Hi Aspirant,

Instrumentation engineers are those who does works like measuring,researching and installing,developing,testing,maintaining and also designing of the instruments and the machines used in the industries.Instrumentation engineer  also formulate ways for efficient working of the machines and also deals with several problems related to machines.However electronics engineers deals with electronic parts and working of the small electronic devices along with completion of the functions of various semiconductor devices like mosfet,jfet etc.

hope it helps!!