The moment you realize your thermometer is broken....

Did a batch of Kolsch for an upcoming contest, and ended up a full point lower thant my estimated OG...ok I figured I must have made a mistake somewhere, but it'll be a session beer rather than a comp entry..Last weekend made a second batch of a saison recipe I've been working on..AGAIN much lower OG than my estimate..so did a calibration test on ye olde thermometer..and it was not just a few degree off..but like 15-20 degrees...sad panda here...

exhumedatbirth said:

Did a batch of Kolsch for an upcoming contest, and ended up a full point lower thant my estimated OG...ok I figured I must have made a mistake somewhere, but it'll be a session beer rather than a comp entry..Last weekend made a second batch of a saison recipe I've been working on..AGAIN much lower OG than my estimate..so did a calibration test on ye olde thermometer..and it was not just a few degree off..but like 15-20 degrees...sad panda here...

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I have suspected problems with my equipment and tested them as you have. Sadly, my equipment is perfect. It's my brewing that needs fixing!

I thought it could have been my brewing after the Kolsch failure...after the Saison where I was insane about the details I knew something was up with the temps...now I'm still going to drink these beers...and enjoy them..much like I'm enjoying the 2% lager I made when I forgot to shut off my HLT once the boil kettle was full...

I just discovered my thermometer was off too, by about 15-20 F as well. I've been wondering why my numbers were off and the beers were sweet, I'd been mashing WAY too high. Out to get a new one. (fingers crossed)

Haha...I just finished fiddling w/ 4 thermometers...maybe they are all wrong by the same variance. I like having at least two sitting on the counter next to each other...I read both as a check occasionally.

Ordered a digital stick recently direct ship from china on ebay...it reads a few tenths low in my estimation but not bad at like $3.89 to the door.

I also have experienced this problem....ruined an Oktoberfest! I was sad!

Last weekend I learned my bimetal thermometer was off by about 10 degrees too hot. I normally use my glass thermomter, but this time I used this other one. Luckily I checked before the mash in or I would have had 140F water instead of 150F.

What do you use to "check" the thermometer? If you use freezing and boiling you only have 2 setpoints. Not sure if a thermometer is going to be "off" a consistent amount across the entire temp spectrum. To the smarter people here: would a liquid filled thermometer (such as mercury or red alcohol) be more reliable for calibrating electronic thermometers? I would not risk putting a glass thermometer in my beer, but calibration is a different story. I have a thermopen oven thermometer, 3 bimetallic thermometers and a Taylor oven thermometer. Learned that the Taylor is junk, and the others are pretty much consistent with each other. Doesn't mean ANY are correct, but I'm hitting my target OG so I assume I'm OK.

I do not like digital thermometers. I've had several and the temps would jump around. For example, I would measure a temp in a particular spot and the thermometer would read 155 degrees and the next moment it would read 145 degrees. It would never find a consistent temp. I went back to my original glass thermometer, you kmow, the one you get with your first ever homebrew kit. I tested it out at freezing and boiling and found that thermometer read 4 degrees hotter than it should at both ends. I have two set points, both off the same amount and I feel comfortable assuming my glass thermometer is consistantly off throughout the measured temperature ranges. Since switching I've been hitting my OG numbers more consistently and I can better predict if I'm going to have a dry beer or a beer with body.

I checked my thermometer by simply reading it in the mash, then using a 'known good' glass thermometer. I usually stick the glass thermometer in the mash and 'stir' it around while watching the temp. If it jumps up in one area, I stir the mash to try to normalize the temp.

Glass thermometers are far more accurate and can be used to calibrate electronic ones. All you need are two points of freezing and boiling water to calibrate a glass thermometer since its response is linear in that range. If it is off from the markings it will be consistently off so you can come up with an offset that you add/subract from the reading to get actually temp.

Many bimetallics tend not to be all that sensitive, most I've seen I'd trust to give me a temp of +/- 5° actual. Which is fine for your oven or grill where that discrepancy doesn't make too big a difference.

For IR and electronic thermometers, you tend to get what you pay for, actually sometimes the cheaper ones aren't worth the battery used to power them.

What's that saying..."A man with one thermometer knows what temp it is. A man with two is never sure."

A solid solution:
https://www.homebrewtalk.com/f16/thermopen-refurb-69-99-a-342119/

This is what I use now, so far it's been super accurate withing .001 of my target OG...now if my first batch with the new thermometer did not get a nasty infection!!! figures it was a comp beer.

http://www.amazon.com/gp/product/B002GE2XF8/?tag=skimlinks_replacement-20

Remember that you should calibrate your work themometer to a reference standard thermometer in the temperature range you are most interested in. For mashing, try and calibrate somewhere in that 140F to 160F range in order to reduce the error. I prefer a NIST-certified mercury thermometer for my reference standard thermometer. I calibrate all my thermocouples and dial thermometers to that standard in a hot water bath in an insulated container.

I've seen some thermometers be several degrees off at 150F even though they seemed to correctly measure 32F and 212F in the freezing/boiling test.

Every homebrew club should have a good reference thermometer so that they can get together and have a thermometer calibration party a few times a year. You need an excuse to drink, don't you?