Recently, MET Labs performed High Altitude (or Nuclear) Electromagnetic Pulse (HEMP or NEMP) susceptibility testing of U.S. Navy vendor electronics at an outdoor test area in Maryland.
The test method used was RS105 from MIL-STD-461. RS105 addresses the risk of radiated exposure to an EMP event. (CS116 is the MIL-STD-461 test method that addresses conducted – rather than radiated – immunity for EMP).
While EMP susceptibility is increasingly being measured in a number of industries and applications, including data centers, it has traditionally been used for electrical/electronic equipment installed in military environments. Much of this equipment is protected by hardened shielded enclosures, but that which is exposed must have its own built-in shielding effectiveness.
The test setup looks, from the side, like an elongated tent structure, with a surge generator and resistive load on either end on the ground. Rows of wires run between them, up and over a tall support structure in the middle. The wires are evenly distributed, and create a pulsed 50,000 V/m field that radiates down onto the equipment under test (EUT) and a conductive ground plane. This mimics the high amplitude, short duration broadband electromagnetic pulse of a nuclear or similar event.
The RS105 test procedure is:
- Start at 10% of specified level
- Verify waveform
- Apply pulse 5 times (not more than one per minute)
- Rotate EUT 90 degrees, and pulse 5 more times
- Rotate another 90 degrees and pulse 5 more times
- Monitor for signs of degradation
An outside test area, as was used in Baltimore, is preferred due to the relative lack of reflective material. And a large EUT will often necessitate a large test area, as the septum must be three times as high as the EUT.
This testing was conducted to the specifications of MIL-STD-461E, but note that MIL-STD-461G was recently released in draft form. Contact us to learn how the changes in this new standard affect new product development.
Need to know the EMP susceptibility of your commercial or military electronics? Contact us today for a free quotation.
