How important is thermometer accuracy really??

[punk_rockin2001]

Over the last 3 days I've become slightly obsessed w/my thermometers for some reason and have read waaaayyyyyy too much about them. I've read all about Thermapens, CDN proaccurates, flukes, taylors, thermistors, thermocouples, probe speed, traceability, accuracy, repeatabilty, etc.

Then I started to think that the only places that temp is really critical is sparge temp, mash temp, and fermentation temp. Now any decent thermometer will have an accuracy of +or- 2 degrees, and the more expensive ones have slightly better specs. So in a worst case scenario my thermometer is reading 152 instead of 150 in my mash..... so what?!?! I don't measure my water down to the ml, and I don't measure my grain out to the tenths of oz, and when I hop the more the merrier! I don't ask my yeasts exactly how many billion cells are present, or send my hops out to make sure they have exactly 7.8578% AA.

So after much deliberation I've decided its time to just sit back and have a home brew. With all things considered I just don't think worrying about whether the decimal point on my temp reading is correct, is worth the effort.

Edit: Do you agree that being within a temp range of +/-2 degrees is just fine for beer?

 

[motobrewer]

ok

 

[mcaple1]

Ok...then do this....since I can only assume some dial thermos have a +/- 5 deg diff at their worst, brew two batches....one mashed at 147, the other at 152. If there is no difference, then hey, guess thermo accuracy isn't important. However, if repeatability and consistent results are your thing.....you might want to take temp a bit more seriously.

 

[day_trippr]

ok

+1

 

[punk_rockin2001]

Ok...then do this....since I can only assume some dial thermos have a +/- 5 deg diff at their worst, brew two batches....one mashed at 147, the other at 152. If there is no difference, then hey, guess thermo accuracy isn't important. However, if repeatability and consistent results are your thing.....you might want to take temp a bit more seriously.

I'll agree there. I've only been researching digital though, and +/-2 seems to be pretty standard. But I wouldn't even mess with a thermometer if I thought it could be 5 degrees up or down!

 

[punk_rockin2001]

Ok, I see my post didn't actually get to the point I was hoping to ask.... is it generally accepted in brewing that an accuracy of +/-2 degrees is actually just fine?

 

[motobrewer]

Ok, I see my post didn't actually get to the point I was hoping to ask.... is it generally accepted in brewing that an accuracy of +/-2 degrees is actually just fine?

no

 

[mcaple1]

yes

 

[KNOTSANE]

I periodically calibrate my thermo's and trust the reading to be accurate. I have never had an issue. If I'm 2 degrees either way I sure can't tell in the final product.

 

[Junkster]

When I had just one thermometer, I always knew what temperature I was dealing with. Now that I have several, I don't know what the temperature is! <G>

 

[bernerbrau]

Thermapen.

 

[ajf]

From Greg Noonan (New Brewing Lager Beer) discussing the saccharification rest.

"The temperature of the rest may be from 149 to 160 degrees F (65 to 71 degrees C), depending on the nature of the beer being brewed. Precisely hitting the appropriate rest temperature is essential, as a variation of two or three degrees for even five minutes will dramatically alter the maltose/dextrin ratio of the extract."

-a.

 

[bad67z]

I was listening to a Q&A podcast on the BN, they cover a similar question. Jamil and John both agreed that you could have them professionally calibrated or do the old ice water and boiling water home calibration. But more importantly IMHO made a couple of good points:

1. Did the way your beer turned out at the temperature you mashed on your system?

If no: then adjust your mash temp +/- to get the desired character.

If yes:use same mash temp/schedule the next time

2. They pointed out that all of our brewing equipment differs from the others even thermometers. Brew to your system and make adjustments accordingly.

 

[mcaple1]

From Greg Noonan (New Brewing Lager Beer) discussing the saccharification rest.

"The temperature of the rest may be from 149 to 160 degrees F (65 to 71 degrees C), depending on the nature of the beer being brewed. Precisely hitting the appropriate rest temperature is essential, as a variation of two or three degrees for even five minutes will dramatically alter the maltose/dextrin ratio of the extract."

-a.

dramatically huh....dramatic enough that you honestly could admit you would be able to tell the difference between a beer mashed at 148 and 150. I really doubt that.

 

[RM-MN]

dramatically huh....dramatic enough that you honestly could admit you would be able to tell the difference between a beer mashed at 148 and 150. I really doubt that.

I've noticed the difference between otherwise identical beers mashed at 148 and 152 and decided that I don't particularly care for the one mashed at 148. I have since recalibrated my mashing thermometer to eliminate that error. Yes I know my difference was 4 degrees and not the 2 that was originally discussed.:rockin:

 

[ajf]

I just quoted from the book.
I've never tried mashing at 148, but I can certainly tell the difference between 150 and 152 when brewing my house ale; and I can tell the difference between mashing at 1 qt / lb, and mashing at 1.25 qt / lb

-a.

 

[mcaple1]

this kind of reminds me of when hardcore bud light drinkers cant pass a blind taste test between bud light miller light and coors light. I'm not completely doubting you, but in your situation, you KNEW that you mashed low, and I bet you were subconsciously EXPECTING it to taste different....in that case...I would love to brew two beers...a simple pale ale...and mash one at 148 and one at 154 (see, I made the spread even worse) and see if anyone can really detect a difference.

