MIL-STD-461 – Revisions A - E

Much of the testing specified in the standards listed in the tables below is derived from the A, B and C versions of MIL-STD-461.  While there is a fair amount of redundancy, recognizing the subtle differences between the different versions of 461 and its derivative standards is important as it will impact the cost of the testing as well as the degree of difficulty in complying. Details regarding the current version of the MIL-STD-461 Revision G, as well as Revisions E and F can be found on the main MIL-STD-461 page.

Standard

Tests

Comments

MIL-STD-461A, B, C

MIL-STD-462

CE01, CE02, CE03, CE04, CE06, CE07, CS01, CS02, CS03, CS04, CS05, CS06, RE01, RE02, RE03, RE04, RS01, RS02, RS03

First published in 1967 to provide a joint specification for the Army, Navy and Air Force, MIL-STD-461A is still referenced today.  Updated in 1980 as 461B and again in 1986 as 461C, changes included an expanded scope as well as modifications to the limits originally defined in the A-version.  MIL-STD-462 defines the test methods used and all documents have numerous notices.

MIL-STD-461D

MIL-STD-462D

CE101, CE102, CE106, CS101, CS103, CS104, CS105, CS109, CS114, CS115, CS116, RE101, RE102, RE103, RS101, RS103, RS105

Published in 1993, 461D was a first step towards harmonizing the MIL-STD and commercial test methods.  Significant improvements included defining measurement bandwidths for emission testing and scan rates/step sizes & dwell times for immunity testing.  Test methods are defined in 462D.

MIL-STD-461E

CE101, CE102, CE106, CS101, CS103, CS104, CS105, CS109, CS114, CS115, CS116, RE101, RE102, RE103, RS101, RS103, RS105

While subtle changes were made from the D-version, the most radical change was integrating the limits and test methods into one document.  Similar to 461D, this document was published with an application guide which gives an historical perspective on the reasons for the various tests and helps to clarify the methods used in this testing.

Until the publication of 461E, MIL-STD-461 documented the test limits and levels while MIL-STD-462 specified the test methods & procedures that were to be used for conducting the tests.  The E version of this standard combined both into one document.

Some general pieces of information will be helpful in navigating the military standards.  The military and aerospace world uses the term susceptibility, rather than immunity used in the commercial world.  In addition, recognizing the following abbreviations will be helpful:

·         CE = conducted emissions

·         CS = conducted susceptibility

·         RE = radiated emissions

·         RS = radiated susceptibility

·         NB = narrowband

·         BB = broadband

MIL-STD-461A

This standard provides an interesting read from a historical perspective because it specifies the requirements for some of the antennas that should be used for the testing.  Figures 2B and 2C refer to the "outrigger" elements for what is more commonly known today as the biconical antenna.

Table I of this standard categorizes the different types of equipment that might be tested.  The table below lists most of the tests covered by this standard, and which tests apply to which types of equipment.  (The table below shows the most commonly performed tests of MIL-STD-461A, but is not a comprehensive list of all tests covered by this standard.)

Test

Description

CE01

Conducted emissions, power leads, 30 Hz to 20 kHz

CE02

Conducted emissions, control and signal leads, 30 Hz to 20 kHz

CE03

Conducted emissions, power leads, 20 kHz to 50 MHz

CE04

Conducted emissions, control and signal leads, 20 kHz to 50 MHz

CE06*

Conducted emissions, antenna terminals, 10 kHz to 12.4 GHz

CS01

Conducted susceptibility, power leads, 30 Hz to 50 kHz

CS02

Conducted susceptibility, power leads, 50 kHz to 400 MHz

CS03*

Conducted susceptibility, intermodulation, 30 Hz to 10 GHz

CS04*

Conducted susceptibility, rejection of undesired signals, 30 Hz to 10 GHz

CS05*

Conducted susceptibility, cross modulation, 30 Hz to 10 GHz

CS06

Conducted susceptibility, power leads, transient spike

RE01

Radiated emissions, magnetic field @ 7 cm, 30 Hz to 30 kHz

RE02

Radiated emissions, electric field @ 1 meter, 14 kHz to 10 GHz

RE03*

Radiated emissions, spurious and harmonic emissions, 10 kHz to 40 GHz

RE04

Radiated emissions, magnetic field @ 1 meter, 20 Hz to 50 kHz

RS01

Radiated susceptibility, magnetic field, 30 Hz to 30 kHz

RS02

Radiated susceptibility, magnetic induction fields

RS03

Radiated susceptibility, electric field, 14 kHz to 10 GHz

*limited applicability - applies to antenna ports only.

Although this standard is not often used anymore, it can still be called out when a part that was originally qualified more than 25 years ago is replaced with new hardware.  The rationale behind this is that if it worked for hardware that was previously qualified, it will work for the replacement hardware.

One of the most important aspects of this standard that one should be aware of is the extremely stringent limit for CE01 and CE03, conducted emissions on power leads.  The chart below compares the CE03 narrowband curve for 461A to the most stringent CE03 limit in 461B.  Although both curves specify 20 dBuA (10 uA) of current from 2-50 MHz, the A-version is more stringent at lower frequencies where low-order harmonics of switched mode power supplies (SMPSs) are likely to reside.  This would clearly impact the front-end filter design of a SMPS.

milstd461-a-b-narrowband

MIL-STD-461B

Published in 1980, this standard stream-lined the requirements by combining CE02 with CE01 and CE04 with CE03, and deleting RE04.  One notable addition to this standard was the A2a classification for "Spacecraft and Launch Vehicles (including associated ground support equipment)".  Another was the addition of the CE07 test, which specifies limits for the magnitude of power bus sag seen on an input power bus due to turn-on and the (back EMF) surge as a result of turn-off.  One can also see the increase in bandwidth in a number of the tests, most notably RS03 up to 40 GHz.

Test

Description

CE01

Conducted emissions, power and interconnect leads, 30 Hz to 15 kHz

CE03

Conducted emissions, power and interconnect leads, 15 kHz to 50 MHz

CE06*

Conducted emissions, antenna terminals, 10 kHz to 26 GHz

CE07

Conducted emissions, power leads, time domain

CS01

Conducted susceptibility, power leads, 30 Hz to 50 kHz

CS02

Conducted susceptibility, power leads, 50 kHz to 400 MHz

CS03*

Conducted susceptibility, intermodulation, 15 kHz to 10 GHz

CS04*

Conducted susceptibility, rejection of undesired signals, 30 Hz to 20 GHz

CS05*

Conducted susceptibility, cross modulation, 30 Hz to 20 GHz

CS06

Conducted susceptibility, power leads, transient spike

RE01

Radiated emissions, magnetic field @ 7 cm, 30 Hz to 30 kHz

RE02

Radiated emissions, electric field @ 1 meter, 14 kHz to 10 GHz

RE03*

Radiated emissions, spurious and harmonic emissions, 10 kHz to 40 GHz

RS01

Radiated susceptibility, magnetic field, 30 Hz to 30 kHz

RS02

Radiated susceptibility, magnetic induction fields

RS03

Radiated susceptibility, electric field, 14 kHz to 40 GHz

*limited applicability - applies to antenna ports only.

MIL-STD-461C

Published only six years after MIL-STD-461B, this standard was very similar to the B-version.  Notable among the changes made were a much more clear delineation between types of equipment being tested - each equipment type has its own part.  Also, this version added the damped sinusoidal testing of CS10 and CS11 as well as the RS05 requirement for electromagnetic pulse (EMP) field transient.

Test

Description

CE01

Conducted emissions, power and interconnect leads, 30 Hz to 15 kHz

CE03

Conducted emissions, power and interconnect leads, 15 kHz to 50 MHz

CE06*

Conducted emissions, antenna terminals, 10 kHz to 26 GHz

CE07

Conducted emissions, power leads, time domain

CS01

Conducted susceptibility, power leads, 30 Hz to 50 kHz

CS02

Conducted susceptibility, power and interconnecting control leads, 50 kHz to 400 MHz

CS03*

Conducted susceptibility, intermodulation, 15 kHz to 10 GHz

CS04*

Conducted susceptibility, rejection of undesired signals, 30 Hz to 20 GHz

CS05*

Conducted susceptibility, cross modulation, 30 Hz to 20 GHz

CS06

Conducted susceptibility, power leads, transient spike

CS10

Conducted susceptibility, damped sine transients, pins and terminals, 10 kHz to 100 MHz

CS11

Conducted susceptibility, damped sine transients, cables, 10 kHz to 100 MHz

RE01

Radiated emissions, magnetic field @ 7 cm, 30 Hz to 50 kHz

RE02

Radiated emissions, electric field @ 1 meter, 14 kHz to 10 GHz

RE03*

Radiated emissions, spurious and harmonic emissions, 10 kHz to 40 GHz

RS01

Radiated susceptibility, magnetic field, 30 Hz to 50 kHz

RS02

Radiated susceptibility, magnetic and electric fields, spikes and power frequencies

RS03

Radiated susceptibility, electric field, 14 kHz to 40 GHz

RS05

Radiated susceptibility, electromagnetic pulse field transient

*limited applicability - applies to antenna ports only.

MIL-STD-461D

The D-version of MIL-STD-461 was a major overhaul of this standard.  Both test levels and test methods were significantly changed, requiring an update to MIL-STD-462 as well.  Other than the notices which amended 462, this was the first major update to -462 since its initial publication in 1967.

So drastic a change was 461D that it changed all the test designators.  CE01 became CE101, CE03 became CE102, etc.  This allowed one to easily recognize that the new standard was being specified for a given program.

