MIL-STD-461G Testing

MIL-STD-461G Testing

(Did You know?)

MIL-STD-461: Electromagnetic Interference / Electromagnetic Compatibility (EMI/EMC)

Washington Laboratories has extensive experience in MIL-STD-461G Compliance Testing.

We can help. Getting approvals for your products can be frustrating, but it doesn’t have to be.  We specialize in testing and engineering for product compliance.

Military and Aerospace Systems must comply with Electromagnetic Compatibility (EMC) requirements. MIL-STD-461 is applied to Department of Defense (DoD) procurements for equipment and subsystems.

MIL-STD-461G Testing encompasses a wide variety of test methods for Military and Aerospace Systems such as; Surface Ships, Submarines, Army Aircraft (Flt Line), Navy Aircraft, Air Force Aircraft, Space Systems (Launch), Army Ground, Navy Ground, and Air Force Ground.

We provide testing and design support for the following:

  • CE101:  AF Currents, Power Leads
  • CE102:  RF Potentials, Power Leads
  • CE106:  Antenna Port
  • CS101:  Power Leads
  • CS103:  Antenna Port, Intermodulation
  • CS104:  Antenna Port, Rejection of Undesired Signals
  • CS105:  Antenna Port, Cross-modulation
  • CS109:  Structure Current
  • CS114:  Bulk Cable Injection (RF)
  • CS115:  Bulk Cable Injection (Impulse)
  • CS116:  Damped Sinusoidal Transients
  • CS117:  Lightning Induced Transients
  • CS118:  Personnel Borne ESD
  • RE101:  Magnetic Field
  • RE102:  Electric Field
  • RE103:  Antenna Spurious & Harmonic Outputs
  • RS101:  Magnetic Field
  • RS103:  Electric Field
  • RS105:  Transient Electromagnetic Field

MIL-STD-461 Testing Methods Chart

Each test method may include various test limits or susceptibility test levels. Contact us for assistance!

MIL-STD-461G Testing

MIL461G Applicability – view PDF

Learn more about our MIL-STD Testing Services

Did You Know? MIL-STD-461G

Did you know that MIL-STD-461G (4.3.11) deleted the requirement for periodic calibration of passive antenna, current probe and LISN calibration unless repaired?

Concern: The premise for deletion of this calibration is that the system integrity check in the procedures would determine acceptability. However, the procedure integrity check removes the antenna so it is not checked with a known signal level. The procedure also calls for detection of a signal from a stub radiator without knowing the field strength of the signal. Antenna with a balun or connected elements that could be loose or corroded would go unchecked. If adopting the no calibration approach, you should generate a known signal level and fix radiator and receive antenna at a specific location to obtain a repeatable check and track the periodic integrity checks for trends to identify changes that could affect your measurements.

Article Reference ID: DYK00001

Did you know that MIL-STD-461G brought about the need for reducing facility power losses for the CS101 interfering signal?

Discussion: In MIL-STD-461G, A.5.7 if the specification limit cannot be developed and the pre-calibrated power limit is reached, it is “incumbent” that the tester check that the missing signal is not being dropped across the power source.  As shown in the sketch, a facility power filter often includes a series inductance that is not adequately bypassed by the bypass capacitor in the test circuit configuration at frequencies below 10 kHz.  Instructions indicate that the facility power filter may need to be removed to compensate and for DC power the bypass capacitor value increased to provide for the test voltage at the test article power input. Good idea – of course!

However the appendix (where this appears) is provided for guidance and is “not a mandatory” part of the standard.  If you would like more detail, don’t hesitate to contact us.

facility power filter

Article Reference ID: DYK00002

Did you know that MIL-STD-461G calls for verification of the EUT bonding prior to test before connecting cables (4.3.8.2)?

