MIL-STD-188-125-1: High-Altitude Electromagnetic Pulse (HEMP) Testing

MIL STD 188-125-1

MIL-STD-188-125-1 is a military standard for the testing of electromagnetic shielding effectiveness. This standard was developed by the United States Department of Defense and outlines the procedures for evaluating the ability of a material or system to block electromagnetic energy. The standard is widely used in military and aerospace applications, as well as in commercial and industrial settings, to ensure that components and systems are protected against electromagnetic interference (EMI).

The testing specified in MIL-STD-188-125-1 is designed to simulate real-world conditions, and involves exposing components and systems to electromagnetic energy in the frequency range of 30 MHz to 1 GHz. The testing procedure measures the level of interference that the component or system experiences as a result of the exposure, and determines its ability to operate as intended in the presence of electromagnetic energy.

Summary of MIL-STD 188-125 HEMP Compliance Testing

The MIL-STD-188-125-1 test standard defines the design and testing criteria. Specifically designated for fixed ground-based facilities in HEMP-hardened, critical, time-urgent C4I networks. Facilities include subscriber terminals and data processing centers, transmitting and receiving communications stations, and relay facilities. MIL-STD-188-125-1 applies to both new construction and the retrofit of existing facilities.

Local portions of facility interconnects are addressed. However, it is assumed that survivable long-haul communications paths, fiber optic links, or other hardened interconnects between facilities may be required to pass. MIL-STD-188-125-1 can also be used for HEMP protection of other ground-based communications-electronics facilities that require HEMP hardening.

MIL-STD-188-125-1 testing must ensure that the test setup accurately represents real-world conditions. This includes proper placement of the component or system under test, as well as the use of appropriate test equipment, such as an anechoic chamber or a shielded room. Additionally, the testing procedure must be performed in accordance with the requirements outlined in the standard, including the use of specified test frequencies, test methods, and measurement procedures.

The results of MIL-STD-188-125-1 testing provide important information on the electromagnetic compatibility of the component or system under test. This information can be used to evaluate the susceptibility of the component or system to electromagnetic interference, identify areas for improvement, and determine if the component or system meets the desired electromagnetic compatibility requirements.

Scope of the Military Standard Test Method 188-125-1

To gain a better understanding of the requirements, it is important to understand the specific terminology used in HEMP testing.

Electromagnetic stress

A voltage, current, charge, or electromagnetic field that acts on a piece of equipment.  If the electromagnetic stress exceeds the vulnerability threshold of the equipment, mission-aborting damage or upset may occur.

Facility HEMP shield

The continuous conductive housing that substantially reduces the coupling of HEMP electric and magnetic fields into the protected volume.  The facility HEMP shield is part of the electromagnetic barrier.

HEMP Hardness Surveillance/Re-Verification Testing

Testing conducted at prescribed intervals during the operational phase of the facility life cycle. This testing is for evaluating whether the HEMP protection measures continue to provide the required HEMP hardness. HS/re-verification test requirements are established in the technical manual.

Main Barrier Electrical POE Protective Device

A protective device installed on an electrical conductor that penetrates from the system exterior, through the HEMP shield, and into the protected volume.  Main barrier protective devices must meet the performance requirements of this standard.

Special Protective Volume

A HEMP-protected space within the facility, where electromagnetic stresses due to HEMP may exceed the residual internal stress limits for the protected volume.  The special protective barrier may be a separate shield with protected penetrations. These are more commonly, shielded cables or conduits, and equipment cabinets and closed piping systems are used to provide the needed electromagnetic isolation from the protected volume.

Vulnerability Threshold

The minimum stress level that causes the equipment to suffer definite damage or performance degradation.  In the context of this standard, the vulnerability threshold is the minimum electromagnetic stress that causes mission-aborting damage or upset.

Expert HEMP Military STD-188-125-1 Compliance Testing

Keystone Compliance has completed numerous site surveys to determine the level of protection against HEMP attacks. Our team diligently completes the assessments and provides valuable feedback on any weaknesses that should be addressed. This feedback often includes suggestions for remediating any aperture points of entry (POE) and conductive points of entry.

In addition to shielding effectiveness testing, Keystone Compliance provides a full suite of regulatory compliance testing needs under one roof; this includes IP code, climatics, dynamics, and package integrity testing. Lastly, our experience provides insight on improving protection as well as in determining specific locations within the facility that be more likely to serve as a point of entry. 

Please Contact Us or Request a Quote for MIL-STD-188-125-1 testing to determine the HEMP-readiness of your facility.

Diagram of HEMP Military STD-188-125-1MIL-STD-188-125-1 Shielding Effectiveness Certification Testing

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