Most electrical/electronic designs today are subject to electromagnetic interference/electromagnetic compatibility (EMI/EMC) testing.
The first step is to write a test plan. If you are working in the defense industry, a military test plan is usually a contract requirement. If not, you’ll still want one. If you don’t know enough to create one, ask your lab to do it, or to recommend an independent consultant who can help.
A good test plan includes:
- A configuration, mode of operation, and monitoring method, which represents a worst case scenario from an EMC perspective
- Special software, test fixtures, and supporting equipment may be needed to exercise the equipment under test
- A description of hardware to be tested, including peripherals & I/O configurations
- An indication of which external power and data I/O ports need to be tested for each test method
- Required tests
- A definition of failure criteria
- How to monitor, recognize & report failures
- Special needs: Software, power, cooling, etc.
Then, get pricing and scheduling from a leading 3rd party test lab, like MET Labs.
You’ll have to determine what the lab will supply versus what you will supply. You will need:
- Equipment under test (EUT) & spares
- Cables & connectors
- Test fixture (for some programs)
- Tool kit
- EMI suppression supplies – ferrites, copper tape, etc.
- The equipment’s design or compliance engineer or someone else familiar with the product to witness testing
In the Lab
Preliminary testing (pre-testing) is always a good idea. Shortened versions of each test method can be performed to identify failures. Design modifications can be made before final testing is scheduled. A radiated emissions pre-test, often referred to as a pre-scan, is the most common pre-test performed. Even if there is no plan to perform pre-testing for the other test methods, a radiated emissions pre-scan can identify failures and allow for design modifications, which will likely cause the equipment under test to perform better for the other test methods as well.
Then run the full program as specified in the test plan. If you pass the first time, congratulations! If not, don’t take it personally – it’s not unusual, especially with early-stage pre-compliance testing. And practically anything can be overcome.
If you fail a test, do some quick troubleshooting – you may be able to fix the problem right away. Do the easy things first:
- Verify that the EUT is still working properly. This is particularly important with immunity tests that might cause damage.
- Unplug external cables to see if it improves results. External cables, although not designed to do so, act as antennas to radiate emissions and receive RF interference.
- Add ferrites to cables
- Clean mating, conductive surfaces of paint and other materials.
- Add an RF filter module at the power input to the equipment under test to limit RF emissions and protect from continuous conducted disturbances.
- Add a MOVs or other transient limiting device at the power input to protect from transient disturbances.
- To limit leakage, wrap the EUT in aluminum foil
For immunity, back off the test levels to determine the actual failure levels. If you are close, maybe a ferrite will fix things. If not, that’s good information to have – it will help you narrow the possible failure mechanisms.
Don’t be afraid to ask for suggestions. Test engineers at an experienced lab like MET will have seen hundreds if not thousands of products, and know many debug and quick-fix solutions.
MET Labs is a full-service EMC testing lab with multiple convenient locations. Contact us for a free quick-response quotation.
Most electronic devices destined for sale in the U.S. fall under Part 15 (CFR 47) of the Federal Communications Commission (FCC) rules for limits to the unintentional and intentional emission of radiation. However, there are some exemptions that you may be able to take advantage of, depending on the nature of your product. You can find the bulk of this information in Section 15.103 of the rules.
The FCC says it is “strongly recommended” that you still attempt to comply with the rules, regardless of your product type. They have the power to halt sales of your device if the device has been found to cause harmful interference, so proceed with caution.
Here is a simplified description of product types that are FCC exempt from digital emissions testing:
- A digital device utilized exclusively in any transportation vehicle including motor vehicles and aircraft. Note: wireless devices are subject to other FCC rules.
- A digital device used exclusively as an electronic control or power system utilized by a public utility or in an industrial plant.
- A digital device used exclusively as industrial, commercial, or medical test equipment.
- A digital device utilized exclusively in an appliance, e.g., microwave oven, dishwasher, clothes dryer, air conditioner, etc.
- Specialized medical digital devices (generally used under the supervision of a licensed health care practitioner) whether used in a patient’s home or a health care facility.
- Digital devices that have a power consumption not exceeding 6 nW.
- Joystick controllers or similar devices, such as a mouse, used with digital devices but which contain only non-digital circuitry or a simple circuit to convert the signal to the format required (e.g., an integrated circuit for analog to digital conversion).
- Digital devices in which both the highest frequency generated and the highest frequency used are less than 1.705 MHz and which do not operate from the AC power lines. Digital devices that include battery eliminators, AC adaptors or battery chargers which permit operation while charging or that connect to the AC power lines indirectly do not fall under this exemption.
Although not noted in section 15.103, equipment authorization is also not required for:
- Personal use home-built devices (not kit-constructed) that are assembled in quantities of five or less
- Low-frequency devices that don’t generate timing signals or pulses at a rate in excess of 9,000 pulses (cycles) per second (i.e., 9 kHz)
Note that equipment is not exempt unless all of the devices in the equipment meet the criteria for exemption. For example, if you have a specialized medical digital device with a wireless transmitter, the wireless transmitter still has to be tested.
Please confirm with MET Labs whether you are indeed exempt as there are some caveats to this information.
And, of course, FCC-exempt devices might be required to undergo other types of testing, like product safety certification for U.S. OSHA compliance or EMC testing for CE marking in Europe. Contact MET for a full evaluation of your product line and its intended markets.
In February 2014, the IEC published IEC 60601-1-2:2014, ed 4.0 for Medical EMC. There are a number of changes in the 4th edition, including new immunity and risk analysis requirements.
For new products in the U.S., the FDA will make a decision on the 4th edition this July, with a likely 3-year transition period (2017 recognition). The FDA does not currently require retesting of legacy products unless changes are made to the product that may affect its compliance.
Canada is planning to review the 4th Edition sometime in 2015 so it will not be accepted before 2015/2016. It’s typically 3 years before accepted standards are required for new submittals.
In Europe, CENELEC has voted affirmatively to accept the 4th edition but has not set a date to withdrawal (DOW) the 3rd edition. The DOW of the current 3rd Edition is expected in the 2017-2018 timeframe. There is no grandfathering in Europe.
Following are some of the key changes in the 4th edition.
Use environments are split into three areas:
- Professional Healthcare Facility Environment
- Home Healthcare Environment
- Special Environment (test levels specified in Annex E)
Small clinic, and Home use equipment need CISPR 11 Class B emission, IEC 61000-3-2 Class A harmonic distortion, and IEC 61000-3-3 voltage fluctuation and flicker. The home use equipment needs 10 V/m, 80 MHz to 1 GHz immunity.
For equipment that is installed in an aircraft or an ambulance, additional testing per ISO 7137 and CISPR 25 applies.
For an EUT with auto ranging power supply, most tests are required to be performed at one nominal voltage only. Only voltage interruptions need to be performed at maximum and minimum voltage if the rated voltage range is >25% of lowest rated input voltage.
Immunity test levels increase:
- The range of testing for radiated immunity harmonized up to 2.7GHz (up from 2.5GHz in the 3rd edition)
- Magnetic immunity at 30A/m
- Conducted immunity at 6V in ISM bands
- ESD at 8kV contact and 15kV air (up from 6kV and 8kV in the 3rd edition)
- Voltage dips and interruptions at additional phase angles
In addition to these Immunity changes:
- Immunity levels (Table 9) are harmonized with IEC 60601-1-11
- Immunity testing now follows the same port-by-port convention of the IEC 61000-6 series of Generic EMC standards
- Immunity to proximity fields from RF wireless communications equipment is now included, and is based on a minimum separation distance of 30cm
- There is a procedure for continuing to test a product that is damaged by an immunity test signal
And Risk Management is expanded:
- Manufacturers will be required to submit a test plan and the risk analysis document before testing
- Operating modes are based on risk analysis
- Reasonably foreseeable electromagnetic disturbances (Annex F) shall be taken into account in the risk management process
- The risk management process is used to determine whether subsystem testing is allowed
- The minimum separation distance are considered in the risk management process
- Reduced test levels (e.g. based on the intended use of the product) must be justified in the risk management file
Contact us for questions about these changes or for a free quote to test and certify medical equipment to any edition of 60601-1.
To sell most types of electrical or electronic products in the European Union (EU), electromagnetic compatibility compliance with EMC Directive 2004/108/EC is required.
To meet the essential requirements of the EMC Directive, testing to a particular standard or standards is voluntary, although recommended, as they can provide a presumption of conformity. Harmonized standards are featured in The Official Journal of the European Union (OJ). Each standard governs a particular type of equipment, such as laboratory, IT, or household. The standards determine the strength and the limits for tests used to evaluate the product. Engineers should use generic standards only when there is no family standard covering the product.
