Hi friends,
i would like to ask some questions:

1-what is the optimum liquid bath depth which is needed to calibrate glass thermometers ??

2-also,can i calibrate the total immersion thermometer as a partial immersion and add the emergent liquid column (elc) correction to compensate the change between the set point and the measured one?
(if the depth of the bath isn't sufficient to complete at deeper immersion)

thanks alot...

Mohammed Gouda..:bigwave:

To my knowledge,

1. Depends on the type of thermometer - total immersion, partial immersion or complete immersion type. There is no optimum - you need to calibrate it the way it is intended to be used.

2. You cannot calibrate it this way but for practical purpose, you may read it this way and compensate the readings using some calculation methods recommended in NIST documents. This is not applicable to the complete immersion type which must only be calibrated and read in the immersed condition.

KISS :2cents:

If it is practical, switch to a digital thermometer. Partial, full immersion does not come into play.

From my experience, the partial immersion glass thermometers I have used have always had a mark indicating the immersion depth to be applied.

ok,Mr.Harry

i know that it isn't able to be applied for complete immersion thermometers,but :

1- i noticed that not all the liquid baths able to make calibration for tall total immersion thermometers,how we can use it??

2-the equation which is found in NIST is for compensating the emergent liquid column measurement...so we can take the readings and correct it,doesn't it?

Theoretically, the bulb of the completely immersed type is subjected to a different pressure in the immersion stage compared to the partially immersed type so it is not recommended to be calibrated as you suggest. If you do not have the right equipment, I don't see other ways unless you want to play around with the uncertainty figure. For this, I think you need relevant knowledge and data to back you up.

I am not too sure whether you are pursuing this for knowledge or practical purpose. In practice, the cost of doing these things (equipment, people and hassle) is just too high and for critical operations, people nowadays choose to get better quality ones (single calibration is enough) and replace them when the need arise.

Theoretically, the bulb of the completely immersed type is subjected to a different pressure in the immersion stage compared to the partially immersed type so it is not recommended to be calibrated as you suggest. If you do not have the right equipment, I don't see other ways unless you want to play around with the uncertainty figure. For this, I think you need relevant knowledge and data to back you up.

I am not too sure whether you are pursuing this for knowledge or practical purpose. In practice, the cost of doing these things (equipment, people and hassle) is just too high and for critical operations, people nowadays choose to get better quality ones (single calibration is enough) and replace them when the need arise.
yes,Mr. Harry...but i am talking about "totally immersed therm." not "completely immersed therm."

the correcting equation for "total" immersed thermometer,not for "completely" immersed one...
i know the diffrence between both...but i want to apply this equation during calibration in case of the immersion depth isn't sufficient to insert the totally immered themometer till it reaches high temp.:confused:

i am really confued ...:(

but really,thanks for your concern:read:

thanks alot..
Mohammed Gouda...:bigwave:

Mohammed, I'm sorry I cannot help on this one. The thermometers that we do in-house (partial and total), we immerse as deep as possible to get sufficiently good readings.

yes,Brad...i know..

but how can you overcome the extra needed depth for immersing a total immersion thermometer ?? will you buy deeper liquid bath??
i think this isn't easy to do..

but i read SP250-23 twice and found that we can compensate the readings of the total immersion when it isn't been immersed as usual (shorter and emergent liquid column is found)...and the equatin used can make the reading approx. uncertainity 10% (with confidence level 95%)..

so by this correction we can calibrate this thermometer by comarison method to standard thermometer....(also see "traceable temperature" chapter 7...the author told that he could use at thermocouple adjacent to the emergent liquid column (elc)and make the correction on the readings taken..:frust:...i'm still confused

best regards..
Mohammed Gouda.. :bigwave:

hello, Mohammed!
And yes, we buy deeper baths; Hence the reason we get rid of glass thermometers. In the end, you need to see how much variance you accumulate due to immersion factors.

i got you ...mr. Brad
But all i tried to understand the extent that we can apply this equation...i work in a calibration lab and some customers have long thermometers need to be calibrated by total immersion...so i read a catalogue for "ALLA-FRANCE" and they referred to that problem..

thanks ....

Mohammed Gouda....