Thermometer accuracy

Hey all,

I picked up a thermometer (just a simple analog dial with a stainless stem. meant for cooking meat) for use when I do my next partial. It'll be a huge improvement over my previous method ("making the water just hotter than the point where you can't touch it" )

In any case, I am testing it in a glass of ice water, and it is registering at 2*C. Now if boiling water registers at 102*C do I just add 2 to every temp in between when I am mashing? (or if it comes out being say 105 for boiling, I would take the temp I want and multiply it by 1.03 to get the temp I see on thermometer)

Sorry if that was worded poorly! Essentially I am asking if I simply interpolate between what it reads for ice water and boiling water?

As an aside, does it matter if the ice water covers the entire stem of the thermometer? I might go try it again to see if that is the issue...

Most of these kinds of thermometers have a nut on the back around the stem. You can turn this nut a little to calibrate them.

However, I have never had one of these kinds of thermometers prove to be accurate over a large temp range. Granted, I have only ever had relatively cheap ones like this, but on the ones I have messed with.... if I calibrate them in ice water, they are off in boiling water. If I calibrate in boiling water, they are off in ice water.

Check yours in ice and a boil. If it's off a static amount, you can turn the nut to calibrate it and you'll be good to go. If it behaves like the ones I have, you'll have to decide for yourself how to interpret the readings.

Thanks Walker - it does indeed read off both temps. 2*C for ice water, 97*C for boiling. Shouldn't be too much of an issue hopefully - I'm going to convert all the *F to *C anyway, it'll just be an extra step.

In my opinion for all grain or partial mash brewing, I think a good, fast, accurate thermometer is one of the most important pieces of equipment you can have.

If your mash temp is off by 2 degrees in addition to the normal error range you'll get from your equipment and environment, that can make a HUGE impact on the final product.

All the meat thermometers I have like that say not to use them in water, not sure why but that might be a problem. I bought what seems like a nice thermometer online for $20, both the housing and the probe are fully submersible and the probe measures from -40 to 300 F. Should get here tomorrow or the day after, then I'll test it out.

In my opinion for all grain or partial mash brewing, I think a good, fast, accurate thermometer is one of the most important pieces of equipment you can have.

If your mash temp is off by 2 degrees in addition to the normal error range you'll get from your equipment and environment, that can make a HUGE impact on the final product.

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I'll look into getting a better one for my next batch, but this'll have to do for tomorrow! I am just using one of the recipes my LHBS has - I think the "mash" is more of a "steep" - getting flavour and colour out of them, but not much fermentable sugar. I'm trying to gather equipment for a move to all grain so I will move "good thermometer" to the top of my list:rockin:

In the meantime if you have any ideas for other temperatures I could compare it to? I could heat some water up to ~38*C and compare the reading from my body temp thermometer to my meat thermometer. 3 points of reference

All the meat thermometers I have like that say not to use them in water, not sure why but that might be a problem. I bought what seems like a nice thermometer online for $20, both the housing and the probe are fully submersible and the probe measures from -40 to 300 F. Should get here tomorrow or the day after, then I'll test it out.

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What kind is it swordsman - could I get a link? I was reading in another thread about people's recommendations, and they were all in the $50-100 range, which seemed a little steep. This 5 dollar one says it is "good for sauces and liquid and hot milk froth" so it should work for now

The most accurate thermometer I own is one similar to this:
http://www.amazon.com/Taylor-Digital-Instant-Read-Pocket-Thermometer/dp/B00004XSC3

The one I have is a Taylor, but a slightly different model. Mine has a small plastic screw on the face of it that I can twist for calibration. That one is more accurate than any of the long probe digitals I have (one for the brewery and one for the kitchen), as well as the two analog probe ones, and my floating one. The Taylor digital I use reads 32.2*F in crushed ice water and 211.9*F in boiling water.

edit: Found a link. This is the exact one I use, yellow and everything:
http://www.amazon.com/Taylor-9842-C...Thermometer/dp/B00009WE45/ref=pd_bxgy_k_img_b
http://www.amazon.com/exec/obidos/r...Thermometer/dp/B00009WE45/ref=pd_bxgy_k_img_b