How do you design instrumentation to meet EMC immunity requirements and troubleshoot immunity failures?

EMC immunity design and troubleshooting: design for immunity margin beyond minimum requirements (IEC 61326 for industrial, higher for power stations), implement filtering at all entry points (power, signal I/O, communication), shield sensitive analog circuits (grounded enclosure, filtered connectors), and use robust circuit topologies (balanced inputs, high CMRR, bandwidth limiting). Testing: RF immunity (EN 61000-4-3), ESD (4-2), EFT (4-4), surge (4-5), and conducted RF (4-6). Troubleshooting failures: identify susceptible frequency/port combination, probe internal nodes during exposure, add filtering progressively to identify entry path, verify ground continuity at RF frequencies, and check cable shield terminations. Document susceptibility analysis and corrective actions for design database.