Electromagnetic Interference EMI Investigations and Remediation Solutions

We identify the root cause of your equipment’s malfunction and conduct non-invasive tests and troubleshooting techniques to provide the most appropriate solutions.

Industrial, Scientific, Medical

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An EMI investigation (Electromagnetic Interference investigation) is a systematic technical process used to identify, characterize, and resolve unwanted electromagnetic emissions or coupling disrupting electronic systems' performance, compliance, or safety.

Purpose of an EMI Investigation

  • Diagnose the source of unexpected interference in a system or environment.

  • Trace the coupling path (conducted or radiated) from emitter to victim.

  • Quantify the EMI in frequency, amplitude, and mode (common or differential).

  • Determine root cause (e.g., design flaw, grounding issue, shielding failure, poor filtering).

  • Implement mitigation strategies to restore reliable and compliant operation.

When an EMI Investigation Is Needed

  • Electronic equipment experiences resets, lockups, or malfunctions.

  • A product fails EMC compliance testing (FCC, CE, CISPR, etc.).

  • Communication systems show signal degradation or data corruption.

  • EMI affects sensitive medical or scientific instrumentation.

  • Facilities report audible noise, flickering lights, or RF interference.

  • Ground loops or unexpected current paths cause equipment failure.

  • EMI causes harmonic distortion, transient spikes, or power quality issues.

Tools Used in an EMI Investigation

  • EMI Receiver or Spectrum Analyzer (for frequency-domain analysis).

  • Near-Field Probes (E-field, H-field, current probes for localized scanning).

  • Oscilloscope with Differential Probes (for waveform analysis and transient capture).

  • Line Impedance Stabilization Networks (LISNs) (for conducted emissions testing).

  • Clamp Meters or Current Probes (for ground loop or leakage current detection).

  • RF Antennas and Directional Couplers (for radiated EMI tracking)

  • Power Quality Analyzers (for harmonics and switching noise).

  • Conducted and Radiated Emissions Software (for data logging and comparison to EMC limits).

Typical Steps in an EMI Investigation

  1. Define the Symptoms

    • Describe the failure modes, operational environment, and system behavior

    • Identify when and where the issue occurs (e.g., startup, under load, intermittently).

  2. Preliminary Inspection

    • Inspect PCB layout, cable routing, grounding, shielding, and connectors.

    • Review wiring and equipment placement relative to power systems and RF sources.

  3. Measurement and Signal Capture

    • Use a spectrum analyzer and probes to scan relevant frequency ranges

    • Monitor emissions and transient activity under various load conditions

    • Determine whether the EMI is radiated, conducted, or coupled.

  4. Source and Coupling Path Identification

    • Identify the emitting device, switching edge, or parasitic source.

    • Trace how the interference reaches the victim system (capacitive, inductive, or ground return path).

  5. Root Cause Analysis

    • Correlate measured EMI to known component behavior (e.g., clock edges, VFD switching).

    • Match observed EMI to known spectral profiles (e.g., PWM noise, DC-DC converter harmonics).

  6. Mitigation Recommendations

    • Propose fixes: shielding, filtering, layout changes, grounding strategies

    • Verify effectiveness using before-and-after measurements

  7. Documentation and Reporting

    • Provide an EMI report detailing sources, affected systems, test data, and mitigation actions.

Deliverables from a Professional EMI Investigation

  • Site or system EMI scan results (frequency vs amplitude).

  • An annotated equipment layout or wiring diagram with emission points.

  • List of identified emitters, affected devices, and coupling paths.

  • Photos of test setups and measurement methods.

  • Suggested design or installation modifications.

  • Compliance standard references (FCC, CISPR, MIL-STD, etc.).

  • Post-mitigation verification results (if applicable).

What an EMI Investigation Is Not

  • It is not a full EMC certification test (though it may simulate one.)

  • It is not a guarantee of compliance, but a diagnostic tool to enable compliance.

  • EMI investigations are often reactive and expensive and are not a substitute for good design.