Digital Thermometer Accuracy

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evanvine

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Having read the previous threads on digital thermometers I am still not finding the info I want.
I’ve been looking for a Digital Thermometer to use as a reference for calibrating my PIDs etc.
I have used the melting ice method, but seem to get different results each time.
The more I trawl the web sites, the more confused I get!
My thoughts are 0.1C resolution and +/- 0.1C accuracy.
Prepared to pay £ 40 – 60, does such a beast exist?
I have the “Hygiplas” at the moment and it is nowhere near accurate enough!
At 65C it has a 2C error, this would be acceptable if it was linear.
 
I don't use a digital thermometer as a reference, but I do have a 'certified' mercury thermometer which is my reference. From what I have seen from cheap and expensive digital thermometers they all tend to 'drift'. I 'map' my digital thermometers and 'thermocouples' to my mercury one once a year.

Basically heat water to boiling then record temp displayed on all thermometers at boiling. . . . switch heat off and as it falls record the temp at 5C intervals (on the mercury). use ice water to get below about 20C and to get to an indicated 0C. This then gives you a temperature map for each digital device. that you can use for compensation purposes.
 
Thank you both for your replies.
I have seen then at £750 and thought I was on a hiding to nothing.
Is that the sort of price you were talking JB?
At the moment I have an alcohol thermometer, but don't know its accuracy, will check it in ice water.
Also going to look at Mercury ones.
I like your calibration idea Tony.
 
the thermometer i use comes from a volt meter/ohms electrical tester, got it for nothing brand new from my brother ,apparently its worth a few hundred quid it seem accurate when i compare it to the 2 mercury ones i have this might be a cheaper alternative, and you also get an eletrical testing device to boot. :cheers:
 
Laurin said:
You best bet might be to use a body thermometer they have not a huge range but usually quite a high accuracy. I found one on this site which is supposed to have an accuracy of +/- 0.05C.

http://www.dealextreme.com/p/0-8-lcd-so ... 225-117431

Dealextreme ship directly from China so it might take a couple of weeks or so.


The range they quote is only 34-42c or have I misunderstood something? If so it's not even going to get to mashing temps :hmm:
 
The range is not enough, but I thought you could use it to check and maybe calibrate other thermometers, because the accuracy is quite good.
 
Laurin said:
The range is not enough, but I thought you could use it to check and maybe calibrate other thermometers, because the accuracy is quite good.
Certainly cheaper than the £65 calibration certificate they talk of here http://www.thermometersdirect.co.uk/aca ... meter.html.
I have the cheap version of this and really like the probe on a long lead, a lot easier to read too as you can keep the display away from any steam. Problem is it isn't accurate and wobbles about too much before reading "true". I would also caution about leaving them in the HLT to measure there, my probe softened and lead to it completely breaking down, all this on my first brew day, much else besides.
 
Well you can measure at 34C at 43C so you have two reference points, fair enough they are quite close. The accuracy is really good though and at £12.05 quite a bit cheaper than a few hundred quid.
 
orlando said:
Certainly cheaper than the £65 calibration certificate they talk of here http://www.thermometersdirect.co.uk/aca ... meter.html.
I have the cheap version of this and really like the probe on a long lead, a lot easier to read too as you can keep the display away from any steam. Problem is it isn't accurate and wobbles about too much before reading "true". I would also caution about leaving them in the HLT to measure there, my probe softened and lead to it completely breaking down, all this on my first brew day, much else besides.

That's a UKAS calibration certificate. We don't need anything like that. The in-house one is fine.

I use this one, and paid for the calibration and will get it rechecked every year.

Mine doesn't really "wobble" about though.

Jim - Accurate, Repeatable, Cheap. Pick any two.
 
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