Which master's specialisation suits a BTech graduate in Electronics and Instrumentation with 4 years of work experience?

An Electronics and Instrumentation background already gives you measurement, sensor, electronics and control foundations, so the strongest master's builds on whichever half of that foundation your four years of work actually deepened, rather than repeating a generic electronics curriculum. This question does not name a study destination, so the specialisation below applies broadly before you narrow to a specific country's programmes.

Why Embedded Systems Or Control Systems, Not A Generic MS Electronics

• Embedded Systems / Embedded AI: firmware, microcontrollers, IoT and RTOS work extends naturally into embedded engineer and firmware architect roles.
• Control Systems / Automation / Robotics: PLC, DCS, SCADA and industrial automation experience extends naturally into control engineer and automation engineer roles.
• Avoid the default: a generic MS Electronics Engineering that mostly repeats your bachelor's gives you less of a specific technical identity than either of the two paths above.

My Advice

Do not automatically choose a generic MS Electronics Engineering just because your bachelor's is titled Electronics and Instrumentation, with four years of experience your master's should give you a specific technical identity rather than repeating your undergraduate education. The country you eventually choose changes this ranking considerably, immigration and job-market conditions differ substantially across the USA, Germany, Canada, Australia and the UK, so narrow your destination before finalising the university shortlist, and share your exact job role and technologies used with your counsellor in the meantime.