Question

What are the 2 important things that he does upon using thermometer​

Answer 1

Explanation:

A thermometer has two important elements:

(1) a temperature sensor (e.g. the bulb of a mercury-in-glass thermometer or the pyrometric sensor in an infrared thermometer) in which some change occurs with a change in temperature; and

(2) some means of converting this change into a numerical value (e.g. the visible scale