EMC TESTING
EMI: E
find & fix problems early
xperts in EMI from Keysight Technologies have updated the application note, Making Conducted and Radiated Emissions Measurements, which will help users evaluate EMI before final compliance
verification. The step-by-step guide helps you to identify key issues, create a methodology/test system for conducting EMI measurements and more. Electromagnetic interference (EMI) compliance
testing can be a bottleneck in product development. To ensure successful EMI compliance testing, pre- compliance testing should be added to the development cycle. In pre-compliance testing, the electromagnetic compatibility (EMC) performance is evaluated from design through to production. Pre-compliance measurements are intended to
give an approximation of the EMI performance of the EUT (equipment under test). The cost of pre- compliance testing is a fraction of its full compliance counterpart using an expensive facility as the environment for it is usually less controlled. Many manufacturers use EMI measurement
systems to perform conducted and radiated EMI emissions evaluation prior to sending their product to a test facility for full compliance testing. Full compliance
measurements require the use of a receiver that meets the requirements set forth in CISPR16-1-1, a qualified open area test site or semi anechoic chamber and an antenna tower and turntable to maximize EUT signals. Great effort is taken to get the best accuracy and repeatability. These facilities can be quite
expensive. In some specific cases, the full compliance
Getting products to market on time and within budget is critical to business success. Failing electromagnetic interference (EMI) compliance testing can lead to release delays and additional design costs
❱❱ EMI measurement systems (above) can be used within the product development cycle(below) to improve outlook for full compliance testing results
receiver can be replaced by a signal analyser with the correct bandwidths and detectors as long as the signal analyser has the sensitivity required. The equipment used in systems for pre-
compliance measurements is simpler: signal analyser with N6141C EMI measurement application, line impedance stabilisation network (LISN), transient limiter and antennas. To isolate problems after they have been identified, close field probes are used. The more attention to detail in the measurement
area, such as good ground plane and a minimal number of reflective objects, the better the accuracy of the measurement. Conducted emissions testing focuses on unwanted
signals that are on the AC mains generated by the EUT. The frequency range for these commercial measurements is from 9kHz to 30MHz, depending on the regulation. Radiated emissions testing looks for signals broadcast from the EUT through space. The frequency range for these measurements is between 30MHz and 1GHz and, based on the regulation, can reach 6GHz and higher. These higher test frequencies are based on the highest internal clock frequency of the EUT. This preliminary testing is called pre-compliance testing. Unintentional radiators include TV broadcast
receivers, FM receivers, cable system terminal devices, personal computers and peripherals and external switching power supplies. Unintentional radiators are then again divided into Class A devices that are used in industrial, commercial or business environments and Class B devices that are marketed for use in a residential environment. The pre-compliance measurement process is fairly
straightforward. However, before making measurements on your product, some preliminary questions must be answered: nWhere will the product be sold (for example, Europe, United States, Japan)? nWhat is the classification of the product? ❏ Information technology equipment (ITE) ❏ Industrial, scientific or medical equipment (ISM) ❏ Automotive or
communication ❏ Generic (equipment not
found in other standards)
nWhere will the product be used (for example home, commercial,
light industry or heavy industry)? In the European requirements,
there is an additional focus on product immunity. The level of electric field that a receptor can withstand before failure is known as product immunity. EE
❱❱ To read more on EMC testing online, scan the QR code or visit
https://goo.gl/CwPm7g
32 /// Environmental Engineering /// March 2018
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