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Thermometers a plenty... accuracy?

I have three thermometers (2 dial, 1 floating) that I have collected over my very short brewing career. To date I have been an extract brewer and was getting into my first partial mash batch (surly bender). Before I started to heat any kind of water I wanted make sure my thermometers were calibrated. I put all 3 into a glass of water filled with ice. All thermometers gave different temps. What it the best way to calibrate thermometers? Are digital one more accurate?

put them in ice and then check again at boiling. i have one that is right on at both temps but its off at 150 :shock:

I was in a similar situation. I have about 3 different thermometers that I typically use on a brew day but had no idea how accurate they were at brewing temps. After reading some info on here I realized that checking them at freezing and at boiling doesn’t really help me when most critical brewing temps are in the 140 to 160 range. I posted about it and got a lot of advice and suggestions and ended up purchasing a fairly inexpensive certified and traceable calibrated digital thermometer. This helped me discover that in brewing temp ranges my current thermometers were as much as 5 degrees off on the high side.

Check out the thread here…

http://forum.northernbrewer.com/viewtopic.php?f=5&t=105820

Just remember that if you are checking at boiling you have to take into account your elevation and current barometric pressure.

http://www.thermoworks.com/software/bpcalc.html

crushed ice with a bit of water is the most accurate way to test them, they should read just above freezing. The floating one you can’t adjust, so remember how much it’s off if it is. Good bi-metallic instant read thermos have a adjustment nut under the head, often the plastic sleeve it lives in has a hole and groove at the end for adjustments. If yours doesn’t have such a sleeve but does have the nut just use an adjustable wrench to hold it while you turn the head to the correct the temp. Check it once a month to be sure.

dob

[quote=“speed”]put them in ice and then check again at boiling. i have one that is right on at both temps but its off at 150 :shock: [/quote]Me too. The one I always use seems to be off by 5 degrees at 150F

I made the mistake of calibrating mine with freezing water. I was off 8° in the 150ish range. Ended up mashing at 161°. Oops. I bought a couple digital thermometers and just calibrate my dials with those at roughly my mash temp.

Get a “Traceable” thermometer…

Yep, I now have 2 dials, 3 lab thermos and a digital that are all off and unreliable. I know I’ve mentioned this but I broke down and got a Thermapen. It’s always accurate and I can measure my mash temp with confidence.

How do you know it is always accurate without a lab certified reference thermometer to measure it against? I have considered a thermapen, but my daughter who is in a lab (and heading to grad school next year) said I would get just as accurate readings using my floating alcohol based thermometer, digital cheapo and the dial thermometer and averaging them. They are typically within 2 degrees of each other. I just checked my mash temp and the dial said 150, the floater said 150 and the digital (Accurite brand), said 151.5F. I think I can live with that differential, though the speed of the Thermopen is impressive.

:cheers:

How do you know it is always accurate without a lab certified reference thermometer to measure it against? I have considered a thermapen, but my daughter who is in a lab (and heading to grad school next year) said I would get just as accurate readings using my floating alcohol based thermometer, digital cheapo and the dial thermometer and averaging them. They are typically within 2 degrees of each other. I just checked my mash temp and the dial said 150, the floater said 150 and the digital (Accurite brand), said 151.5F. I think I can live with that differential, though the speed of the Thermopen is impressive.

:cheers: [/quote]
When I first got the Thermapen, I measured the temp of a glass of crushed ice and water and it fluttered between 32.1° and 32.2° depending on where I placed the probe. I have done this now a number of times and the reading is the same. What I occasionally do is use a dial/probe thermo in my mash or strike water and then as it comes to 160° (or whatever) I measure it with the Thermapen and it’s usually around 3-4° different. I calibrate the dial/probe jobbies but they just don’t seem to stay right. I will also do this with glass lab thermos which seem better but I have three of those (different brands) and they don’t agree. That 3-4° could be the difference between 150 and 154° which could make a difference in your beer. Also, Thermapen allows you to return the unit for free calibration if you think it’s necessary. All of this is about confidence and I have confidence in the accuracy of this device. I can’t say that about the probes or lab thermos. Also, I had a cheapie digital when I first started AG. It would bounce all over the place within a 10° range for like 60 seconds. It drove me crazy! Cheers.

Sounds like a good device, Ken, maybe I will suggest that my wife place a Christmas order… In any event I certainly can’t argue with your results - I have made a couple of your recipes and they were both well received and delicious in my opinion.

:cheers:

I agree with Ken after owning a Thermapen, I won’t be purchasing anymore cheap thermometers. It always accurate when checking at 32F and using Thermoworks boiling point calc taking into account for elevation and current barometric pressure its always on at boiling as well. If you feel that it needs to be recalibrated, Thermoworks prvides a great calibration service that offers NIST-Traceable certificates.

I also agree with getting a thermapen. I had two floating thermometers, a lab thermometer, and a dial unit which all read within a degree of each other at mash temperatures, but the thermapen was a big upgrade due to the fast settling time. And the one I got agreed with the others as well.

I was talking to one of the LHBS guys one time and he said that the standard dial/probe thermos (like a Miljoco) pretty much need to be calibrated each time you use it. What? Eventually I moved towards the glass lab thermos (which are crazy fragile) but even those are not accurate throughout the whole range of temps that a homebrewer might work in. I eventually got the Thermapen for overall convenience but the thing that got me was that my beer was coming out sweet. The beer was fully fermented and all of that but I was unknowingly mashing high. 150 was really 154 and 152 was really 156, etc. Many of the areas of my brewing are low-cost. My brewpot has no features like a spigot, sightglass, etc. It’s just a pot. My MT is a plastic cooler and I have an outdoor burner, immersion chiller, plastic fermenters, El-Cheapo plastic dial scale for my grains, etc. There are almost NO upgrades in my equipment so the Thermapen is an exception and an area where I think it’s warranted. Cheers.

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