Hi friends,
a new problem faced me while i was reading about calibration of glass thermometers,i found in NIST publication 819 that he calculated the adjusted scale correction but i didn't understand how he calculated it:bonk:
please i want to understand it and i want to diffrentiate between "the adjusted scale correction" and "the correction" (that we calculate normally)..


best regards,
Mohammed Gouda..:bigwave:

Hi friends,
a new problem faced me while i was reading about calibration of glass thermometers,i found in NIST publication 819 that he calculated the adjusted scale correction but i didn't understand how he calculated it:bonk:
please i want to understand it and i want to diffrentiate between "the adjusted scale correction" and "the correction" (that we calculate normally)..


best regards,
Mohammed Gouda..:bigwave:"Be like mercury,useful to friends...poisonous to enemies"

Liquid thermometers are relatively cheap and depending on how critical the reading is and the margin of error allowed, they are normally replaced if found to be out.

With regards to error in the scale, the simple academic approach is to determine how much it is out (at both boiling/ice point) and then distribute the error out linearly. I am not sure how the lab guys or metrologist do it.

:bigwave:Liquid thermometers are relatively cheap and depending on how critical the reading is and the margin of error allowed, they are normally replaced if found to be out.

With regards to error in the scale, the simple academic approach is to determine how much it is out (at both boiling/ice point) and then distribute the error out linearly. I am not sure how the lab guys or metrologist do it.
Thanks mr. Harry for your reply..but i am still confused from these points (ice point & boiling point) that:
i-when i recive the thermometer from the customer,i record the ice point readings.
ii-after calibrating the glass thermometer by comparison with two reference thermometers,i repeat the ice point check.

the question is :the change in readings of ice point (if it was found after calibration)indicates the change in bulb volume after calibration ...so all readings will be shifted upwards or downwards after doing calibration which also indicates the change in corrections afterwards...does it mean that calibration will be repeated??

I am not sure if I understand you but I'll try.

1. Lower quality thermometers will produce errors after prolong usage due to expansion of the bulb (size increase) which indirectly gives an error in the reading/scale.
2. Amount of error will depend on range of temperatures used and period (time) of usage. Thus thermometers that were used for longer periods or higher temperatures tend to have more bulb expansion.
3. After a period of time (normally you determine it), you need to recheck or recalibrate.
4. One way is to check the reading at ice point. If the zero reading now reads minus one degree (as simple illustration), it means every reading along the scale is out by minus one degree. If you now use this same thermometer to check boiling point, the correct boiling point is now (100-1) degree.

that's it,mr. Harry...
thanks alot:applause: