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For the Department of Defense, specifying a computer’s electromagnetic interference (EMI) and its electromagnetic compatibility (EMC) is a vital indicator on how well the computer will operate within many “noisy” environments.

This is such an important factor that there’s a military standard dedicated just to this EMI/EMC issue.

MIL-STD-461 breaks down the EMI requirements for a wide range of applications, from trucks and ships to aircraft and fixed installations, as well as the various requirements within an application (e.g., above deck versus below deck on a Navy ship).

MIL-STD-461 provides the requirements for the control of electromagnetic interference (EMI) emissions and susceptibility characteristics of electronic, electrical, and electromechanical equipment and subsystems designed or procured for use by activities and agencies of the Department of Defense.

This standard is best suited for bench top mounted or free standing equipment, with a power input current draw of less than 200 amps. It is not commonly applied to items such as components and independent modules located inside electronic enclosures, nor entire platforms such as an aircraft or submarines.

Of particular concern to the DoD is when EMI is intentionally used in electronic warfare for radio jamming.

EMC can be grouped into two categories:

  • Immunity testing – measures how a device will react when exposed to electromagnetic noise and other disturbances. The purpose of these tests is to gain a reasonable assurance that the device will operate as intended when used within its expected operating environment.
  • Emissions testing – measures the amount of electromagnetic noise generated by a device during normal operation. The purpose of these tests is to ensure that any emission from the device are below the relevant limits defined for that type of device. This, in turn, provides a reasonable assurance that the device will not cause harmful interference to other devices operating within its expected operating environment.

Regulatory compliance and due diligence require that electronic devices undergo one or both types of testing.

Want to learn more? Tonex offers Military EMI/EMC Training, a 3-day comprehensive course that covers the theory of EMC/EMI and all aspects of MIL-STD-461 and MIl-STD-464. Training also covers the basic math and the physics of EMI/EMC and the fundamentals of instrumentation, instruments, test setups and real measurements.

For more information, questions, comments, contact us.

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