What Thermometer can i trust?

[cpbergie]

I currently have two thermomters. Your basic Thermoworks and a CDN Quicktip.

I calibrated the CDN in crushed ice with water and tested them both and they both read 32. Today I brewed and measured the mash temp, the Thermo read 156 and the CDN read 153. later when i tested the OG of the wort, i took another reading and the Thermo read 68 and the CDN 67.

I guess these aren't that far off, but im not sure which thermometer to trust and im not sure if i mashed at 153 or 156. I was really hoping to nail down my process and the temp of the mash seems to be a variable.

Any ideas or should I just RDWHAHB?

 

[david_42]

Ethanol and water boils at 172F at sea level and you're probably close. A much better calibration point for mashing.

 

[Skins_Brew]

get a lab thermometer. They are only $6 at my LHBS but its the only thing I trust anymore. I broke it the other day while transporting my brew gear, but at $6, its nothing I am going to loose any sleep over.

 

[zman]

I just got one of these at TJ Maxx for $13.00 http://www.oxo.com/OA_HTML/xxoxo_ib...=10062&item=75056&minisite=10024&respid=53057

I tested it in ice water and it was spot on.

 

[cpbergie]

Both of mine seemed spot on in ice water too. Are the floating thermometers as reliable as the lab thermometers? I have one of those.

I guess ill test them both again with boiling water. im only about 500 feet above sea level.

 

[jspence1]

I have three Taylor's They are almost perfect, I have one that reads 1 degree high and one that reads 1 low. I put all thee in ice water and brought it to a boil they stayed consistent through the entire time 0-212 with the other two reading 1 high and low across the entire range

 

[McCuckerson]

Ice bath temp should be 34F as it is changing phase.

 

[McCuckerson]

Ice bath temp should be 32F as it is changing phase.

 

[jmo88]

Ethanol and water boils at 172F at sea level and you're probably close. A much better calibration point for mashing.

+1. All of you ice calibrator folks should keep this in mind. Why focus the precision near freezing? Mash is at 150 or so. If you don't do ethanol and water, boiling water calibrations are still closer to intended mash temps.

 

[jamesnsw]

What mixture of ethanol and water would one use? Also, how would you figure in altitude to the 172°F?

 

[McCuckerson]

What mixture of ethanol and water would one use? Also, how would you figure in altitude to the 172°F?

and can you drink it after?

 

[jmo88]

What mixture of ethanol and water would one use? Also, how would you figure in altitude to the 172°F?

That's a good question. I calibrate with boiling water. But, I've read that ethanol, not a water mixture of it, boils at 172F. As for the mixture of ethanol and water, perhaps David_42 can chime in again.

 

[Scut_Monkey]

Both of mine seemed spot on in ice water too. Are the floating thermometers as reliable as the lab thermometers? I have one of those.

I guess ill test them both again with boiling water. im only about 500 feet above sea level.

I have found the floating thermometers to be extremely inaccurate. Mine reads at least 5 degrees wrong all the time and sometimes more. It's a useless piece of junk that screwed up many of my mashes until I realized this.

 

[cpbergie]

Thanks. And just for the record, I was calibrating at freezing because that was the only option for that particular thermometer.

 

[weirdboy]

That's a good question. I calibrate with boiling water. But, I've read that ethanol, not a water mixture of it, boils at 172F. As for the mixture of ethanol and water, perhaps David_42 can chime in again.

Basically what happens is the boiling point changes depending upon the concentration of ethanol in the water. That's how distillation works. Pure ethanol boils around 172F, but a mixture is going to boil at a higher temperature, and as it vaporizes that temperature will change.

 

[shek]

That's a good question. I calibrate with boiling water. But, I've read that ethanol, not a water mixture of it, boils at 172F. As for the mixture of ethanol and water, perhaps David_42 can chime in again.

I was actually curious about this so I dug around a bit. If you can get 192 proof, then it will boil at 172 deg F. If you're something less concentrated then the boiling point starts to rise, and eventually approaches 212 deg F with 0% alcohol. According to this:
http://www.biofuelvaportechnologies.com/files/Azeutruic_distillation_of_ethanol.pdf
I think you might be able to get away with cheap 80 proof vodka (40% alcohol by vol), which should have a boiling point of 183.2 deg F. However the boiling point will start to rise once the ethanol begins to boil away (bc/the concentration of alcohol will start to go down) so I'd guess that once you see bubbles, do your calibration quickly.

 

[david_42]

Here's a calculator for reduced pressure, but it's only good for water, pure alcohol and an azeotrope mix.

 

[The Pol]

That's a good question. I calibrate with boiling water. But, I've read that ethanol, not a water mixture of it, boils at 172F. As for the mixture of ethanol and water, perhaps David_42 can chime in again.

How do you calibrate at boiling?

How do you calibrate at 172F?

I have only seen thermometers that calibrate at 32F in a 60% slush 30% water meduim.

I am sure you can see how far off they are at say boiling or 172F, is that what you mean?

 

[The Pol]

Thanks. And just for the record, I was calibrating at freezing because that was the only option for that particular thermometer.

That is the only option I have seen for ANY thermometer... ?

