Thermometers. huge variations. FYI

[Don Runk]

Don't know exactly what you guys do but i've been struggling with reading accurate temps across the board.

my Infrared is supposed to be unreliable on liquid surfaces.
I have a k type multimeter type thermometer that reads whatever it feels like on the day.
kitchen thermo's readings vary.
i calibrated my boil/mash kettle dial thermo and i have been trusting it as the best i own.
my pid's are swinging wildly (found out you cant extend thermocouples!oops!)

i have about 10 thermometers and basically none of them line up/ can be trusted. i'm talking 3-5c variations.

so i went to wiltronics and bought 5 glass scientific thermometers. For science! surely they'll be right? right?

wrong..

i got
2x ECONOMY GLASS MERCURY THERMOMETER -10 to 110 but they sent the more expensive YELLOW BACKED MERCURY THERMOMETER -10 to 110
2x BLUE SPIRIT WHITE BACK THERMOMETER -10 to 110
1x YELLOW BACKED SPIRIT THERMOMETER -10 to 110


The end result is the mercury ones were wildly wrong at each end of the scale like -10c to 107c. strait in the bin.

Out of the spirit ones they all read a pretty constant but not all the exact same -1c in ice slurry but 101-101.5c in boiling water. they also vary by a degree at 65c


so i now have 15 thermometers that don't line up. but if anyone is looking i'd suggest the blue spirit white back at $3.50 you cant really go wrong and is way more accurate than their most expensive model and the easiest to read.
Link - http://www.wiltronics.com.au/catalogue/180803/science/thermometers

am i being too anal with my thermometers? (might even try that at this point)

looks like i'm giving up and going with the best of all evils. but F%$$# me how hard can it be to measure temp accurately?

any tips?

 

[barls]

buy one decent one ive got a glass one that i got calibrated and then set everything off that.
my digital one is within .5 degrees of the glass one so im happy.

 

[Don Runk]

that's my problem i thought i bought 5 decent ones to find they are all varying to some degree.

how do you get a glass themo calibrated? do they reprint the graduations or something? where did you get it done?

 

[barls]

i bought it that way.
saying that my digital was nearly 100 bucks and if i was to do it again id buy a therma pen.
Thermapen thermometers - GrillGr8
ive got one of their lower end ones currently.

 

[barls]

also infra red is no good as its only doing the surface temp at the time. then you have to factor in the loss due to reflection and other crap. the only time its any good is in fire fighting and then its still only as good as the user.
the other point is how are you comparing them? ive always like this method
Calibrating a Thermometer - YouTube

 

[Don Runk]

Thanks Barls,
I only ever use my infrared to see if i'm in the ballpark and never trust it (but i have trust issues with all my thermo's it seems)

thanks for the vid, thats exactly how i calibrated my keggle dial thermo and how i tested the scientific thermos to find they were off.

the whole thing is such a trap to be honest. i wonder how many brewers are out there that paid good dollar and assumed they got a quality thermo and are trusting it when it could be 3 or more degrees out in the mash range. Heaps i assume.

to top it off i read somewhere that even if your thermo reads 0 in ice and 100 in boiling doesn't guarantee it is accurate at 65... f me!
there is some method of melting mothballs or something to test at closer to mash temps. - someone more anal than me perhaps?

 

[manticle]

I have 2 glass stick thermometers that are within less than 0.5 degree C of each other in iced water, cold tap water, boiling water, inside the temp controlled fridge and in the mash. They also read very close to the STC-1000 ambient reading when in the fridge (less than 1 degree difference).

Add to that that I get similar results to expected when mashing/fermenting and I'm OK.

Having as many as you do of so many different types will be confusing as they are accurate at different ranges. I can understand if all your alcohol ones differ wildly from each other that you would be upset and if they are all from the same manufacturer, you have recourse for return and refund.

 

[Don Runk]

Thanks mantacle, I'm not upset or after a refund or anything just frustrated I can't get it 100% right.

I guess the moral of the story is just get as close as you can. I'll use the two spirit ones that are closest and be happy with that.

Was posting to let people know as much as to get opinions.

Might look into a thermopen. Will be gutted if that's off too! ;-)

 

[manticle]

Thing is with so many - you won't know what's off and what isn't.

Systems are never 100% accurate so you need to find the point in the range where you get the results you want and measure that. Then aim for consistency in understanding how to use your system.

 

[barls]

this is the one ive been using from their range.
http://www.thermoworks.com/products/low_cost/rt600b.html
bought it yonks ago with a couple of other mates.
even the thermapen is adjustable up to a couple of degrees when bought but comes with NIST-Traceable calibration certificate so you shouldnt have to cal it.

 

[squirt in the turns]

Manticle's point about getting expected results is key. We have to accept that our thermometers are going to be flaky. For the mash, I just calibrated my PID based on boiling water and ice, and have tweaked it a little since to get my beers attenuating where I want them for the mash schedules I use. I think if I were to retest my PID/PT100 set up in ice or at boiling again, it'd read a couple of degrees under what's expected, but for temps in the range of 60 to 75, it's doing more or less what i want.

Of course, attenuation will be influenced by yeast choice (and health, and pitching rates, and probably to an extent by the fermentation temperature as maintained by whatever thermometer controls your heating/cooling apparatus). As much as you can try to introduce repeatability and control every aspect of the brewing process, there is a lot of room for uncertainty in home brewing. I just see it as part of the fun.

 

[Don Runk]

Thanks alot guys, all taken on board.

I'll use the best I have, learn how my system behaves and take it from there.

I am only 15 or so brews into AG so my obsession began trying to get repeatability and recipes nailed. Which I'm sure I will with time.

It's still amazing the variation you can get in thermo's though.

Obsession over. I can stop buying thermometers now and buy more hops!

 

[QldKev]

As above, I have one alco filled thermometer which I use as my guideline. All my PIDs & STCs are calibrated by it. Then I adjust my brew schedule to get my desired results.