Introduction to EMI Testing
Today’s global marketplace demands that quality and reliability objectives be met. EMI testing helps provide that reliability. At Midwest EMI Associates, we offer the full range of EMI and ESD (electrostatic discharge) testing, and our chief engineer is NARTE-certified. Our laboratory has the most advanced test equipment commercially available. In a matter of a few hours, your device can be completely characterized. Our staff has the design experience necessary to help you correct any deficiencies which may be found by the testing procedure. We provide you with a detailed test report on our findings.
We are associated with Nemko, so we can assist you in determining applicable test requirements and in ensuring that your products meet the stringent testing requirements of the European marketplace. In addition to our testing services, we also provide consultation in RF design optimization and specialize in the field of medical electronics.
Electromagnetic Interference (EMI) describes a wide range of environmental electrical disturbances which can adversely affect the performance of electrical equipment.
There are several types of EMI, including conducted line interference, radiated interference, transient interference,
ambient interference and electronstatic discharge (ESD).
Electrical noise is subdivided into four categories:
- Gaussian noise: similar to the sound of static from a TV set tuned off of a commercial channel. It is a flat level of noise that can be measured with a spectrum analyzer.
- Impulsive noise: Similar to Gaussian noise, except its level is not flat but varies rapidly with time.
- Broadband noise: a measurement of noise in a particular bandwidth of the spectrum analyzer, usually 1 Mhz.
- Narrowband noise refers to signals that are “continuous” such that they only exist at particular frequencies.
Magnetic fields are directly related to electrical fields and are analyzed separately using the same techniques.
RF Design Consulting
Many of the same instruments used for EMI testing can also be used for the optimization of RF and communications circuits. The potential for RF interference increases with circuit complexity. Unwanted interference can be minimized through the use of EMI testing, resulting in optimum circuit performance. The laboratory at Midwest EMI has five high-performance computer-controlled spectrum analyzers, a network analyzer, five wideband signal generators, TWT amplifiers, and a tracking generator, a wideband signal generator, and a variety of antennas and other equipment, all of which are calibrated to ANSI standards. We can also write software to coordinate the test equipment for specific tests and have extensive experience in RF and microwave design methods.
Because medical devices are highly regulated and typically have lengthy product development cycles, it is advantageous to harden medical electronic designs against EMI early in development to design in safety and compliance. Our staff is expert in hazards analysis, failure mode and effects analysis (FMEA), design reliability, shielding, and obtaining regulatory approval. Our staff is well versed in safety regulations such as the EN 61000 series of tests and the Safe Medical Devices Act of 1990, which are significantly more stringent than previous guidelines and require a high degree of expertise to interpret.
Your customers expect safe and reliable performance from your products. Why not give then the advantage of superior performance and better value by utilizing our specialized facilities and a team of experts? At Midwest EMI, our business is providing you with the best testing and design experience available to help you provide your customers with the highest quality products.
History of EMi Testing
EMI testing arose as a result of World War II and the recognition of the fact that the detonation of nuclear weapons creates very strong electromagnetic fields that can instantly destroy electronic equipment hundreds of miles away. Radar was also found to cause localized disturbances. It was necessary to develop theories on how electromagnetic fields propagated from these devices and how they caused equipment malfunctions.
In the early 1970’s it was recognized that the same theories developed in World War II could be applied to the problems of localized disturbances affecting computers and televisions. The broadcasting industry petitioned the FCC to regulate electronic equipment to reduce the levels of interference and provide for clear reception of programming. This was the beginning of large scale regulation of all electronic emitters with frequencies greater than 110 Khz.
Testing for EMI
There are two ways in which a specialized EMI testing laboratory can help. First, testing your device for EMI emissions before it goes into production allows you to make the design modifications necessary to meet all applicable standards. Agencies typically require regulation to acceptable levels of noise in the broadband and narrowband categories. Midwest EMI handles everything for you, including interpretation of what is acceptable, how to correct deficiencies, and how to submit data properly to the regulating agency.
Second, testing your device for susceptibility to EMI radiated from other sources helps you increase your device’s reliability by adding protective measures if necessary. The science of fortifying electrical equipment against the effects of EMI interference is called susceptibility engineering. The staff at Midwest EMI have many years of experience in this field.
Military EMI Testing
The Department of Defense regulates EMI testing of military equipment. Testing in accordance with Military Standard 461C usually requires security clearances and is very intensive. Submission of data is very meticulous and detailed and the government may require a special certification. Our chief testing engineer at Midwest EMI is certified by the National Association of Radio and Telecommunications Engineers, Inc. (NARTE).
Medical EMI Testing
Presently the testing of medical devices is mandatory and is covered by the FDA Standard IEC 60601-1-2. The staff at Midwest EMI have many years of experience with creating the necessary files for 4th edition devices. The standard requires higher levels of immunity than most other precedent ones. In particular for home devices, ESD levels of 15 KV must be tolerated and in Table 9 of the standard RF immunity levels of up to 28 V/M are required to be passed. In some cases, EMI changes will require retesting for safety. Midwest EMI has the required hipot, dielectric withstand and grounding continuity testers to assure conformity.
Preventing EMI and its Effects
A variety of techniques and standard have evolved to analyze EMI disturbances. Specialized antennas, spectrum analyzers and a host of other apparatus can measure simulated or actual EMI effects. Agencies such as the FCC and the European VDE organization routinely regulate commercial equipment. IEEE and ANSI have written numerous protocols.
There are many sources of interference that can cause EMI problems, among them unshielded cables and PC board traces carrying high-frequency clocks. Midwest EMI detects and helps you eliminate any EMI problems from your equipment design. We can also help you write meaningful protocols for your future requirements.
It has been found that electrostatic discharge (ESD) is a major source of factory and field failures. Preventive engineering using the appropriate shielding has found to significantly reduce field complaints. European requirements (EN 61000-4-2) require ESD testing. It is particularly important to perform this test on medical equipment as it is related to fail-safe design. Midwest EMI has the apparatus to perform ESD testing to EN 61000-4-2 standards.