So I bought a laboratory thermometer from my LHBS last week and brewed a 10 gallon APA with columbus, cascade, simcoe and amarillo hops and split it into two 6 gallon carboys. One with 2 vials of white labs San Diego super yeast and the other with 2 vials of Dry English Ale. I was expecting an OG of 1.055 and ended up with 1.040. Come to find out my brand new “laboratory thermometer” is reading 235F at boiling and 131F at an actual temp of 150F. Let’s just say you don’t extract much at a 130F and the beer taste like grain water with some hop aroma. I go back to my LHBS and get a new “laboratory thermometer” today and its reading the same damn thing. Where can I get an accurate thermometer? I’m done ranting. Did I mention I calibrated all my thermistors on my brew system with this and now they’re all wrong.
Easy way to calibrate your thermometer is to add it to glass of water with a bunch of ice in it bc then You know bye putting it in the ice bath it should be 32 degrees bc that’s what the liquid is at and you can see how off your therm is off
We got a Thermopen on sale. Not cheap even on sale. I must say that is accurate and precise, from the data sheets (those are 2 different things of course). Also fast acting due to the small thermocouple junction mass. Really like it! And as an added bonus - we use it in cooking.
i would also check it at boiling and should be 212 (ish assuming standard atmospheric pressure) the case you describe being over reading by 19 degrees at 131 and by 23 degrees at (presumably) 212. i have used a digital probe used for cooking beef, candy etc with good success. they are not particularly expensive.
Wow, you could probably guess the temperature more accurately than that. What kind of thermometer was it? If it was high at boiling and low at freezing, then its more than just a simple adjustment.
A scientific supply company might be a better place to look. Here’s one, but there are many.
At mash temperature my NIST certified glass thermometer reads 7 to 8 degrees F below two Ranco probes, two dial Blickman thermometers, one handheld dial thermometer, and one nice digital model. Just to confuse the matter, I checked it against a glass NIST calibrated (cheap) lab thermometer, and it is all over the place. I need to do the calibration thing as well.
The trick with boiling water freezing water calibration, as the OP pointed out is that the temp range we are concerned with is neither. A thermo may read 235 at boiling but 28 at freezing. who knows what it’s like at mash temps.
The thermapen is great multiuse and “accurately precise” thermometer for a range of applications including cooking. Just don’t submerge it past the probe in the mash or there will be problems.
The thermopens that I have are water resistant. You can get water on them and they work fine. They are not, however, water-proof but I’ve never had the need to submerge one so it hasn’t been a problem.
I understand that previous models were not even water resistant and that would not be ideal.
After hearing all of the excellent reviews about the Thermapen, I finally ordered one and highly recommend it if you can afford it. It comes calibrated with a certificate and it’s traceable to a NIST standard. Well worth the money IMO. Super fast readings (3 seconds) and it’s very water resistant. Very accurate to ±0.7°F. It gets wet all the time with no problem. You can get one for about $80.
Did the ASTM ice bath calibration on the “good certified” thermometer and it reads 35.5F. The cheap one reads almost right on. The good news is Cynmar is shipping a new “good certified” one. Since both of these are partial immersion, I made sure I used the immersion mark for the test.
A quick search found multiple sources. Looks like they’re a bit more than a thermapen. Admittedly, I got mine as a gift from my last employer. Used it for 5+ years so far. Our club did a calibration demo. Mine was spot on at 32, 150 and 212.
