Thermometer calibration at hot and cold temps
Hello!
My company has historically verified thermometer accuracy against ice bath and hot water bath. I've discovered that the thermometer manufacturer recommends ice bath only for their digital thermometers. Can anyone supply a study or other documentation verifying that ice water bath only is sufficient? For reference, we temp both hot and cold items during production.
Thank you!
Hello!
My company has historically verified thermometer accuracy against ice bath and hot water bath. I've discovered that the thermometer manufacturer recommends ice bath only for their digital thermometers. Can anyone supply a study or other documentation verifying that ice water bath only is sufficient? For reference, we temp both hot and cold items during production.
Thank you!
If your acceptable range is a wide then you would probably be better served by a two or three point calibration that includes a value slightly above and below your acceptable values. Freezing and boiling are easy to replicate.
If your pass/fail is a single value or very narrow temperature such as frozen/not-frozen then a single point calibration for the instruments may be reasonable.
Curious - where does it say that you have to use both? If the thermometer is the correct temperature in the ice water bath, then why wouldn't it be in a hot water bath. Most regulations say you must calibrate a thermometer using a proper calibration method. I work in a USDA/FDA facility - we calibrate our hand held thermometers using a calibration machine with cold temp only. We do make some cooked items that are temped by our hand held thermometers. Neither the USDA, FDA or SQF has questioned our calibration methods.
Curious - where does it say that you have to use both? ...
Have to? Nowhere probably. Most regulation isn't that specific.
That doesn't mean it isn't best practice or advisable. I've seen plenty of thermometers that theoretically have a range over a hundred degrees and work perfectly fine within part of it, but are miserably inaccurate with higher and/or lower temps. Not only adjustable bimetallic coils, but sealed glass units too.
Curious - where does it say that you have to use both? If the thermometer is the correct temperature in the ice water bath, then why wouldn't it be in a hot water bath. Most regulations say you must calibrate a thermometer using a proper calibration method. I work in a USDA/FDA facility - we calibrate our hand held thermometers using a calibration machine with cold temp only. We do make some cooked items that are temped by our hand held thermometers. Neither the USDA, FDA or SQF has questioned our calibration methods.
We've been using the Thermometer Calibration Guide by Kansas state which recommends both. But I'm aligned with your thinking. I'm looking for similar written guidance to match the thermometer manufacturer's specs.
A difficulty with only ice point being used is that thermocouple reading with temperature is usually non-linear so typically becomes relatively inaccurate at 100degC. I guess the digital manufacturers like the ice point because it's easy to set up.
Professional calibration Services claim to use "high Grade" ice + controlled environments. Or black boxes.
IMEX some digital thermometers/probes don't like boiling water so I use the steam generated.
I would agree with Charles that the housing of the thermometer may not stand up to the steam/boiling water and that is why the ice bath method is recommended
For a second (or third) point of calibration the black body target works well for digital units -- they're hard to beat if you need to verify hitting a high cook temp for a lethality CCP with a critical limit above boiling. It's hard to say you're confident in the thermometers' ability to measure 150F or 250F accurately if you only verify calibration at 32F.
https://www.thermowo...m/blackbody-ir/
Without financial support for a selectable high temp unit, a basic ambient cup or block style is an affordable alternative. The confidence level at high temps won't be as good, but it's still better than a single point. Boiling water will be better for most probes, but for IR this is safer and easier to execute.
https://www.thermowo...comparator-cup/
For a second (or third) point of calibration the black body target works well for digital units -- they're hard to beat if you need to verify hitting a high cook temp for a lethality CCP with a critical limit above boiling. It's hard to say you're confident in the thermometers' ability to measure 150F or 250F accurately if you only verify calibration at 32F.
https://www.thermowo...m/blackbody-ir/
Without financial support for a selectable high temp unit, a basic ambient cup or block style is an affordable alternative. The confidence level at high temps won't be as good, but it's still better than a single point. Boiling water will be better for most probes, but for IR this is safer and easier to execute.
Hi GM,
Links maybe only for IR units ? 1000 US $ !! I believe typical IR accuracy is generally (and acceptably) regarded as below officially calibrated thermocouples ?
I think oil baths are the most common Official technique for (non-crazy) temperatures > 100degC ? Although IMEX they are not particularly user-friendly (fume cupboard).
Some Professional Services use "Smart" Black Box methods. Convenient but IRC also not cheap for infrequent usage.
Perhaps surprisingly I believe some cookers/canners still rely on Hg instruments as a Primary reference.
IMO, it's generally preferable to utilise a Quality, Master, externally calibrated, thermocouple and then self-generate sub-Masters as required. Although some operations may demand dedicated calibrated instruments, eg canning.
Dataloggers are another popular solution of course. At a Price.
IR units are certainly convenient for passive sampling applications though.