How to "Anneal" a Glass Thermometer

[Mohammed Gouda]

hi friends,

i would like to ask about "annealing" the glass thermometer before calibrating it...


Best regards...
Mohammed Gouda...

 

[Ajit Basrur]

Re: how to "anneal" a glass thermometer ?

Hi Mohammed,

Being a weekend, the responses are bit slow......... so wait until 1 - 2 days to get good answers to your question.

 

[Mohammed Gouda]

Re: How to "anneal" a glass thermometer ?

is the annealing process as that we do with SPRT??

 

[Marc]

I know this is an old one, but it is unique. Can anyone help with "This Old Thread"? My Thanks in advance!

 

[apestate]

Looks like SPRT means Standard Platinum Resistance Thermometer

From wikipedia: Resistance thermometers, also called resistance temperature detectors or resistive thermal devices (RTDs), are temperature sensors that exploit the predictable change in electrical resistance of some materials with changing temperature. As they are almost invariably made of platinum, they are often called platinum resistance thermometers (PRTs). They are slowly replacing the use of thermocouples in many industrial applications below 600 °C, due to higher accuracy and repeatability.

It appears from GIDEP data that platinum resistance thermometers are annealed during calibration.

It does NOT appear that a standard glass thermometer is annealed, however. If I read the question accurately, I'd say the answer is "don't." :>

Anyone else ever heard of annealing a thermometer?https://en.wikipedia.org/wiki/Resistance_thermometer#cite_note-0

 

[harry]

Annealing_(glass) is a process of slowly cooling glass to relieve internal stresses after it was formed. Almost everything made of glass would had undergone this process.

All thermometers would had undergone such a process during the initial stages of manufacturing. Given it's odd shape and different thickness along the whole length, I think some proprietary process must had been used.

 

[George Weiss]

SPRTs or PRTs in general, which are temperature sensitive resistive devices are/can be taken to at/near/above (500deg. C.) maximum temperature for a set period of time, say 1 hour, and then cooled slowly.
A liquid, (mercury or other), filled glass thermometer will have varying temperature full scales, and would not be annealed. The accuracy/specification of the liquid filled glass thermometer also limits the need for this annealing.
SPRT/PRT +/-0.01deg.C
Glass thermometer +/- 1.0deg.C or +/-1% of range
Burns Engineering paper on PRT error sources @
https://www.burnsengineering.com/document/pdf/a080306.pdf

 

[ScottBP]

We occasionally get mercury-in-glass thermometers where a bubble has developed in the middle of the mercury column, pushing the top of the column up a bit to make it read higher than the temperature actually is. To remedy this, we cool off the thermometer just enough to shrink the mercury all the way down into the reservoir at the bottom, thus getting rid of the bubble. (Call it reverse-annealing?) This is easily done with a mixture of dry ice and 100% ethyl alcohol (denatured of course ).

 

[George Weiss]

yes a good point ! ! ! !
I am sure the original poster has long moved on, but the comment was worthy !
I wonder how many still use the mercury filled glass thermometers.
I was an observer in a hazmat clean-up after one broke as it hit the floor. A measureable amount of mercury escaped, and there was people in hazmat suits everywhere. OMG.
fortunately the spill was small. Over a certain amount the building would have been cleared.

 

[Mike Boothe]

Check out NIST SP1088 Maintenance and Validation of Liquid-in-Glass Thermometers (January 01, 2009).
https://www.nist.gov/manuscript-publication-search.cfm?pub_id=900914