping my process at all. any help here is appreciated.

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Old 07-23-2008, 09:16 PM   #2
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Alcohol boils at 172F, a very good checkpoint for brewing. Put some cheap vodka in a small pan (or a metal cup in a small pan). Heat slowly until the temperature stops increasing. This will occur when the alcohol starts boiling off at 172F. When all of the alcohol has boiled off, the temperature will start rising again until the water boils.

Everclear works even better.

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Old 07-23-2008, 11:30 PM   #3
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Quote:
Originally Posted by david_42 View Post
Alcohol boils at 172F, a very good checkpoint for brewing. Put some cheap vodka in a small pan (or a metal cup in a small pan). Heat slowly until the temperature stops increasing. This will occur when the alcohol starts boiling off at 172F. When all of the alcohol has boiled off, the temperature will start rising again until the water boils.

Everclear works even better.
VERY DANGEROUS !!!!!! Alcohol Vapor is flammable akin to gasoline vapor. If you insist on doing this get the video recorder out and tape it so your next of kin can send it to stupid human tricks
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Old 07-24-2008, 12:19 AM   #4
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The freezing point calibration should be done with a cup of crushed ice and water-- using just ice cubes won't work well.

You should also not mess around with boiling alcohol-- it's dangerous an unnecessary. Use boiling water as a calibration instead.

-Steve

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Old 07-24-2008, 12:39 AM   #5
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I did say "heat slowly", but some people can make anything dangerous.

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Old 07-24-2008, 01:15 AM   #6
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I would love to know what others do for temperature verification/calibration. I have what I consider several good instruments (thermometers of different sorts). These are not cheapo ones either yet they all differ considerably. I have some that are as much as 10 degrees off! That is huge for a mash temp you might be using it for. I even have an infrared gun and that thing is suppose to be plus or minus .2 degrees. Not even close..Best I can tell? That thing is off by more than 15; Plus it is so subjective to where you are pointing it and getting temps from. Best I see so far are the old school floating thermometers (alcohol based) that your LHBS sells. These seem to be the most consistent among each other. I'd love to pick 2 of my own thermometers that are dead on and just stick with those but I have no real way to tell. Every recipe you read talks about mash temps of 151 - 155 and I think the reality of anyone ever really accurately measuring that is slim.

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Old 07-24-2008, 02:48 AM   #7
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I have a floating thermometer and that is the one that I ended up going with when my probes were way out of wack.

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Old 07-24-2008, 03:43 AM   #8
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I use a digital probe-style thermometer and I've never had any problems with it. It has a calibration set screw and is accurate enough for me-- certainly within +- 1 deg. F. I calibrate it with ice water and boiling water.

I use a floating thermometer for checking wort temperature while it cools, so accuracy isn't critical. I've never checked it though, so perhaps I will now.

-Steve

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Old 07-24-2008, 01:24 PM   #9
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I was using a digital probe thermometer (the same one I cooked with) for the longest time until I bought a Ranco controller and it was reading 10 degrees less than the probe was. After that, I bought a 'laboratory' thermometer for the sensitive measurements (mash temp) and have been very happy with it.

My crappy probe thermometer also explains why all my steaks are overcooked.

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Old 07-24-2008, 04:46 PM   #10
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Quote:
Originally Posted by cwhill View Post
I even have an infrared gun and that thing is suppose to be plus or minus .2 degrees. Not even close..Best I can tell? That thing is off by more than 15; Plus it is so subjective to where you are pointing it and getting temps from.
Those IR guns are calibrated based on reflections off of black bodys(typically they are calibrated to 0.95). Essentially, the less reflective the object your measuring is the higher the value, 1 being max.

To correct for emissivity TempActual = (emissivityAssumed/emmisivityActual)^(1/4) * TempRead

Note: Temps are absolute(K)

Hope that helps.
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