Instrumentation engineering is a branch of engineering that specializes in measuring instrumental values and operating scientific instruments. That includes, instruments in the field of science, designing, development, research, and also medical. It could be a field that works in support with mechanical engineering on field. Instrumentation engineers play important role in improving the productivity, reliability, safety, optimization and stability of instruments in the work station.

Coming to the job opportunities,

You may work in designing and production

measuring values in essential fields like astronomy, nuclear plants, and other scientific organizations like ISRO and DRDO too.

Aircraft sensor building and designing and monitoring, medical cardiograms and instruments related to operations and critical equipment.

So simply, you can find employment in manufacturing firms, defense contractors, biomedical companies, government, or work for private engineering firms.

For further studies, you can do masters in instrumentation engineering, communication systems, database systems, digital electronics, micro controllers, applied physics and robotics and various other fields.

You have a lot of masters option in countries like Germany, japan, Canada, And India too.

I hope i answered your question.

feel free to ask any doubt in comments.

Good Luck