If a product is redesigned or if the standard expires, manufacturers can perform a gap analysis to see if the product needs to be re-tested. If not, the manufacturer can prepare documentation with justifications, explaining why re-testing is not necessary.
The directive requires all possible product configurations be included in the EMC assessment, although a worst case representative model may be sufficient to cover simpler versions. If the difference is not design-related, such as a product color or shape, this model can be excluded from the list.
A company needs to prepare technical documentation or declaration of conformity (DoC) in accordance with Annex IV. The file should include a general description, environments where it can be used, warnings, manuals, and test reports.
The following standards are a good reference on how to prepare a DoC: EN ISO/IEC 17050-1:2005 and EN ISO/IEC 17050-2:2005. CENELEC has also published a specific guide for the DoC: CENELEC Guide 16.
The directive requires manufacturers or their authorized representatives to hold the technical documentation for at least 10 years after the last manufacturing date.
To ensure that products are tested to the correct standards and are in full compliance, manufacturers might want to submit their technical file and EMC report to a Notified Body (NB) for review. If everything is in order and complete, it issues a statement of opinion to be included in the technical file.
MET Labs has been designated a Conformity Assessment Body (CAB) in accordance with the US-EU mutual recognition agreement. For the EMC and R&TTE Directives, MET can prepare Technical Construction Files and perform other Notified and Competent Body functions.
If a manufacturer tries to place a non-compliant product on the EU market, it could face penalties that range from removing the product from the market to liability for a fine and/or imprisonment.
Due to rapid growth in medical devices that incorporate RF wireless technology, on August 14 the Food and Drug Administration (FDA) released final guidance for integrating radio frequency (RF) wireless technology in medical
devices. The guidance is recommended, but not mandatory.
FDA said its recommendations cover devices that are implanted or worn on the body, and others intended for use in locations such as hospitals and clinical laboratories.
The guidance discusses issues that may affect the safe and effective use of medical devices that incorporate RF wireless technology, including electromagnetic compatibility (EMC).
The use and deployment of RF wireless technology in and around medical devices is an increasing concern because the electromagnetic environments where medical devices are used might contain many sources of RF energy, and the RF wireless emissions from one product or device could potentially affect the function of another, the agency said.
FDA says these issues should be considered for all medical devices that incorporate RF wireless technology, such as Wireless Medical Telemetry Service (WMTS); Medical Device Radiocommunication Service (MedRadio) as well as Medical Micropower Network (MNN) and Medical Body Area Network (MBAN); cellular communication chipsets; and RF identification (RFID) products.
FDA recommends that EMC be an integral part of the development, design, testing, and performance for RF wireless medical devices. Beyond FCC requirements, FDA recommends using risk analysis to identify any potential issues associated with EMC and determining risk acceptability criteria based on information about the device and its intended use, including foreseeable misuse, sources of environmental EMD (e.g., radio transmitters, computer RF wireless equipment), and the potential for RF emissions to affect other devices.
IEC 60601-1-2 is a FDA-recognized consensus standard for EMC, but it does not adequately address whether the wireless communications will operate properly in the presence of in-band EMD (e.g., other RF emissions overlapping the frequency band utilized by the medical device wireless signals). Therefore, the medical device’s wireless communication(s) should be actively transmitting while testing for susceptibility during all EMC immunity testing.
EMC considerations for active implantable medical devices are covered under documents such as the ISO 14708-1 standard (see Appendix B).
FDA worked closely with the Federal Communications Commission (FCC) to develop this guidance.
MET Labs teamed with FDA on a voluntary Program to Test Medical Devices for RFID Interference. Find out more about the Program.
MET’s Annual Global Compliance Seminar in September will include a session on Electrical Medical Equipment Approvals for EU. Register here.
China is fast becoming the largest consumer market in the world, and for many products, China Compulsory Certification (CCC) is necessary for manufacturers to tap this market.
There are three main certification bodies (CBs) for electronic equipment:
- China Quality Certification Center (CQC) – issues all electronic equipment CCC certificates
- China Information Security Certification Center (ISCCC) – issues ITE CCC certificates
- China Electronics Standardization Institute (CESI) – issues A/V CCC certificates
An application is submitted to one of the certification bodies mentioned above. Once the application is accepted, the manufacturer has samples tested at an accredited lab in China. When the product passes, the test report is issued by the test lab and reviewed by the certification body. If the CB is satisfied with the test report and the manufacturer passes an initial factory inspection, the report will be approved and the CCC certificate will be released.
The CCC certificate is generally valid for five years and requires follow-up inspections that verify quality control and product consistency.
CCC certification is to Chinese national standards called Guobiao or GB standards. Usually the GB standard is harmonized to an IEC standard. For example for ITE, GB4943 is harmonized to IEC60950 for product safety; GB17625 (updated to GB17625.1-2012 on July 1, 2013) is harmonized to IEC61000-3-2 and GB9254 is harmonized to IEC/CISPR 22 for electromagnetic compatibility. There are some minor national deviations like ratings, altitude or tropical zone requirements. (Read more about recent changes to GB8898 Audio, Video and Similar Electronic Apparatus – Safety Requirements and GB4943.1 Safety of Information Technology Equipment.)
Generally, if you can pass the IEC standard, you should be OK to pass the CCC test. Manufacturers can save time and reduce cost by transferring a CB report to a CCC report.
MET Labs has experience helping manufacturers obtain CCC certification. MET’s China operations are based in Shenzhen, Guangdong Province. Contact MET China or MET U.S. for more information about CCC certification.
Early Consideration of EMC & Product Safety Compliance in Product Development Saves Time and Headaches
When developing a new electrical product, early consideration of electromagnetic compatibility (EMC) and product safety compliance issues will pay major dividends later.
If compliance is not engineered in from the start, expect to endure this pain:
- A major delay as the product is redesigned, jeopardizing time to market and product viability
- Significant extra costs for rework and increased product cost
- Team dissension and rock-bottom morale
What’s the best way to integrate compliance into a new product? First, get buy in from senior management, then:
- Buy and read the relevant safety and EMC standards and train your design engineers in the basics of compliance
- Have your compliance engineers work side by side with the designers, providing deeper expertise when needed, and information about the latest changes to standards and regulations
- Perform early design reviews and early testing on the first prototypes to lower the risk during final compliance testing
Don’t have a compliance engineering team? We can help. In addition to testing and certification, MET Labs offers compliance assistance, with controls in place to prevent a conflict of interest, as required by our accreditation agencies.
The Compliance Today blog for electrical product manufacturer compliance engineers saw a significant jump in readers and subscribers in 2012. Following were the most popular 2012 posts, by pageviews.
- RTCA/DO-160G is Latest Version for Testing of Airborne Equipment, But Not the Only Choice
- UL1604 to Be Replaced by ANSI/ISA 12.12.01-2000 for Hazardous Locations Certification
- 2011 National Electrical Code (NEC) Updates Standard for the Safe Installation of Electrical Equipment
- Health Canada Provides Guidance on IEC 60601-1 3rd Edition Transition
- Product Safety Compliance Engineers Use These Resources
- IECEE Suspends Brazil NCBs and CBTLs from CB Scheme
- Electromagnetic Compatibility Compliance Engineers Use These EMC Resources
- China CCC Product Safety Compliance for A/V & IT Equipment is Changing
- For IT Equipment in Canada, ICES-003 Issue 5 Required by August 2013
- Military EMC Testing Standard MIL-STD-461G is Coming
If you want to receive an email of each post when it publishes (about once a week), subscribe on the right side of this page.
Want more in-depth information on one of these topics? Check to see if we are planning a seminar or webinar on it.
Need electrical product testing? Fill out an RFQ.
We received so much positive feedback on our blog posts for EMC Compliance Links and Product Safety Compliance Links, that we decided to dedicate a post to spotlight the top blogs for electrical product developers.
With a few exceptions, these blogs are from independent sources, like industry associations, publishers or consultants. What are we missing? Leave a comment with a link to it.
Aerospace & Defense Blog Military and aerospace electronics news and information.
ANSI International standards and accreditation activities.
Buzzblog Intelligence and insight for Network and IT Executives.
CertAssist Consulting Product Safety information, especially regarding 60950-1 and 61010-1.
Circuit Advisor Circuit design and troubleshooting.
Compliance Today Electrical testing and certification news and information.
DfR Solutions Forum Reliability design and testing.
Digital Dialogue From the Consumer Electronics Association, sponsor of the Consumer Electronics Show. (Side note: You can meet with MET at CES next week)
EDN Network 59(!) blogs for the electronics community on various topics.
EE Life Blog Electrical engineering topics from EE Times.
EleBlog Frequently updated blog on the electrical industry.
Electronics Weekly Blogs 15 blogs, including Certification & Test and Directive Decoder.
EMC Zone Issues affecting engineers working in the EMC industry.
Emergo Group Global medical device regulatory updates.
EPN Automotive Electronics Blog Automotive electronics issues from a European perspective.
EPN Industrial Automation Blog Industrial automation and controls topics from a European perspective.
EPN Renewable Energy Blog Info on electronic components and technologies related to solar power, wind power, and other renewable energy sources from a European perspective.
EPN RF & Wireless Blog Updates on RF/microwave and wireless technology, systems, standards and events from a European perspective.
IEEE Spectrum 5 blogs on nanotech, robots, risk analysis, general tech, and energy.
IEEE Standards Insight Promotes technology standards and their development.
Instruments for Industry Information to help RF EMI and EMC test engineers, from an amplifier manufacturer.
Medical Electronics Design A resource for medical electronics OEMs.
Microwave Journal A handful of blogs concentrating on microwave and RF technology.
NEMA Currents Information on electrical grid, safety, energy efficiency, smart grid, and regulation.
Nick’s Fire, Electrical Safety & Security Blog Common sense security, fire & electrical safety.
OnSafety Official blog of the U.S. Consumer Product Safety Commission.
Pradeep’s Point A resource for semiconductors, solar PV, telecom, electronics, infocom, components, nanotech, and IT.
Product Safety Blog Product safety legal issues from Miles & Stockbridge.
Regulatory News Blog Telecom regulatory news.
Reliability Blog Electronics reliability engineering.
RFID Journal Blog RFID industry news and information.
Smart Grid Sherpa Information on smart grid technologies, from DNV KEMA.
Test and Certification Blog Product test and certification from an EU perspective.
Test & Measurement World 14 blogs, including The EMC Blog and Eye on Standards.
WeMakeItSafer Product safety regulations and recall information.
What are your favorite electrical product development blogs? Please leave a comment with a link to it.
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In the event of a power failure on the electric grid, it is required that any independent power-producing inverters attached to the grid turn off in a short period of time. This prevents the DC-to-AC inverters from continuing to feed power into small sections of the grid, known as “islands.” Powered islands present a risk to workers who may expect the area to be unpowered, and they may also damage grid-tied equipment.
A single inverter operating independently can easily detect the presence or lack of a grid source. However, if there are two inverters in a given island, things become considerably more complex. It is possible that the signal from one can be interpreted as a grid feed from the other, and vice versa, so both units continue operation.
Since 1999, the standard for anti-islanding protection in the United States has been UL 1741, harmonized with IEEE 1547.
The requirement for a unit under test is to detect an island condition and cease to energize the area electric power
system (EPS) within two seconds of the formation of an island. This disconnection time is measured from the point that the switch is opened up disconnecting the grid but leaving the islanding circuit connected and the point that the unit ceases exportation of current to the grid.
The island load is adjusted to ensure a power quality factor (Q) of 1.0 (+/- 0.05) and the “central” balanced load condition. In addition, the output current flowing to the grid through the switch (S3) is limited to a maximum value of 2% of the rated output current and the Q=1.0 balanced load condition of the unit under test.
In addition to testing at the balanced load condition of Q=1.0, The test is to be repeated with the reactive load (either capacitive or inductive) adjusted in 1% increments from 95% to 105% of the initial balanced load component value. If the unit’s shutdown times are still increasing at the 95% or 105% points, additional 1% increments shall be taken until trip times begin decreasing.
The anti-islanding test is repeated for 3 output power levels: 33%, 66%, and 100% of the rated output power of the unit under test.
The test is considered complete when one of two situations occur:
- When disconnect times illustrate a pattern of decreasing times with respect to a balanced load condition yielding the longest disconnect time
- When the resultant tank circuit frequency is such that it is past the frequency trip point of the unit under test such that the unit under test is tripping offline due to a frequency fault
UL 1741 has other performance requirements as well, including power quality, interconnect integrity, and operating voltage and frequency parameters. For information about testing inverters to any of these requirements, contact us.