Test

Description

CE101

Conducted emissions, power leads, 30 Hz to 10 kHz

CE102

Conducted emissions, power leads, 10 kHz to 10 MHz

CE106*

Conducted emissions, antenna terminals, 10 kHz to 40 GHz

CS101

Conducted susceptibility, power leads, 30 Hz to 50 kHz

CS103*

Conducted susceptibility, intermodulation, 15 kHz to 10 GHz

CS104*

Conducted susceptibility, rejection of undesired signals, 30 Hz to 20 GHz

CS105*

Conducted susceptibility, cross modulation, 30 Hz to 20 GHz

CS114

Conducted susceptibility, bulk cable injection, 10 kHz to 400 MHz

CS115

Conducted susceptibility, bulk cable injection, impulse excitation

CS116

Conducted susceptibility, bulk cable injection, damped sine transients, cables and power leads, 10 kHz to 100 MHz

RE101

Radiated emissions, magnetic field @ 7 cm, 30 Hz to 100 kHz

RE102

Radiated emissions, electric field @ 1 meter, 10 kHz to 18 GHz

RE103*

Radiated emissions, spurious and harmonic emissions, 10 kHz to 40 GHz

RS101

Radiated susceptibility, magnetic field, 30 Hz to 100 kHz

RS103

Radiated susceptibility, electric field, 10 kHz to 40 GHz

RS105

Radiated susceptibility, transient electromagnetic field

*limited applicability - applies to antenna ports only.

One of the more significant changes in 461D was replacing the 10 uF feedthrough capacitors with Line Impedance Stabilization Networks (LISNs).  This change was implemented for all test setups, but the most significant impact it had was on the CE102 measurement.  Conducted emissions on power leads had previously been performed using a clamp-on current probe and the measurement was taken in terms of dB above one microamp.  (The current probe technique is still used for CE101.)  However, CE102 changes this measurement to one more similar to the commercial test method; namely, a voltage measurement taken off a coaxial port on the LISN.

Another change that was made to 461D version which was a significant improvement was specifying minimum sweep time requirements for both emissions and susceptibility testing.  Especially on susceptibility testing, this was a glaring hole in the previous standards.  By defining minimum requirements for sweep times (and also giving test labs the latitude to perform a step and dwell routine), the standards greatly reduced the possibility that susceptibility problems could be missed during testing.  Better definition in the standard also helped to ensure greater repeatability from lab to lab.

Next was the addition of making a pre-test calibration part of the test procedure.  When testing to the previous standards, one could go through an entire test suite with a faulty cable and never know it.  This cable could adversely affect the results for one or many tests, depending on how often it was used.  Performing a pre-test calibration is an excellent check to ensure that cables and connectors are in good condition, the correct transducer factors have been entered (with the correct signs!), and that all equipment is functioning within its required parameters to ensure that test results are within 3 dB of the intended level.

Finally was the abolition of narrowband and broadband measurements.  461D made no distinction between the two.  Instead, it specified a single emission limit that should be used and specified the measurement bandwidth of the receiver.  This was given as a function of frequency.  This change was also a significant step in the direction of the commercial standards and eliminated what had been a controversial and ambiguous part of the previous standards.

MIL-STD-461E

MIL-STD-461E is very similar to the -D version, with only a few changes.  Significant changes made are as follows:

  • The incorporation of MIL-STD-462 into 461
  • Minor changes in the RE and RS sweep times
  • Extension of CS101 from 50 kHz to 150 kHz
  • Reduction of CS114 from 400 MHz to 200 MHz

Test

Description

CE101

Conducted emissions, power leads, 30 Hz to 10 kHz

CE102

Conducted emissions, power leads, 10 kHz to 10 MHz

CE106*

Conducted emissions, antenna terminals, 10 kHz to 40 GHz

CS101

Conducted susceptibility, power leads, 30 Hz to 150 kHz

CS103*

Conducted susceptibility, intermodulation, 15 kHz to 10 GHz

CS104*

Conducted susceptibility, rejection of undesired signals, 30 Hz to 20 GHz

CS105*

Conducted susceptibility, cross modulation, 30 Hz to 20 GHz

CS114

Conducted susceptibility, bulk cable injection, 10 kHz to 200 MHz

CS115

Conducted susceptibility, bulk cable injection, impulse excitation

CS116

Conducted susceptibility, bulk cable injection, damped sine transients, cables and power leads, 10 kHz to 100 MHz

RE101

Radiated emissions, magnetic field @ 7 cm, 30 Hz to 100 kHz

RE102

Radiated emissions, electric field @ 1 meter, 10 kHz to 18 GHz

RE103*

Radiated emissions, spurious and harmonic emissions, 10 kHz to 40 GHz

RS101

Radiated susceptibility, magnetic field, 30 Hz to 100 kHz

RS103

Radiated susceptibility, electric field, 10 kHz to 40 GHz

RS105

Radiated susceptibility, transient electromagnetic field

*limited applicability - applies to antenna ports only.

Technical Notes Regarding Tailoring

One aspect of EMI testing for MIL-STD that has become much more prevalent in the past 15 years or so, has been tailoring of a given test standard to better reflect the anticipated environment that will be seen on a specific platform.  While this option is given to procuring agencies in versions B through D, it didn't really catch on across the board until the publication of the D-version.  While tailoring is more prevalent in the aerospace community, it may be seen in military procurement as well.

The consequence of this is the following admonition:  just because procurement specifies a particular MIL-STD requirement does not necessarily mean that you have to meet the published requirement.  The requirement may have been relaxed in some areas and, more important, it may have made more stringent in others.

Not reviewing the requirements carefully can result in a serious underbid of procurement.