Electromagnetic Compatibility (EMC) is a term used to describe how a device performs in an environment of electromagnetic noise. EMC includes two factors — a device's tolerance to emissions (noise immunity) and how much emission it produces. The goal is to limit the unintentional generation, propagation and reception of electromagnetic energy. EMC is characterised by several aspects.
EMI refers to the phenomenon of electromagnetic radiation, when the emission interferes with electronic components and RF systems. We commonly use dB as a unit of EMI noise measurement.
EMC is a term that describes how well a device blocks or withstands EMI. The ability of an equipment to operate in an environment where EMI is present is a measure of its EM Compatibility.
EMI is not a directly visible phenomenon and is highly dependent on the installation site and surrounding equipment. So manufacturers cannot easily gauge if their products are electromagnetically compatible. The only real way to find out is to conduct scientific EMC Tests. They are performed with a production model, and often repeated post-production, onsite to ensure compliance is maintained following changes in the production. OEM parts and accessories should come with a Declaration of Conformity and be checked for compatibility with the final product's intended use.
EMC Testing is the only way to prevent ill-effects of electromagnetic noise, such as equipment damage, energy wastage or increase in maintenance costs. Several well published industrial products have been recalled or withdrawn from the market because electromagnetic compatibility and EMC Testing was not fully considered. Failing to meet EMC and RF regulations can deny equipment manufactures entry into export markets which have stringent EMI/EMC compliance standards.
Electromagnetic Compliance Testing can be categorised into several types depending on the particular stage of the product life cycle in which it is performed.
Development EMC test - When the electronic circuit design is still in progress, it is easy to make alterations to the design. So informal EMC testing is carried out to roughly estimate the EMI levels of the various components. The circuit design and EMC filters can be quickly adjusted accordingly.
Pre-compliance EMC test - When a representative prototype of the product is ready, preliminary compliance testing of the product is performed in the controlled lab environment.
EMC Compliance Test - A series of mandatory EMC compliance tests are conducted depending on the nature of the product and the market it is intended for. Defence and medical applications may have their own specific tests. Export oriented compliance such as CE marking also requires a specific set of compliances. The EMC compliance test categories are further divided as follows:
EMI/EMC tests are conducted in specialized and accredited test facilities. These tests involve test methods, equipment and measurement sites in compliance with national or international standards. Outcome of testing is to certify that a device meets the required standards. Compliance with national or international standards is defined by individual nations. Compliance tests are commonly done prior to production of a device.
Testing is typically divided into two categories: Emissions testing and Immunity testing .
Emissions testing : Measures RF emissions, both radiated and conducted, of a device or Equipment Under Test (EUT). Certifies that emissions levels do not exceed the limits defined by the appropriate standard.
Immunity testing : RF energy is transmitted onto a device or Equipment Under Test (EUT) to verify if the EUT operates correctly and without fault while under such an environment, according to the appropriate standard.
Open-air test sites (OATS) are the reference sites used for most standards. They are especially used for emissions testing of large equipment systems. However, RF testing of a physical prototype is more often carried out indoors, in a specialized EMC test lab chamber . Different type of test chambers include anechoic, reverberation and the gigahertz transverse electromagnetic cell (GTEM cell).
A number of different EMC standards, each with their own requirements related to test set-up, power levels, frequencies, and many other details, have been developed over time. Different standards have been adopted by different nations, with some standards designed for harsh military requirements, while others are intended for a benign suburban environment.
Governing bodies in the European Union with respect to EMC include the IEC, CISPR, and the European Committee for Electro-technical Standardization (CENELEC). The IEC coordinates international standardization and related matters, while CENELEC and CISPR are largely responsible for approving detailed EMC standards to demonstrate compliance with the EMC Directive. Products sold in the European Union must be in compliance with EMC Directive, 89/392/EEC. Products that meet the EMC directive carry the "CE" mark that signifies the manufacturer's assertion of compliance.
MIL-STD (latest being MIL-STD-461F issued in December 2008) defined by the Department of Defence, USA is a system-level standard that specifies EMC requirements and limits. It consists of EMC requirements, EMC test set-up and methodology and EMC definitions and acronyms.
It is based on the operational platform for deployment (surface, ships, aircraft, etc.) and location on that platform (internal or external). The overall requirement is comprised of eighteen sub-tests that cover diverse system characteristics ranging from emissions conducted via power leads to spurious and harmonic radiated emissions.
This testing is not inexpensive and is quite elaborate. The five core tests (RS103, RE102, CS101, CS114 and CS116) will require roughly two days of lab time; the entire standard, seven to ten days.
The right choice for the EMI filter depends on several factors governing the product to be protected and the installed environment.
Type of compliance - Immunity or emission test compliance, safeguard against transient noise are some of the compliance types.
EMISINDIA is a trusted name when it comes to EMC testing and consultancy services . Our expert engineering and consulting team provide support to design, plan, execute, inspect and verify EMC compliance systems. EMIS can help customers with their products to meet International EMI/EMC standard compliance by providing suitable solutions within a short time span.
Our test facility is accredited by the National Accreditation Board for Testing and Calibration Laboratories (NABL) in accordance with the standard ISO/IEC 17025:2017. We also support on-site testing in compliance with international standards. EMIS also has a DSIR (Department of Scientific and Industrial Research, Government of India) recognised R&D Lab where customers can avail a wide range of military compliance safety testing services.
Customers can avail of the following testing services offered by EMIS: