Instrumentation is the science of measuring and controlling variables. Variables are anything that can affect or change other things. Instrumentation can be used to make processes faster or more efficient, meaning they use less effort, energy or money to produce the same results.
The word instrumentation may also mean the machines made to measure and control things.
The science of instrumentation involves figuring out the best way to measure or control something, building the machine or tools, and checking if the results are good and true. It may also include setting up and using the machine or tools.