B Duncan Ltd
EMC Pre-Compliance Testing
Catch EMC problems in development, before they become certification failures or costly redesigns.
Emissions
Emissions analysis
Identifying and reducing unwanted electromagnetic emissions.
Conducted Emissions
- Measure unwanted electrical noise conducted along power and signal lines.
- Power both DC and AC equipment from a LISN to get standardized source impedance.
Radiated Emissions
- Measure common-mode current on cables and shields with an RF current clamp, 30 MHz to 250 MHz.
- Near-field magnetic and electric probing to locate the emitting component or track on a PCB.
- Screening and source location. Not a chamber measurement in dBuV/m, and not a substitute for one.
Immunity
Immunity testing
Testing product behaviour under common electromagnetic disturbances.
Surge Testing
- Assess the ability to withstand high-energy voltage spikes.
- Simulate events like lightning strikes or power grid switching.
Ring Wave Testing
- Simulate oscillatory transients in power lines due to switching.
Electrical Fast Transient (EFT) Testing
- Conducted EFT
- Simulate fast transient bursts on power lines to IEC 61000-4-4.
- Stepped levels, typically 500 V, 1 kV, and 2 kV.
- Capacitively Coupled EFT
- Introduce transients onto signal lines without direct connection.
- Evaluate the robustness of communication interfaces (USB, CAN, Ethernet, RS232, RS485).
Electrostatic Discharge (ESD)
- Contact Discharge
- Simulate direct ESD events to conductive surfaces.
- Air Gap Discharge
- Evaluate how your product withstands ESD events through the air.
- Test non-conductive surfaces for ESD susceptibility.
Communications
Communications testing
Communication failures are often EMC problems on signal lines rather than faults in the hardware itself.
Interface Immunity
- Capacitively coupled EFT and common-mode injection on USB, CAN, Ethernet, RS232, RS485, and PROFINET.
- Find the level at which an interface starts failing, not just whether it passes.
- Assess susceptibility without direct connection to the circuit under test.
Signal Integrity & Network Diagnostics
- Identify noise sources causing data errors, dropped packets, or intermittent link loss.
- Measure interference conducted along cables and signal lines.
- Industrial network diagnostics including PROFINET and fieldbus systems.
- Assess susceptibility to noise from nearby equipment or shared power supplies.
Problems
Problems we work on
A compliance lab reported a failure without a cause
Test houses report the frequency and the level. Diagnosis is generally outside their scope. We reproduce the failure on our bench, locate the emitting component, and work through fixes with you.
The product passes with little margin
A 2 dB margin is not a reliable pass. Unit-to-unit variation, a different cable, or a component change at the next production run will move it. We quantify the margin and identify what is consuming it.
A switch-mode supply or motor drive is the suspected source
Switch-mode supplies and inverters are the most common sources we find. Switching frequency, layout, filter placement, and cable dressing all move emissions.
Interference is causing data errors
Dropped frames on CAN, PROFINET, or RS485 correlating with a contactor closing or a drive ramping. These present as software faults and are usually EMC problems on the signal lines.
The design is not yet frozen
Emissions problems found before layout is committed are resolved in the design. Found after certification, they are resolved in a re-spin.
There is only one prototype
Immunity testing is destructive by design. We agree the levels to stop at before starting, which gives usable margin data without losing the hardware.
Why us
Why choose us
Full test capability
Emissions, immunity, communications, power supply, and investigatory testing under one roof.
Lab & on-site
We test at our Auckland laboratory or travel to your facility. The same methods apply either way.
Industry standards
All work aligns with IEC 61000 Series, CISPR 32, and FCC Part 15 as applicable.
Clear reporting
Written reports covering procedures, results, and recommendations for every engagement.
Independent & impartial
Our findings stand up to scrutiny for certification bodies, insurers, and legal proceedings.
Process
How it works
1. Initial evaluation Tell us what you’re testing, where it needs to work or sell, and where you are in the design. We confirm which tests are relevant and what a first session covers. If a lab has already tested it, send us the report.
2. Screening The product goes on the bench and is measured against the applicable limit lines. The output is the margin at each frequency of interest, not a pass or fail.
3. Root cause Where something exceeds or sits close to a limit, we isolate the source. Subsystems are disconnected one at a time, near-field probing narrows it to a component or track, and cable current measurement shows what is carrying the energy out.
4. Fixes and validation We work through the fixes with you, then re-measure to confirm the change did what was intended.
FAQ
Common questions
What is EMC pre-compliance testing?
The same emissions and immunity tests a certification lab runs, performed earlier in development while the design can still be changed. It is diagnostic rather than certifying: the purpose is to find and resolve problems before a formal booking.
What is the difference between emissions and immunity testing?
Emissions testing measures what your product puts out, to confirm it will not interfere with other equipment. Immunity testing measures what your product can withstand, to confirm it keeps working when something else interferes with it.
What does a LISN do?
A Line Impedance Stabilization Network presents a standardized, known impedance to the product under test and separates its emissions from whatever is already on the mains. Without one, you are measuring your building’s electrical noise as much as your product’s.
Why not go straight to a compliance lab?
You can, and for a mature design that has passed before, that is often the right call. For a new design, a failed booking costs the fee, the redesign, and the schedule slot, and the report will tell you the frequency but not the cause.
Do you certify the product?
Certification itself is issued by an accredited body. Our role is to get the design into a state where it passes, and to tell you where a pass looks marginal.
Can you help if we have already failed?
Yes. Send us the lab report. We reproduce the failure, find the source, and work through fixes with you.
What do we get at the end?
A written report with the test conditions, the measurements, what passed, what did not, and specific recommendations. Written to be read by your engineers and usable with your certification lab.
Related services
Other services you may need
Pre-compliance testing often goes hand in hand with fault investigation. If you’re dealing with an existing problem in the field rather than a development issue, that is where to start.
Electrical System Diagnostics
Where pre-compliance testing finds problems during development, electrical system diagnostics finds the cause of faults on installed, operating equipment. If you have an intermittent failure, VFD interference, or an earthing issue that others haven’t been able to explain, this is the service for it.
Electronics Design
EMC and thermal considered from the schematic stage, so compliance is designed into the board rather than debugged later.
Motor Control
Motor drives are among the harder products to get through EMC; we develop the drive firmware and test its emissions in the same lab.
Discuss a pre-compliance test
Tell us the product, the market it has to sell into, and your timeline. We’ll confirm which tests apply and what a first session covers.