 

[jeffmeh]

The expensive Thermapen allows for calibration at both 32F and 212F. But at close to $100, it should also be able to wash my car. :cross:

 

[The Pol]

The expensive Thermapen allows for calibration at both 32F and 212F. But at close to $100, it should also be able to wash my car. :cross:

So you can calibrate at 212? That is awesome, except wouldnt youd have to calibrate it at SLP too for it to be accurate??

 

[jeffmeh]

So you can calibrate at 212? That is awesome, except wouldnt youd have to calibrate it at SLP too for it to be accurate??

I am pretty close to sea level, lol. Actually, you can calculate the boiling point at your altitude, and calibrate it to that temperature. It has two calibration screws for using two reference points, but I do not know whether it would support using the upper one to calibrate somewhere around mash or hlt temperature.

I would expect it to be highly likely that if it is accurate at 32F and 212F then it would be accurate within that range, but it is certainly possible that there could be some variation.

 

[The Pol]

I know you can find #s for what temp you are boiling at, at your elevation (pressure)... but if I hit the calibration button and it calls it 212F and I am only boiling at 210F (due to elevation and pressure), then the calibration is 2F off.

I calibrate mine at 32F in a 60% ice 30% water slush, and at BOILING (not 212) they are .5F off.

 

[jmo88]

That is the only option I have seen for ANY thermometer... ?

This is the first I've heard that you can't calibrate at boiling. Why? I calibrated mine in a water and ice mixture and it showed I was boiling at 202F. So I calibrated it so I was showing boiling at 212F. I really don't understand the problem here.

 

[The Pol]

This is the first I've heard that you can't calibrate at boiling. Why? I calibrated mine in a water and ice mixture and it showed I was boiling at 202F. So I calibrated it so I was showing boiling at 212F. I really don't understand the problem here.

Are you using a digital?

The thermometers that I see most people using, when you push "calibrate" it sets that temp. to a constant. Typically 32F for a slush solution.

So if I place it in a glass of ice water press "calibrate" it calls that ice water 32F. I can place it in a glass of 40F water and press "calibrate" and it calls it 32F too.

If a Thermapen (mentioned above) calibrates at 32F and 212F... well, if my water is boiling on the stove, it isnt 212F... because I am not at sea level. SO if I place the thermometer in that boiling 210F water, press "calibrate", it will call that temp. 212F, which it is not. It is 2F off.

32F is not affected by pressure, so it is a pretty good #. 172F for the boiling of ethanol is great too, but wont work for a digital thermometer that most people use because you cannot calibrate to 172F

You are thinking analog, I am thinking digital

Simple.

 

[The Pol]

I am pretty close to sea level, lol. Actually, you can calculate the boiling point at your altitude, and calibrate it to that temperature. It has two calibration screws for using two reference points, but I do not know whether it would support using the upper one to calibrate somewhere around mash or hlt temperature.

I would expect it to be highly likely that if it is accurate at 32F and 212F then it would be accurate within that range, but it is certainly possible that there could be some variation.

Oh, so it calibrates at ANY temp? I dont get it. Do YOU choose the temp, or does it just calibrate at say 32 and 212?

If I boil at 209F, can I have it call MY boil 209F then?

 

[The Pol]

The expensive Thermapen allows for calibration at both 32F and 212F. But at close to $100, it should also be able to wash my car. :cross:

This is what confuses me...

Most thermometers with a calibrate with a push button. When you push that button, it calls whatever that temp. it is sensing, say 32F. I cant tell it to call it 40F.

So, if I boil at 209F, can I place it in a boil and calibrate it to 209F, or will it call it 212F?

EDIT: I have been trying to research how the Thermapen calibrates, and all I have found is that it uses a calibration trim button to fine tune at a single temp. (thier example was ice bath)

This may be useful if it is a TRIM, you could place it ina boil, if you know you boil at 209F, then trim the reading to that... that would work.

EDIT: That is how the Thermapen works, it has a ZERO and SPAN screw. Placed in ice water you adjust the ZERO trim to 32F. Placed in BOILING water you then adjust the SPAN to (212F) or whatever temp. your water boils.

I like the trim idea, that is nice. For $100 though, I will keep the ones I have as they are only off .5F at boiling and dead on 32F for $28

 

[jeffmeh]

This is what confuses me...

Most thermometers with a calibrate with a push button. When you push that button, it calls whatever that temp. it is sensing, say 32F. I cant tell it to call it 40F.

So, if I boil at 209F, can I place it in a boil and calibrate it to 209F, or will it call it 212F?

These have two calibration screws. Lets say that I know the water is at 209F. Then I would turn the upper range calibration screw until the digital display reads 209F.

 

[The Pol]

These have two calibration screws. Lets say that I know the water is at 209F. Then I would turn the upper range calibration screw until the digital display reads 209F.

Yah, see my edit above.

 

[jeffmeh]

I use the Thermapen in the kitchen, as I do not have the new splash proof model, and it started to get a little flaky when I was using it for brewing.

I ended up getting one of these http://www.thermoworks.com/products/handheld/mtc.html for brewing with their 113-372-T type K wire probe. I have been very happy with it, and there are a huge variety of type K probes available. On Thanksgiving, it was certainly much more accurate with the oil in the turkey fryer than the analog that came with it. The handheld will go up to 1999F, but the probe is only good to 482F, lol.