What Is an EMI Investigation?

When electronics misbehave and no one can say why, electromagnetic interference is often the cause. An EMI investigation is how we find it. We locate the emission, work out how it reaches the equipment it's disrupting, and fix the problem at its source so the system runs reliably, passes compliance.

What We're Trying to Learn

Every investigation answers the same core questions. Where is the interference coming from? How does it get from the source to the victim, through conductors or through the air? What does it look like in frequency, amplitude, and mode (common or differential)? And what is actually wrong: a design flaw, a grounding problem, a shield that isn't doing its job, or inadequate filtering? Once we have those answers, the problem can be fixed properly instead of guessed at.

Signs You May Need One

Clients usually call us after something has already gone wrong. Equipment resets, locks up, or behaves erratically. A product fails FCC, CE, or CISPR emissions testing. A communication link drops or corrupts data. A medical or scientific instrument gives noisy or unstable readings. Lights flicker, speakers hum, or radios pick up interference. Ground loops or stray currents damage equipment, or power quality suffers from harmonics and transient spikes.

How We Work

We start with the symptoms. We need to know exactly what fails, under what conditions, and when it happens: at startup, under load, or seemingly at random. Intermittent problems almost always have a pattern once you look closely enough.

We look before we measure. A careful inspection of PCB layout, cable routing, grounding, shielding, and connectors often points toward the likely culprits. So does the placement of equipment relative to power distribution and RF sources.

Then we measure. Spectrum analysis and probing across the relevant frequency ranges, under different operating and load conditions, tells us whether the interference is radiated, conducted, or coupled. It also captures transient events that come and go.

We trace the path. That means identifying the emitter, whether a switching edge, a clock, or a parasitic resonance, and following the interference through capacitive, inductive, or ground-return coupling to the point where it does damage.

We find the root cause. We match what we measured to how real components behave. PWM noise, VFD switching, and DC-DC converter harmonics each leave recognizable signatures.

We fix it and prove it. Mitigation may involve shielding, filtering, layout changes, or a revised grounding scheme. We measure again afterward so the improvement is documented, not assumed.

What You Receive

You get a written report covering what we found and what we did about it. It includes:

• EMI scan data (frequency versus amplitude).

• A list of emitters, affected equipment, and coupling paths.

• Photos of the test setups.

• Recommended design or installation changes.

• References to the relevant standards (FCC, CISPR, MIL-STD, and others).

• Post-mitigation verification data where applicable.

What It Isn't

An EMI investigation isn't a full EMC certification test, although we can run measurements that approximate one. It isn't a guarantee of compliance either; it's the diagnostic work that makes compliance achievable. It is also no substitute for good design. Investigations are usually reactive, and fixing a problem after the fact costs more than designing it out from the start.

We genuinely enjoy this work. Tracking down a problem that has stumped everyone else is deeply satisfying, and it's a big part of why Elexana is an award-winning company.

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