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Prescreening Devices to Ensure EMC Compliance (the First Time Around)

Testing electrical and electronic devices for EMC compliance can be a daunting task. With few local testing labs available, companies will often have to travel to find a certified testing lab that is equipped to assess their specific product. And due to the lack of available labs, companies often have to book testing sessions in advance and follow an unforgiving, strict schedule. The thought of EMC testing gives engineers a headache, but the thought of failing testing and having to repeat the process a second or third time is even more frustrating. For medical device engineers, whose standards are much stricter than other device standards, testing for EMC compliance is a bit of a nightmare. There is, however, a way to speed up the process of EMC testing while keeping costs low: prescreening devices for EMC compliance.

Before we discuss prescreening tactics for medical devices, we should define EMC testing and explain its significance.

EMC (electromagnetic compatibility) is the ability of electrical and electronic equipment to function without interference from or to another piece of electrical or electronic equipment. Interference (EMI) disturbs electrical circuits, causing them to malfunction or stop working completely. In the medical field, ensuring that devices are not susceptible to such interference is imperative, as such interference could potentially harm or kill someone.

When testing for EMC compliance, specialists with perform two types of tests: emissions testing and immunity testing. Emissions testing measures interference coming from the device being tested. Immunity testing measures a device’s immunity to surrounding interference.

According to a study, 50 percent of products fail EMC testing the first time around. Depending on the product’s complexity, it can cost thousands of dollars for each testing session, not to mention the cost of redesigning the product (sometimes from scratch) and delaying its to-market schedule. According to this same study, these products fail the first time around due to a lack of knowledge of EMC principles; the failure to incorporate EMC principles into the design cycle; the application of erroneous EMC regulations; unpredicted interactions between circuit elements; and the incorporation of non-compliant modules into the final product.

To reduce the cost of failure, engineers should incorporate EMC design principles into their product design. You can find various articles on how to do this on our blog. Yet, no matter how well-designed, sometimes products don’t work out the way we intend. Human error, environmental factors, and other things can prevent devices from meeting required standards. Therefore, to ensure that your product has a higher chance of passing EMC compliance testing the first time around, you should invest in prescreening equipment.

Prescreening equipment is equivalent in cost to EMC testing. A comprehensive testing set, such as Hameg’s EMC-PCS3 instrument kit, costs around $7,000. While this price seems a bit high, it beats the cost of having to retest products with a testing lab. Engineers can also build their own EMC testing equipment. If taking this route, you’ll need the following equipment to prescreen:

  • Emissions Testing:

    • Magnetic Field Probe: finds signals from alternating currents that flow in nearby conductors

    • Electric Field Probe: finds mode voltages in circuits, cables, and chassises

    • Conducted Emissions Probe: assesses conducted emissions

  • Immunity Testing:

    • Signal generator attached to the above probes: tests immunity

    • Oscilloscope (or an RF receiver used in combination with software): tests immunity

For the best results, engineers should conduct small tests throughout the design cycle. Prescreening is a relatively easy and quick way to tell if your design needs to be tweaked. They typically take one day; engineers can test, tweak, and retest within a short amount of time. By taking one day to perform this test every so often throughout the design cycle, you can save your company thousands of dollars as well as time. If you need a local EMC testing lab, contact Rhein Tech Laboratories today. We’re conveniently located in Herndon, Virginia. Rhein Tech offers EMC testing in accordance with the standards for EMC (emissions and immunity), Radio, Military and Defense Aerospace, Industrial, Medical and Scientific, Electrical Safety, and Radio Frequency Hazard. In addition to this, we also provide:

  • On-Site testing at client premises when the equipment is too large or cannot be configured in a laboratory setting

  • Radio Frequency Site Surveys to determine sources of interference or when a low radio frequency ambient site is required

  • Shielding effectiveness testing for various materials

  • EMC testing for compliance to the rules, regulations, and standards of the FCC and ISED Canada.

Are you wondering if you should switch to Rhein Tech? We offer last minute scheduling and flexibility, which other labs don’t offer. And if, even after prescreening, your device does fail EMC compliance testing, we won’t fail you. Instead, our design engineers will work with you to solve EMI issues. Sounds great, right? We take the headache out of EMC testing, so contact us today for a quote! Sources:,

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