 

[motobrewer]

yikes. if you think there's no difference between 148 and 154, why even use a thermometer?

 

[RM-MN]

this kind of reminds me of when hardcore bud light drinkers cant pass a blind taste test between bud light miller light and coors light. I'm not completely doubting you, but in your situation, you KNEW that you mashed low, and I bet you were subconsciously EXPECTING it to taste different....in that case...I would love to brew two beers...a simple pale ale...and mash one at 148 and one at 154 (see, I made the spread even worse) and see if anyone can really detect a difference.

No, in my case I was wondering why this batch tastes so much worse than the previous which was one of my favorites. I checked over the recipe and thought about what I might have done differently and couldn't find any difference. It wasn't until 5 batches later I compared my mashing thermometer with my two digitals and discovered the discrepancy. Mine was a cream ale with oatmeal for heading.

 

[KNOTSANE]

I believe we are all missing the point here. WE are homebrewers enjoying a great hobby and are rewarded with the fruits of our labor. 1 in 100 home brewers probably have the equipment and set up to hit temps inside of 2 degrees on a consistent basis. I am not one of them but all my beers come out great and I try to learn something from each brew session. Those with automated systems that can keep a temp on point may be the one's expressing the necessity of dead on temps. Do you like the beer you brew? Well until we all get a setup that can duplicate our brews each time to a T then we will have to like the beer we currently brew. One day I will have an automated system and then maybe I will retract my opinion on a degree or two.

 

[Rivenin]

my thermometers are all about 2ish off, bought some i can finally recalibrate, so i do that, and its about as close as i can get.
as long as i hit my temps within 2*, i'm happy, but honestly, i prolly couldn't tell the diff if i tried to mash at 155* vs 152, all i know is if i want a drier beer, i go to the other side, if i go to the higher side, it gets sweeter

 

[punk_rockin2001]

I think the most eye opening part of everything I've been reading, is how inaccurate most thermometers actually are. I doubt most people realize it. Even thermometers upwards of $1000 still have to be professionally calibrated regularly. And there are basically NO exceptions. No, not even the super-hyped thermapen!... but that doesn't make me not want one.

 

[mcaple1]

I have checked the thermapen I have for calibration several times over a one year period. I have never had to recalibrate......NEVER. Now with that said....I'm not saying I never will....but damn is this trustworthy.

 

[bdjohns1]

I think the most eye opening part of everything I've been reading, is how inaccurate most thermometers actually are. I doubt most people realize it. Even thermometers upwards of $1000 still have to be professionally calibrated regularly. And there are basically NO exceptions. No, not even the super-hyped thermapen!... but that doesn't make me not want one.

Here's a perspective - part of my day job is developing protocols for accuracy of measurement systems used on a cheese plant. Every critical measurement thermometer is validated versus a NIST-traceable reference at least monthly. We generally don't accept error >1 degree, and for food safety, it always has to read higher (ie, tolerance versus the traceable reference is -0 +1).

 

[punk_rockin2001]

Here's a perspective - part of my day job is developing protocols for accuracy of measurement systems used on a cheese plant. Every critical measurement thermometer is validated versus a NIST-traceable reference at least monthly. We generally don't accept error >1 degree, and for food safety, it always has to read higher (ie, tolerance versus the traceable reference is -0 +1).

Excuse my ignorance (too much homebrew??) but I don't really understand your post. The thermometers at your workplace must read higher than the NIST-traceable thermometer?

Also a person like you deals with very high end temp reading tools daily, what do you use for your homebrewing?

 

[RM-MN]

Excuse my ignorance (too much homebrew??) but I don't really understand your post. The thermometers at your workplace must read higher than the NIST-traceable thermometer?

Also a person like you deals with very high end temp reading tools daily, what do you use for your homebrewing?

He probably uses his thumb to estimate the temperature of his mash.

 

[bdjohns1]

Excuse my ignorance (too much homebrew??) but I don't really understand your post. The thermometers at your workplace must read higher than the NIST-traceable thermometer?

Also a person like you deals with very high end temp reading tools daily, what do you use for your homebrewing?

For food safety, yes. Generally, we calibrate the devices to read 0.1-0.2 degrees high if they're digital.

He probably uses his thumb to estimate the temperature of his mash.

Nah, I just eyeball it. I have a calibrated eyeball

In all seriousness, there's still a lot of art going on. One of my best cheese-related stories was when I was working with one of our plants that was having yield problems (like mash efficiency in brewing-speak). No one could figure it out until we brought in the head cheese maker at one of our other plants. He watched he operator run a few vats, then said "let the tank agitator run backwards another 3 or 4 turns at the end of the tank fill". It worked. Everything else was being done to spec, but he could tell that there was still milk moving in the tank when it was supposed to be turning into curd.

At the end of the day, your system is only as accurate as your least accurate measurements/controls.

 

[Guess42]

I'd be interested to see a professional brewers take on how accurate they need to be on mash temperature.

 

[punk_rockin2001]

i'd be interested to see a professional brewers take on how accurate they need to be on mash temperature.

+1

 

[benzy4010]

Are thermapens really that great? I think I want one I dunno much bout it