MIL-STD-461G RS105: Radiated Susceptibility, Transient Electromagnetic Field, or EMP (Electromagnetic Pulse)

MIL-STD-461G RS105 is a requirement applicable to equipment and subsystem enclosures located external to a shielded platform or facility. Therefore this test is intended solely for equipment being used on non-metallic platforms. MIL-STD-461G RS105 applies to Army aircraft for safety-critical equipment and subsystems located in an external installation.

The EUT shall not exhibit any malfunction, degradation of performance, or deviation from specified indications, beyond the tolerances indicated in the individual equipment or subsystem specification when subjected to an EMP waveform. At least five pulses shall be applied at the rate of not more than one pulse per minute.

There are a few variations of EMP to which MIL-STD-461G RS105 tests. Nuclear electromagnetic pulses (NEMP) are magnetic fields caused by nuclear explosions. A high altitude nuclear EMP (HEMP) is another specific test to be performed at higher amplitudes for applications such as aircraft subsystem and component development. Another form of EMP is a non-nuclear electromagnetic pulse (NNEMP), which includes EMPs that are manmade with the use of technology.
 

Test Equipment

The test equipment shall be as follows:

• Transverse electromagnetic (TEM) cell, parallel plate transmission line or equivalent
• Transient pulse generator, monopulse output, plus and minus polarity
• Storage oscilloscope, 700 MHz, single-shot bandwidth (minimum), variable sampling rate up to 1 Giga sample per second (GSa/s)
• Terminal protection devices e. High-voltage probe, 1 GHz bandwidth (minimum)
• B-dot sensor probe
• D-dot sensor probe
• LISNs
• Integrator, time constant ten times the overall pulse width

 

Procedures

The test procedures shall be as follows:

• a. Turn on the measurement equipment and allow sufficient time for stabilization.
• b. Calibration. Perform the following procedures using the calibration setup:
  • (1) Generate a pulse and adjust the pulse generator to produce a pulsed field, as measured with the B-dot or D-dot probes, which meets the peak amplitude, rise time, and pulse width requirements. CAUTION: High voltages are used which are potentially lethal. Record the drive pulse waveform as displayed on the oscilloscope.
  • (2) Tolerances and characteristics of the RS105 limit shall be as follows:
    • (a) Rise time (between 10% and 90% points) between 1.8 ns and 2.8 ns (electric field continuously increasing).
    • (b) Full width half maximum (FWHM) pulse width equal to 23 ns ± 5 ns.
    • (c) The peak value of the electric or magnetic field for each grid position: 0 dB ≤ magnitude ≤ 6 dB above the limit.
  • (3) Repeat steps 5.22.3.4b(1) and 5.22.3.4b(2) for the other four test points on Figure RS105-2.
  • (4) Determine the pulse generator settings and associated pulse drive amplitude which simultaneously satisfies the field requirements for all five grid positions.
• c. EUT testing. Perform the following procedures using the test setup:
  • (1) Turn on the EUT and allow sufficient time for stabilization.
  • (2) Test the EUT in its orthogonal orientations whenever possible.
  • (3) Apply the pulse starting at 10% of the pulse peak amplitude determined in 5.22.3.4b(4) with the specified waveshape where practical. Increase the pulse amplitude in step sizes of 2 or 3 until the required level is reached.
  • (4) Ensure that the drive pulse waveform characteristics at the required test level are consistent with those noted in 5.22.3.4b(2).
  • (5) Apply the required number of pulses at a rate of not more than 1 pulse per minute.
  • (6) Monitor the EUT during and after each pulse for signs of susceptibility or degradation of performance.
  • (7) If an EUT malfunction occurs at a level less than the specified peak level, terminate the test and record the level.
  • (8) If susceptibility is noted, determine the threshold level in accordance with 4.3.10.4.3.

 

Test Setup

Set up the EUT as described below. CAUTION: Exercise extreme care if an open radiator is used for this test.

• a. Calibration. Configure the test equipment in accordance with Figure RS105-2.
  • (1) Before installing the EUT in the test volume, place the B-dot or D-dot sensor probe in the center position of the five-point grid in the vertical plane where the front face of the EUT will be located (see Figure RS105-2).
  • (2) Place the high-voltage probe across the input to the radiation system at the output of the transient pulse generator. Connect the probe to a storage oscilloscope.
• b. EUT testing. Configure the test equipment as shown in Figure RS105-3 for testing of the EUT.
  • (1) Place the EUT centerline on the centerline of the working volume of the radiation system in such a manner that it does not exceed the usable volume of the radiation system (h/3, B/2, A/2)/(x,y,z) as shown on Figure RS105-3 (h is the maximum vertical separation of the plates). If the EUT is mounted on a ground plane in the actual installation, the EUT shall be placed on the radiating system ground plane. The EUT shall be bonded to the ground plane in a manner that duplicates the actual installation. Otherwise, the EUT shall be supported by dielectric material that produces a minimum distortion of the EM fields.
  • (2) The EUT orientation shall be such that the maximum coupling of electric and or magnetic fields is simulated. This may require more than one test orientation.
  • (3) Cables for EUT operation and monitoring shall be oriented to minimize induced currents and voltages on the cables. Cabling shall be oriented normal to the electric field vector and in a manner that minimizes the loop area normal to the magnetic field vector. Cables extending out of the parallel plate working volume should remain normal to the electric field vector for a minimum distance equal to 2 times h.
  • (4) Bond the bottom plate of the radiation system to an earth reference.
  • (5) Keep the top plate of the radiation system at least 2 times h from the closest metallic ground, including ceiling, building structural beams, metallic air ducts, shielded room walls, and so forth.
  • (6) Place the EUT actual or simulated loads and signals for electrical interfaces in a shielded enclosure when an open radiator is used.
  • (7) Place transient protection devices (TPDs) in the EUT power lines near the power source to protect the power source.
  • (8) Connect the transient pulse generator to the radiation system.

Waveform Specifications




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