[a10t2]

My digital thermomter is reading 209* sitting in boiling water. I'm in the midwest, so it's not an issue of sealevel.

Where exactly? I was at 900' in West Lafayette, which would put you within 1°F.

[Pricelessbrewing]

Another happy rt600c owner.

For what it's worth I bought a refurbished one a couple months back (about the same price as the $15+shipping going on now), used it for a brew or two before testing it. Tested it, found it read ~2F high at freezing, ~3F high in mash, and 4F low at boil. Emailed them, they sent a brand new replacement and a certification of calibration along with an email from a QA employee. Very happy with their customer service.

Only thing is that it's not able to be re-calibrated. I suppose down the line it may become an issue eventually, in which case I have no doubt they will send a replacement of a similar product due to their awesome warranty. If not, I have no qualms buying another one.

If the ability to calibrate is something you're interested in, the 301 is probably the model you'd want.

[PORTERHAUS]

My digital thermomter is reading 209* sitting in boiling water. I'm in the midwest, so it's not an issue of sealevel.

Where exactly? I was at 900' in West Lafayette, which would put you within 1°F.

Im at about 630 ft. I never knew that little made a difference. I figured It was 212* for me when after looking at a chart its more like 211*. I calibrated the digital with the ice water solution where I got my lab thermometer to finally read as close to 32 as I think I will get it. One thing I havent done is see what my lab thermometer reads in boiling water then compare to the digital. I use the digital a lot in the masb becaise its quick. But it has to accurate so ill do that test next.

[Whiskers]

Don't assume that a glass 'lab' thermometer is any better than a degree or two off at 100degC.  I'd expect a thermapen to be better than that out of the box.  I don't know what sensor they use, but I doubt it's an RTD.  I have a collection of various RTD's and while some of them read (via Watlow instrumentation) 0.3-0.4degF off from one another, this difference hasn't changed over many years of use/sitting around. 

I have a thermapen too and it's a nice little bit of kit.  It was ~0.2degF off in both boiling and ice slurry when I got it.  Never have checked for drift. 

[mabrungard]

While boiling point calibration is better than nothing, remember that we brewers are most interested in the 120F to 180F range. That's where we want to assure accuracy. That is when a certified lab standard is valuable.

I have a NIST certified mercury thermometer that only comes out of its case when its time to check and calibrate my working thermometers. I share it with my club at calibration events too. Fill an insulated water keg with 150F +/- water and put everyone's thermometer in the vessel.

[reverseapachemaster]

I'm another happy rt6000c user. I'm among the crowd that couldn't justify spending four times as much on a thermapen. The thermapen claims accuracy +/- 0.7F and a three second reading while the rt6000c claims accuracy +/- 0.9F and a six second reading. I couldn't justify an extra $60 over three seconds and 0.2F.

[Stevie]

I'm another happy rt6000c user. I'm among the crowd that couldn't justify spending four times as much on a thermapen. The thermapen claims accuracy +/- 0.7F and a three second reading while the rt6000c claims accuracy +/- 0.9F and a six second reading. I couldn't justify an extra $60 over three seconds and 0.2F.

Most of the people I know with thermapens are also kitchen gadget nerds. rt600c 4EVA

[HoosierBrew]

I'm another happy rt6000c user. I'm among the crowd that couldn't justify spending four times as much on a thermapen. The thermapen claims accuracy +/- 0.7F and a three second reading while the rt6000c claims accuracy +/- 0.9F and a six second reading. I couldn't justify an extra $60 over three seconds and 0.2F.

+1.  The difference is pretty negligible in the big scheme of things.

[PORTERHAUS]

While boiling point calibration is better than nothing, remember that we brewers are most interested in the 120F to 180F range. That's where we want to assure accuracy. That is when a certified lab standard is valuable.

I have a NIST certified mercury thermometer that only comes out of its case when its time to check and calibrate my working thermometers. I share it with my club at calibration events too. Fill an insulated water keg with 150F +/- water and put everyone's thermometer in the vessel.

Thats exactly what I was going to ask about next was mash temp range calibration. I have heard to do it that way skimming over threads like this. When I bought my lab thermometer from McMaster a couple yrs ago it wasnt cheap. Something like $35 sounds familiar...pretty sure it also came with a certificate. Ill note temps in the 150 range and see how that goes.

[pfabsits]

All electronic devices will drift overtime and with temperature. It is inevitable. Thermometers less than $20 or ones from the grocery store are not very accurate. They usually are around 2-3 oF in accuracy. The Checktemp from Hanna is on the expensive side but has the Cal-Check function and an accuracy +/- 0.5 oF (-58 to 199.9 oF range). It is +/- 1 oF outside the range.

http://shop.hannainst.com/hi98501-checktemp-digital-thermometer.html

Cal-Check is an internal diagnostic function of the electronics. When switched on it should display "0". Any drift will show as a deviation from "0"

Thermometers fall into three categories:
Thermistors
Thermocouples (K-type being the most common)
PT100

Thermistor is a semi-conductor device that resistivity changes with temeprature
Thermocouples consist of probe with two wires of different metals twisted together (hot junction) that have a potential difference based on temperature
pt100 is like a thermistor in which there is an increase in resistance that is measured but it is a resistance of a metal conductor (RTD) made of platinum with temperature and not a semi-conductor (thermistor - NTC, PTC).

Thermistors have limited ranges of around -50 to 302 oF and offer high accuracy
Thermocouples have very wide range based on type (K,J,T, etc). For example a K-type wire probe spec can be up to 2000 oF but not as accurate as a thermistor.
pt100 have a wide range, up to 1650 oF and high accuracy.

Thermocouples have the fastest response. The fast response time of the thermocouple is one of the reasons it is the technology chosen in restaurants. we offer probes as fast as 4 second response time to reach 90% of the value. Thermistors probes can be fast as well. We have some in the 6 second response time to reach 90% of the value.

The pocket thermistor thermometers are the most common due to price. Portable themometers will start in the +$100 dollar range. With thermocouples there are two types of calibrations. The internal meter calibration is for the "hot junction" which is where the probe connects to the meter. This has to be done with temperature controlled baths at multiple points. There are also meters with probe calibration feature in which the "cold junction" is calibrated by placing the probe in an ice bath. An ice bath should be prepared with crushed ice made from DI water. Any salts will cause freezing point depression in which the water will freeze below 32 oF. Some portable thermistor thermometers also offer a ice bath calibration feature.

[Jeffinn]

While I will agree that my Thermpen was a money burning a hole in my pocket purchase, I love the thing.  I have found all kinds of uses for it.  I do not know if the other Thermoworks products do, but the Thermopens come with a certificate of calibration.

+1 to this. The Thermapen is a great thermometer!

[RPIScotty]

I was checking the junk drawer today and forgot I bought this $10 Taylor digital thermometer this year to check the bird. I pulled it out and calibrated it using the trim pot with an ice bath and its solid!

It lags a bit on temp but it's accurate.

[Whiskers]

I've been through a few of those taylor-type units, including taylor brand.  I might not have treated them as well as I could have though.  Perhaps thermometers are bit like sunglasses?