The Best Value in Electronic Test Measurement Precompliance

The Best Value in Electronic Test & Measurement

Pre-compliance Basics How to get through compliance quickly

What is EMC Testing? EMC = Electromagnetic Compatibility Moving electrons create electromagnetic waves For an intentional radiator (radios, Wi. Fi, etc. ) these are desirable. . But. . Unintentional radiators: • The waves interfere with other intentional radiators or cause issues (jamming, lock up, failure). . This undesirable radiation is known as Electromagnetic Interference (EMI) Governments regulate the amount of EMI allowed (RF or other) • Guidelines in the US are created and enforced by the FCC (Federal Communications Commission) Compliance is self-determined… but the testing can be complex. End result – you have to rely on special test houses (Compliance Labs) to perform the required testing.

Basic EMC tests • Radiated Emissions – How much RF is flying off of a product • Conducted Emissions – How much RF is sent back down the power line • Susceptibility - How much RF can your product take before failure

Radiated Emissions • Must isolate the DUT from the environmental RF • Open air or special chamber (anechoic or semi-anechoic) = $$ • Physical and electrical test setup is critical • Averages $2000/day. . for testing. Consultation can cost more

Radiated Emissions Basic Setup

Radiated Emissions: Pre-compliance Difficult without a chamber, but possible • Consistent, repeatable, and well understood environmental RF (background scans) • Physical layout should not change (people, equipment, desks, etc. . ) • Reflections (Hot/cold spots) should be understood Still relative measurements. . So, you can get meaningful data. . • Use a fixed physical layout (measured distances and angles), pictures of the tests, etc. . • Perform an environmental RF test immediately before and after DUT testing (DUT off) • If you have a failed test report, you can use this to help “key in” on specific frequencies

Near field probes Near field = close proximity measurements Far field measurement antennas ~ 1 m or more away from DUT Near field ~ an inch or two • Magnetic (H) and Electric (E) field probe types • Can ignore environmental effects due to weak coupling • Simple setup • Fixturing can minimize variations and make better relative measurements • Can use with a failed report to help find root cause of issues

Near field probes

Current clamp • Cabling can radiate and cause failures. . Especially poorly shielded cables • Can make relative measurements using a current clamp

Conducted Emissions • Measures DUT energy directed towards the power grid • Interference on power lines causes AM radio interference • Much more repeatable than radiated. . And easier

Susceptibility • Irradiate DUT and check performance • Must shield to prevent exceeding FCC regulations for unlicensed transmissions • Can use near field probes to inject signals onto boards and traces

Tools • Spectrum analyzer – The “eyes” of the EMC Engineer • Oscilloscope with FFT • Sequencing software • Near field probes • Antennas (rabbit ears and bowties can be useful in some situations) • Current clamps • Aluminum foil • Conductive tape • Line Impedance Stabilization Network (LISN) and transient limiter • RF Source with AM modulation capability probe can easily find leaks • AM Radio (can be used to troubleshoot radiated issues)

SIGLENT Tools • SIGLENT SSA 3021 X/32 X – 2. 1 GHz/3. 2 GHz Spectrum analyzer (Start at $1395) • SIGLENT SVA 1015 X – Spectrum and vector network analyzer (Start at $1395) • Easy. Spectrum software (free) • SIGLENT SDS series of scopes (Start at $299) • SRF 5030 and SRF 5030 T near field probes • More to come…

Common failure root causes • Harmonics- What is the rise time of digital signals within your enclosure? Faster rise times = higher frequency harmonics = potential for trouble • Shield terminations on connectors – Are they really shielded 360°? Small common mode currents (a few u. A) can radiate. . And will find an antenna • LCDs – Rarely shielded well and have high data rates • Unintentional antennas (cutouts/holes are physically identical to “solid” antennas) • Splits in ground planes. . time varying currents follow path of least impedance, not just resistance. . • Control current return paths, or the electrons will find their own way “home” • Enclosure shielding/gasketing – Nearfield probe can easily find leaks

Resources Application Notes: • Pre-compliance basics: https: //www. siglentamerica. com/application-note/electromagnetic-compliance-pre-compliance-test-basics/ • Pre-compliance Near Field: https: //www. siglentamerica. com/application-note/electromagnetic-compliance-troubleshooting-near-field-current-probes/ • Pre-compliance Conducted Emissions: https: //www. siglentamerica. com/application-note/electromagnetic-compliance-pre-compliance-conducted-emissions-testing/ • Easy. Spectrum software: https: //www. siglentamerica. com/operating-tip/getting-started-easyspectrum-software/ Books: • EMI Troubleshooting Cookbook: Andre’ and Wyatt • Electromagnetic Compatibility Engineering: Ott

Resources, con’t Useful sites: FCC subpart 15 limits: www. fcc. gov The EMC Blog: https: //www. edn. com/electronics-blogs/4376432/The-EMC-Blog Ken Wyatt: https: //www. emc-seminars. com/ Doug Smith: http: //emcesd. com/bcsem_emcweek. htm IEEE EMC Society: http: //www. emcs. org/

Thank You SIGLENT—The Best Value in Electronic Test & Measurement Contact Info www. siglentamerica. com Email：info@siglent. com Tel： 440 -398 -5800 Company Address 6557 Cochran Rd Solon, OH 44139