This means the test cable must be fed through a coupler which is driven by the MIL test generator. One coupler that can be calibrated for all waveforms and then left in place on the EUT test cable, reduces test time and the possibility for operator error considerably. CN-BT6 gives users this increased security together with a larger cable aperture of 6cm diameter. The system can be calibrated for all waveforms, setup data is stored in MIL memory for easy recall. Once the system is calibrated, the coupler CN-BT6 can be left in place on the test bench and tests performed without having to breakdown and reset the equipment under test. This represents a great saving in time and reduces the possibility of an operator error.
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The standard has evolved since the initial issue was released more than 50 years ago, with many changes to the specific requirements and tests. Technology advances and issues with compatibility have spurred updates to the standard. The system requirements may impose tailored MIL-STD requirements for the subsystem qualification to support a specific application.
This indicates that MIL-STD requirements support generic usage for equipment that serve most cases, and tailoring applies to unique cases. Even as a generic type of standard, many variances to support wide-spread applications are included.
The evolvement of MIL-STD includes some significant milestones that the product developers have faced and how changes have affected their approach to designing control measures. Documentation has always been a key element of EMC test and evaluation programs.
However, tailoring may be preferred where the test configuration conforms to the actual installation if the device is used for a specific purpose. Documentation of the test configuration should support being able to re-create the initial test. The standard includes 19 test and evaluation methods that document the various test parameters, plus general requirements to document many of the test parameters. In the early days, the focus was interference with radio communications that evolved into communications system.
The goal was to evaluate products and build EMC into the design process, instead of dealing with the issue when interference was observed after deployment.
MIL-STD was updated through a series of notices , which expanded the scope of the testing with methods to support the evolving changes of MIL-STD and to correct errors identified over the years. A few of the changes that had a major impact were: Manually actuated switching transients occurring at the moment of actuation are exempt from MIL-STD requirements.
Although the manual transient was removed from MIL-STD, the applicable power quality standard still contained testing for these events. Also, the system specification could include the requirement to control these transient emissions. Narrowband and Broadband emission categorization was deleted and test receiver bandwidth to be used for various frequency range was defined. This move brought more realization that EMC was more than dealing with radio noise, with equipment upset recognized as a major EMC need.
Shielded enclosure test facilities were required to include RF absorbers to reduce reflected energy, improving the repeatability of the test measurements. The RF absorber layout was provided in figures and the performance requirements for absorption were specified. The test configuration requirements were defined in more detail, as was a requirement to use cables that conformed to the installation drawings. This effectively closed a loophole wherein many equipment qualification tests ignored the contribution of cables to the emission and susceptibility of the device.
Some equipment manufacturers tended to avoid cables when qualifying equipment, so this change removed the ability to use unreasonable measures to avoid the cable contribution to compliance. A few minor updates were part of the revision changes. MIL-STDF was released in as part of the normal review cycle for standards with a few changes notably: CS was added to the requirements table with applicability to ships.
CS testing with the test article powered off was deleted based on data collected demonstrating that issues identified with power off showed like issues during power on testing. The use of shielded power cables was not permitted.
This included a mandate to extract the power leads from cable bundle including shielded bundles if power was part of the interconnecting bundle. The appendix provided some exceptions when the power was isolated from the mains. Measurements of the test article bonding to the ground was added as information to be included in the test report. Proper grounding has been an integral part of EMC control and many test configurations installed low impedance ground connections without regard to the installation.
The standard does not establish a specific value but calls for checking that the grounding conforms to the installation. CS was deleted although it had been placed into the requirements by the previous revision.
CS testing was added to the requirements to evaluate lightning-induced transients for selected applications where the platform may not provide adequate protection for such events. This addition brings the system level requirement to the equipment level. ESD evaluations were previously a separate issue that was managed under various static control programs that were limited in establishing a test requirement. Periodic calibration of passive test equipment items was required only if the item was repaired.
This helped mitigate some of lab operation costs, but the signal verification checks associated with the various tests were expanded for a more thorough check. One should realize that the checks are a necessary function to prevent errors, and the associated cost of upgrading or over-design to compensate for the error.
This aided in reducing test time and made capture of the transient spectral content measurements a relatively simple process.
Over the years many changes have been made, with the list above just mentioning a few. The more recent revisions have included appendices that work toward rationalizing the test objectives and documenting how the program has evolved. Data Item Descriptions DIDs provide guidance for preparation of documents associated with procurement specifications.
This document is prepared early in the product development process to provide a design guide to incorporate EMC control measures. If associated with a development procurement, the EMICP is required within days of contract award. This gives the agency an opportunity to confirm that the contractor understands the EMC requirements and has a feasible approach to meeting those requirements.
The content includes: Management — Document responsibilities for design, test and overall program oversight with names and contact information for key personnel. List sub-contractors and how the EMC requirements are imposed on the sub-contractor. Of course, the device needs to be fully described including the installation. Discuss the plans for identifying and mitigating potential problems. This is also an opportunity to identify conflicting requirements and seek resolution via a contractual review — if contract has resolved conflicts then be sure to document the final agreement.
Design techniques and procedures — Describe how to incorporate control measures to address: 1 spectrum management, if applicable; 2 mechanical design shielding, compartments, openings, bonding, corrosion control, etc.
Analysis — provide a thorough analysis on how the design techniques will yield control for each of the identified requirements. If filtering is to be used as a control measure, discuss how a filter insert with selective capacitance can reduce emissions and limit susceptibility without degrading the signal integrity.