Discussion:  Over the years the test article configuration has been made to conform to the 2.5 milli-ohm standard for bonding the ground plane to the enclosure wall.  This basically violated the rule to configure as installed.  We have seen approval representatives go to extreme measures to attain a 2.5 milli-ohm impedance connection from an equipment connector to the ground plane with several bond connections in the measurement path.  If the equipment chassis to ground connection is provided by the protective ground connection only, then the measurement should be an open circuit until that cable is installed.  We should NOT allow the measurement to mis-lead us into making an artificial ground connection.  The goal is to make the intentional ground connection and measure without adding other parallel paths (cable shields, etc.).  If you record a measurement without the intended connection, then you may be encountering incidental connections that are not assured in the installation.  Remember that 2.5-milli-ohms is not an equipment grounding requirement unless the installation specifies.

Article Reference ID: DYK00003

 

Did you know that the new configurations using >28,000uF capacitors may need a pre-charge to prevent in-rush current from tripping the power source?

CS101 and CS117 configurations call for installation of a >28,000uF capacitor for DC powered devices.  At power on, the uncharged capacitor tends to act as a short circuit producing a significant in-rush current that may cause the power source to trip.  To help with this situation, a pre-charge circuit that controls the in-rush may be inserted to support charging the capacitor and then switching out when the charge is accumulated.  The drawing below shows a very basic pre-charge configuration – remember to use properly rated components if you decide to construct your own.

>28,000uF capacitors

For more information contact us.

Article Reference ID: DYK00011

Did you know that you can filter the power frequency to provide improved measurement resolution during CS101 testing?

The ability to measure the low level signals in the presence of the power frequency at high levels especially at the lower test frequencies is difficult.  The circuit below is a power filter that works with a 10X scope probe and 1MΩ oscilloscope input; it is designed to attenuate the power line frequency.  This circuit will need to be calibrated or characterized to determine the insertion loss across the frequency range of the test.  Note that using other than a 10X probe and 1MΩ input will yield different performance – calibrate your filter and observe component ratings – caution, high voltage circuit.

CS101 testing

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Article Reference ID: DYK00012

Did you know that MIL-STD-461 revision “G” defines a cable bundle as all wires and shields associated with a specific connector?

Discussion: This makes sense but it can lead us into making a poor choice in accomplishing selected tests.  For example if a connector wiring harness goes in two different directions as it exits the equipment the wiring will not be equally exposed to RF fields.  If we test the cable bundle for conducted susceptibility as a common field, then we would not induce differential signals missing a potential issue.  The good part is that tailoring allowed by the standard permits us to compensate for this risk and test each of the split bundles separately.   Note that the MIL-STD-461 configuration is based on a generic layout to cover many types of installations, but if we have specific installation parameters, we need to consider tailoring to emulate an actual installation.  This helps prevent a false pass or false fail leading to field issues or costs to solve a non-existent problem.

For more information contact us.

Article Reference ID: DYK00013

Did you know that determining the emission mode (common or differential) is easily accomplished during CE101 testing?

CE101 calls for using a current probe to measure low frequency RF emissions with testing on both the phase and neutral (positive and negative) power leads.  If emissions are measured at a level that indicates resolution is needed, the designer may need to have insight on the emission mode.  Because the measurements are accomplished on each line separately, the mode is not obvious.  However a quick check with both power leads in the current probe will provide a good indication on the mode.

If the measurements with both leads show a significant reduction, then differential (normal mode) emissions are present.  Since normal current enters on one line and returns on the other with a 180-degree phase shift the current will cancel, showing the reduction.  If the emission measurements do not change with both leads together, then common mode emissions are indicated.

CE101

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Article Reference ID: DYK00015

Did you know that MIL-STD-461G added a process of verifying the bonding to ground plane for the test configuration?

MIL-STD-461G has added a process of verifying the bonding to ground plane for the test configuration. Bonding of the ground plane to the shielded enclosure and bonding of the LISN to the ground plane with a resistance of

This video tutorial discusses this subject and guides the test personnel in configuring the test item to obtain these measurements – note that 2.5milliohms is NOT the required resistance for this configuration.

MIL-STD-461G Bonding Measurements Video

For more information contact us.

Article Reference ID: DYK00017

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