thermometer calibration

[killian]

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.

 

[david_42]

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.

 

[Tomfooleryxxx]

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

 

[SavageSteve]

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

 

[david_42]

I did say "heat slowly", but some people can make anything dangerous.

 

[cwhill]

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.

 

[killian]

I have a floating thermometer and that is the one that I ended up going with when my probes were way out of wack.

 

[SavageSteve]

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

 

[ajwillys]

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. :cross:

 

[jcb317]

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.

 

[T-Hops]

I use my alcohol thermometer to calibrate my dial thermometers once a month. Prior to buying the alcohol thermometer I was getting beer that was finishing very very low(1.005). I checked my thermometers with the alcohol one and my favorite thermometer was reading 6 degrees high. I would recommend buying an alcohol thermometer for calibration purposes. I would also calibrate my thermometers at mash temps not at freezing and boiling temps. Freezing and boiling temps mean nothing in brewing.

 

[killian]

I use my alcohol thermometer to calibrate my dial thermometers once a month. Prior to buying the alcohol thermometer I was getting beer that was finishing very very low(1.005). I checked my thermometers with the alcohol one and my favorite thermometer was reading 6 degrees high. I would recommend buying an alcohol thermometer for calibration purposes. I would also calibrate my thermometers at mash temps not at freezing and boiling temps. Freezing and boiling temps mean nothing in brewing.

I have a true brew floating thermometer how would I know if this is an alcohol thermometer or not?

 

[killian]

damn I think I need to buy something new - almost all of the thermometers I have are a little off, they read any where from 200 to 208. I had a digital one that was right on and once I started measuring my strike water it started turning off then on again. So I thought it must be the batteries and ran to the store once I changed the batteries it was still acting up. I just ended up using the 208 one and adjusting. How accurate can that be at mash temps

 

[jcarson83]

I did say "heat slowly", but some people can make anything dangerous.

I don't see a problem with that. Chefs do this all the time for different sauces and purposely light them on fire. Its not like your going to dump a fifth of everclear on and start boiling it. Or I guess there are some that might

 

[killian]

anyone using a weldless thermometer - any recommendations on a good one to buy?

 

[GilaMinumBeer]

Freezing and boiling temps mean nothing in brewing.

Boiling temps actually have a lot to do with brewing.

Unless you use some kind of baseline phenomenon for verification then how can you be assured that your lab thermometer is even correct? I mean, my floating thermometer is an alcohol based thermometer but, after the wax (or whatever it is) had melted and displaced it has been inaccurate by about 5*F.

Freezing and boiling temps at least give you a high and low limit baseline to verify accuracy against which is much more accurate than assuming that anything lab grade has kept it's tolerance over time.

 

[ChemE]

I think what T-Hops was getting at is precisely what I was thinking which is it is always best to calibrate an instrument in the middle of the range you intend to measure in. It would be ideal to calibrate a thermometer to 152F rather than 32F and 212F. Also, three point calibrations are better than two or one point.

And while boiling temperature does apply to homebrewing measuring and monitoring doesn't matter since a liquid is either boiling or not and therefore no measurement is required.

 

[killian]

I like to know when Im getting close to the boil so I can watch for boil overs.

 

[ajwillys]

I like to know when Im getting close to the boil so I can watch for boil overs.

Digital thermometers with the wireless pagers are fantastic for this. I can roam just about anywhere knowing the pager will go off when my water reaches 200.

 

[killian]

I use a digital but it is not wireless

 

[killian]

I have three digital therm's reading @ boil 208, 209, 212.
I have some kind of short in the one that is accurate and it keeps turning itself off.

 

[Boodlemania]

According to NIST, checking the zero point (i.e. ice slurry) is all that's necessary for recalibration of liquid-in-glass thermometers.

RTD's, like what are used in digital thermometers, are "essentially" linear devices within their operating range which only require offset correction (the trim pot adjustment mentioned earlier in this thread)

One word of caution (other than boiling alcohol), dial thermometers are notoriously inaccurate and non-linear at the ends of their travel (lowest temperatures and highest temperatures). They should only be trusted in the middle half of their scale.

 

[killian]

my floating thermometer reads 32 in an ice bath, 200 @ boiling
digital all read 32 - 33 in an ice bath

 

[david_42]

200F @ boiling says you have a serious problem, because there is nowhere in NY high enough for that to be correct.

 

[menschmaschine]

anyone using a weldless thermometer - any recommendations on a good one to buy?

This:
http://www.zymico.com/TT/

Plus this (#6092N-1):
http://www.taylorusa.com/foodsvc/thermo/bitherm.html

... are what I use. My thermometer almost never goes out of calibration. With any decent calibratable thermometer, 32dF in a cup of ice slurry is all you need. We're not NASA here. If I mash at 152.0 or 152.2, it isn't gonna make a big difference.

 

[killian]

that thermothingy says it will fit 1/8 to 1/4" how does it adjust from one size to the other?

 

[menschmaschine]

that thermothingy says it will fit 1/8 to 1/4" how does it adjust from one size to the other?

Lots of teflon tape! I use it with a 1/8" and have no problems with leaks at the thermometer. The T-fitting however was a real pain the ass to get onto a keggle. It didn't tighten all the way for me because the nipple has a slightly greater diameter in the center than at the ends. I ended up buying and using 2-3 extra SS washers on each side before it would tighten enough.

 

[killian]

Ok Im going to order a lab therm and I'm going to look for a remote digital therm. Is there anyplace to find a lab therm some where other than my lhbs?

 

[Boodlemania]

Cole Palmer, Omega. I would vote Omega over Cole Palmer though.

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