Developmental testing — describe how models will be used to assess the EMC performance through testing and how the test results will be used to make changes in the design. This document provides the details for testing and the instructions for the test technical staff. Content includes: Introduction contains a complete listing of the tests to be performed along with a detailed product description that includes operation, installation data, and power usage.
List approved deviations to contract requirements. Applicable documents — list military, government, industry, and company standards that support the testing program. Test site — describe the facility shielded enclosure or open area site , the grounding scheme and precautions listed in MIL-STD Test instrumentation — describe what test equipment is planned for use and its characteristics e. Describe operations by software and the verification process to assure software is functioning properly.
Provide a listing of the scan rates and dwell times and confirm that the cycle time of the test item is within the dwell period. Document how the interfaces electrical and mechanical are used to support the functionality and monitoring of test article performance.
EUT operation — describe how the test article is operated during testing and the rationale for selecting the operational modes. Define the acceptance criteria objectively, with clear guidance on what performance element constitutes non-compliance. Measurements — provide step-by-step instructions for performing each of the tests with the applicable instrumentation for the individual tests.
List the information to be recorded during the test and provide samples of the data sheets, logs and graphs. Understanding the EMITR content requirements is necessary to assure that all pertinent information is collected during the testing. Administrative data — this area should provide the overview of the results along with the administrative details related to the contract.
Describing the actual test article is specified with detailed information on the build status e. Information should be adequately detailed to support re-creating the test if necessary. The details are frequently associated with individual tests, so locating with the detailed results section may be appropriate.
Detailed results — calls for documenting a lot of information about the EUT design, test setup, test instrumentation, measurements and data reduction calculations. If the EUT is found to be susceptible, threshold measurements are to be part of the report. Conclusions and recommendations should be included, and if non-compliance issues are identified the conclusions should include actions to be taken to assure compliance.
How is the test configuration managed? MIL-STDG provides a lot of detail in the general and interface requirements section on establishing and managing the test configuration. Configuration management is critical in the standardization process where each test laboratory should obtain the same results within the margin of uncertainty. We must realize that the configuration will not follow exactly in many cases where specific parameters prevent configuration conformance.
This inability to follow the prescribed layout reminds us to look at ways to get reasonably close and to document the layout thoroughly to support repeating the testing. If a known installation applies to a device in all cases, then duplicating the installation as the test configuration would be preferred.
Figure 1. Floor Standing Configuration Figure 1 shows a floor-standing test configuration modeled after the drawing in MIL-STD to point out a few items that are misread in the standard. This illustration shows that a table-top arrangement for the cable layout has been brought into the standard elevating the cables cm above the enclosure floor.
The cable elevation increases the loop area formed by the cable to the ground plane even with the table-top maintaining the 5 cm elevation. The cable routing between the EUT and table-top opens the area providing a significant risk of increased radiated emission levels and reception of interference. A quick solution could be to add a filter insert without having to re-design the device to control EMI from the circuitry.
As always, the cable arrangement influences the test results, so pay attention to the cable routing and document the arrangement in detail to allow re-creating the test. The conducted tests are affected by the layout because of parasitic components and mutual reactance formed by placement. Using the RF absorber requires that the table-top ground plane use long straps to attach it to the enclosure, usually going through the absorber at the floor junction.
The length-to-width ratio should be at least to reduce the inductive reactance of the bond. Note that a EUT bonding connection is located near the lower right corner. This should only be present if used in the installation. Are bonding and grounding requirements specified? The bonding is required to use the design provisions for connecting the equipment case to mounts or to the ground plane and to use methods as specified in the installation drawings.
This addition effectively removed the tendency to make special ground connections and bonds of 2. Note that a value is not specified but conformance to the installation is required.
Verification of the bonding should be accomplished prior to test and corrections made if found to be deficient before testing proceeds.
MIL-STD-461 – Revisions A – D
However, little is known about early efforts to address RFI problems until the early s. That document "protected" radio receivers from interference by requiring shielding of the vehicle ignition system, regulator and generator. The requirement was simply that the vehicle operation not "disturb" radio reception. With the increased use of mobile radio communications, it became apparent SCL was inadequate. In it was superseded by specification , "Vehicular Radio Noise Suppression" that addressed in addition to shielding the use of filters, by-pass capacitors, resistor-suppressors, bonding, grounding and proper wire routing. This specification also defined an instrumentation system and a limit.
Solar 10 µF Feed-Thru Capacitors in RFI/EMI for MIL-STD-461A/462A
The standard has evolved since the initial issue was released more than 50 years ago, with many changes to the specific requirements and tests. Technology advances and issues with compatibility have spurred updates to the standard. The system requirements may impose tailored MIL-STD requirements for the subsystem qualification to support a specific application. This indicates that MIL-STD requirements support generic usage for equipment that serve most cases, and tailoring applies to unique cases. Even as a generic type of standard, many variances to support wide-spread applications are included. The evolvement of MIL-STD includes some significant milestones that the product developers have faced and how changes have affected their approach to designing control measures.
Content uploaded by Sandeep Satav Author content All content in this area was uploaded by Sandeep Satav on Sep 13, Content may be subject to copyright. These are major differences between C and E versions and EMI test labs took several years to upgrade as per E version. A study report is presented in the form of paper in which a review of the changes has been presented along with brief history of the DoD standards for EMI and EMC. EMI testing as per a prescribed standard is recommended. EMI test standards are scientifically written documents, which defines prescribed maximum acceptable electromagnetic emission as well as tolerable electromagnetic susceptibility levels for various categories of systems and sub-systems.