Fortunately, there is a happy middle ground that significantly reduces the risk of failing EMC compliance testing. For a fraction of the cost of a full test facility, design teams can acquire everything necessary for pre-compliance checks. Modern software tools greatly simplify test set-up and analysis so even non-RF experts can gain meaningful insights.
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In later development stages, pre-compliance testing can catch compliance problems and improve the chances of passing EMC compliance testing on the first try. The goal of pre-compliance testing is to mimic the compliance-test set-up well enough to uncover potential problems. Pre-compliance testing does not require test equipment identical to that for compliance testing. It typically involves a spectrum analyzer with a quasi-peak detector, a preamplifier optional , an antenna with a non-metallic stand for radiated emissions, a line impedance stabilization network LISN for conducted tests, a power limiter for conducted tests, near-field probes for diagnostics optional , and an oscilloscope with frequency and time correlation capabilities to assist in debugging optional.
The latest USB-based spectrum analyzers offer general-purpose filters and detectors to support pre-compliance testing and for troubleshooting any EMI issues. Pre-compliance testing can employ fast measurement techniques intended to give a quick look at problem areas. The test site is usually temporary. When selecting a site, it is best to pick a location with an electromagnetic environment as free as possible from external signal sources. Other considerations that improve measurement accuracy include having a good ground plane and minimizing the number of metal objects near the test area.
The ambient noise is the teal trace and the peak scan is the yellow trace. The table shows the results of peak scan versus the limit line. The results in this example show numerous spurs in the A region as well as a failure. The next scan uses quasi-peak detection across region A zoomed up to 59 MHz for more precise results. This technique is more in line with the official testing done at an accredited test house.
The figure at right shows the results for peak green trace and quasi peak yellow trace versus the limit line. In this example, the device now passes with a margin of 1. However, this is probably not enough to ensure the device will pass real compliance tests at the test house. Standards documents spell out the setups for radiated compliance tests. Developers running their own tests try to mimic these setups as closely as possible.
In setting up radiated testing, there are several challenges.
Why You Should Consider EMC Compliance and EMI Countermeasures Early in Your Design
The emissions tend to be directional. To address this, a test lab will typically vary the height of the receiving antenna between one and four meters, and it will rotate the EUT on a turntable. The receiving antenna picks up both the signal direct from the EUT, as well as reflections from the ground. Additionally, the floor should be covered with an electromagnetically reflective surface aluminum, steel, wire mesh, etc. And the ground-plane area should be relatively flat. The books listed below cover topics of interest to EMC engineers.
Books without an active link may be out of print; however many of them can still be obtained through the booksellers listed at the bottom of this page. ISBN: IISBN: Sengupta and Valdis V. Walker , Artech House, ISBN Welker, R. Nagarajan and Carl E. Scott Bennett , John Wiley and Sons, Controlling Conducted Emissions by Design J. Fluke , Springer, Smith, Jr. Coupling to Shielded Cables E. Vance , Krieger, Keenan , The Keenan Corp. Gnecco , Sci-Tech Publishing, Duff , Elsevier, Terrell and R.
Wiley-VCH - Testing for EMC Compliance
Keenan , Newnes, Electromagnetic Compatibility J. Goedbloed , Prentice Hall, Weston , CRC Press, Electromagnetic Compatibility Design Guide E. Freeman and M. Sachs , Artech House, Electromagnetic Compatibility Engineering H. Ott , John Wiley and Sons, Electromagnetic Compatibility Handbook Kenneth L. Kaiser , CRC Press, Electromagnetic Compatibility Handbook N.
Violette, D. Our labs and equipment use the latest technology and are powered by the most respected and experienced engineers and technicians. We have people, processes, tools and knowledge capabilities that allow us to test to extreme limits and complex standards. These events occur when a user touches the device and another metallic surface at the same time.
EMC Compliance Testing
Harmonic frequencies greater than 50 Hz and voltage dips in the 5 to 15 Hz range can cause harmful interference for electronic devices. Devices need to be tested under these conditions to meet EMC compliance. Electrical fast transients testing EFT simulates a common type of real-world interference which was previously neglected. EFTs involve a high-frequency disturbance on a power line which occurs as a result of inductive loads being turned on or off.
- Getting products through EMC/EMI compliance tests.
- The Benefits of Pre-Compliance EMC Testing!
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Testing for voltage dips and interrupts VDIs involve simulating the conditions of voltage dips and voltage interruptions. The device is tested in the simulated environment to assess tolerance against VDIs. Surge testing is a key part of EMI analysis. NTS produces a low frequency, high energy electrical transient to simulate the effects of a lightning strike on a nearby power line. Military and Aerospace applications commonly require radiated susceptibility tests. High intensity radiated fields HIRF are divided into three frequency bands.
Each of these bands can affect airplane electronics in various ways:. HIRF certification generally involves measuring transfer functions to estimate the potential effects of EMI on an aircraft.
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NTS employs a variety of tools and techniques to produce accurate testing that is fully compliant with all required specifications. NTS has lightning simulation capabilities that include:. We can precisely measure direct and indirect effects of a lightning strike. To simulate these conditions, NTS facilities have a series of high current generators and an indoor test area that measures 40 x feet.
A lightning strike can also create a temporary rise in earth voltages after an impact.
This indirect effect creates an intense electromagnetic field that can harm equipment up to a radius of one kilometer. NTS can run a variety of tests, including pin injections, transformer injections, and field immersions to determine the indirect effects of lightning. Together, these tests allow our engineering team to perform a thorough field and transient analysis. This further allows us to assess the indirect effects of a strike on everything from individual circuit parts to complex interconnected electronic systems.
We regularly service the needs of military contractors, avionics manufacturers and more. Our experienced program managers and veteran engineers work closely with you to meet your EMC pre-compliance needs from conception, design and development to final test and production. With more than 50 years of experience, NTS has a long list of satisfied clients in our portfolio.
Clients include organizations like Boeing, Cisco, U. Contact us today to learn how we can help your business. The Benefits of Pre-Compliance EMC Testing November 20, One of the biggest product development challenges today is ensuring electromagnetic interference is optimally controlled.