Dear Lab Guy,
I’m trying to buy a thermometer and I see reference to partial immersion and total immersion. I have no idea what that means! For total immersion do you need to completely immerse the thermometer? How far do you have to immerse a partial immersion thermometer?
That’s a great question Dominick!
Partial and total immersion is a subject that confuses many, even those that work with liquid-in-glass thermometers every day.
A partial immersion thermometer should be submerged to the immersion line visible on the back of the thermometer to achieve proper accuracy. They are useful when total immersion thermometers can’t be used, such as in a shallow bath.
A total immersion thermometer must be submerged to within 1 cm of the thermometer column's liquid level for an accurate reading, and adjusted as this level changes while measuring the temperature. Total immersion thermometers have better precision than partial immersion thermometers because it eliminates air temperature variables, however, don't confuse that with accuracy. Both partial and total immersion thermometers should be accurate as reported ‘as long as they are used properly’.
Check out this FAQ that provides more information about partial and total immersion, as well as calibration reports, PFA coating, proper storage and more.