modified 1998-08-11.

useful tools for electromagnetic compatibility (EMC), both (a) to measure how much your device radiates (EMI), to make sure it doesn't interfere with other devices, and (b) to generate radiation, to make sure your device doesn't flake out when placed near other radiators.

Also: (c) design tips and various components that improve EMC.

Note that this is woefully incomplete. Please help me flesh this out.


info on the "political laws" regulating the use of photons and electromagnetic waves.


Related pages:


electro-magnetic compatibility

I would like to know of ways to

-- i.e., improve my EMC ( electromagnetic compatibility ).

Here are a couple of ways I've found already; please help me find more.

Who regulates photons ?

Besides the physical laws that limit what you can do with photons, there are also bunches of legal limits to what you can do.

"Radio waves do not recognize political boundaries" -- Paul Cary.

  • [photons] http://www.howstuffworks.com/radio-spectrum.htm

    the spectrum of photons

    frequency chart; the electromagnetic spectrum

    [FIXME: lots of stuff scattered elsewhere] [I'm putting the spectrum here in emc_faq, rather than machine_vision, because in EMC it's nice to know exactly what frequency you're dealing with and what else is on that frequency ... and its harmonics ... while most machine vision stuff doesn't really matter which frequency, as long as the transmitter and the receiver agree.] [FIXME: maybe make an independent page out of this ?]


    Elektromagnum http://www.newphys.se/elektromagnum/ devoted to speculative electromagnetics and especially the possible explanation af gravity/inertia by EM.

    ELMA http://www.elma.com/ shielded enclosures

    some FCC labs http://www.act1.com/fcclab.htm

    Credence Technologies, Inc. http://www.credencetech.com/ EMC probes.

    FAQ: Sources of EMC and Safety Compliance Information http://world.std.com/~techbook/compliance_faq.html FAQ for the sci.engr.electrical.compliance newsgroup

    The Complete, Unofficial TEMPEST Information Page \ http://www.eskimo.com/~joelm/tempest.html lists one of the more ... controversial ... aspects of electromagnetic compatibility.

    Rubbercraft Corp. http://www.rubbercraftcorp.com/ EMI, RFI, and ESD shields

    International Mobile Telecommunications http://www.itu.int/imt/

    The IEEE Electromagnetic Compatibility Society http://www.emclab.umr.edu/ieee_emc/

    DAV's EMC FAQ info on the "political laws" regulating the use of photons and electromagnetic waves. (see also "DAV's Electromagnetic FAQ" for info on "physical laws")
    (need to read "Standards for Electromagnetic Compliance Testing" by Joe DiBartolomeo in 1997 May _Circuit Cellar INK_).
    from article "Spice predicts differential conducted EMI from switching power supplies" by Christophe Basso, Sinard, France. _EDN_ 1997 Feb 3. "line-impedance-stabilization network (LISN) ... As defined by international standard CISPR (International Special Committee on Radio Interference) 16 for EMI measurements, the LISN's impedance starts from nearly 5 &Ohm; at 10 KHz and rises to a constant 50 &Ohm; above 1 MHz. ... The actual LISN, which sits between the mains and the power supply under test, measures the differential and common-mode EMI signals that the supply generates. ... To reduce this noise below the electromagnetic-compatibility-standard limits, an EMI filter consisting of a single or multiple LC networks is necessary to isolate the mains from its polluter. ... the FCC Part 15 Class B rules, which require that the noise level stay below a flat line at the 48-dBuV level over a frequency range of 450 KHz to 30 MHz. ... However, for the stringent German VDE 0871 A/B, which the European standard EN-55022 replaces, or even for the CISPR 15 standard, the international rule for ballast applications, the curve is much more complex. ..."
    from article "Practical, inexpensive ways to reduce EMI in control systems" by David Brown, Engineer, Fisher-Rosemount Systems Inc., Austin, TX., vice chairman of the ISA SP71 committee. << Beginning January 1, 1996, control/computer systems sold in Europe must meet the most stringent electromagnetic compatibility (EMC) directive in the world. ...

    EMC Directive

    On January 1, 1996, the European Economic Community is scheduled to issue: * Cenelec EN 5008-1 (light industry) and EN 50081-2 (heavy industry) covering emissions. * Cenelec EN 50082-1 (light industry) and EN 50082-2 (heavy industry) covering immunity. These 2 standards generally follow the latest IEC and CISPR standards. Equipment certified to the EMC directive will carry the CE (Conformitˇ Europˇene) Mark.

    IEC 1326

    Draft IEC 1326... will become the international standard for EMC requirements for electrical equipment for control, measurement, and laboratory use. The standard consists of general requirements (1326-1), .... requirements for equipment used in laboratories or for test and measurement (1326-1:20).... It generally follows the EMC Directive and FCC standards and includes IEC Immunity Standards .... and CISPR Emission Standards ..

    ISA S71.05

    The ISA S71.05 draft standard will reflect the IEC 1326 standard with modifications appropriate to North America. >>
    from article "Practical, inexpensive ways to reduce EMI in control systems" by David Brown, Engineer, Fisher-Rosemount Systems Inc., Austin, TX. >> "When choosing heavy gauge ground conductors, consider welding cable. It's more flexible than conventional power cable, making it easier to install and therefore cheaper overall." "Most signal and communications cables -- and some power cables -- should be shielded, and their shields should be properly terminated ... Shields must be grounded ... and must be grounded at the power source end only. The other end should be cut, folded back, and taped off." "Self-generated cable noise can be noted in signal and communications cables serving moving equipment such as robots. As a solution, try using .... professional microphone cable, which is designed for long flex life and minimum self-generated noise." << Abbreviations: EMI: electromagnetic interference. EMC: electromagnetic compatibility.
    from Electrical Specifications of Apple Hardware (4/94) >> Article Reviewed/Updated: 1 April 1994 ... Additional Information ---------------------- "Current leakage" is the amount of current that is passed to earth ground. The current leakage of all Apple equipment meets the following specifications: - As specified by the UL standard for Apple equipment distributed in the United States, the current leakage will be less than 5.0 milliamperes. - As specified by the IEC 380 & 950 standards for Apple equipment distributed in France and most of Europe, the current leakage will be less than 3.5 milliamperes. ** The BTU calculation is Watts X 3.42 = BTU/hour. Copyright 1989-94, Apple Computer, Inc. <<
    Companies with EMC-related products: Chomerics division of Parker Hannifin (fax:?) (in Woburn, MA) sells Cho-Form automatic dispenser system that creates form-in-place conductive elastomer gaskets.

    A 5V peak-to-peak, 10 MHz clock line... has many harmonics ... one of which is a 450 mV 110 MHz signal ! Another is a 225 mV 220 MHz signal. ... square wave = cos(ωt) - cos(3ωt)/3 + cos(5ωt)/5 - cos(7ωt)/7 + ... ... one design problem is how to get a signal from one IC to the net without radiating these harmonics ... to other signal lines ... and ... to FCC compliance measuring devices ... the critical issue is rise time, not frequency ... ... The worst design to have is one that works most of the time. Good designers don't design to "acceptable" levels of noise immunity and margin. They design for the maximum possible noise margin, and, in doing so, they tend to have the fewest number of subsequent problems. ...

    -- Douglas Brooks, "Brookspeak: Designing for performance" article in _Printed Circuit Design_ Oct. 1996.

    "FCC is interested in worst-case operation ... 6 minute run." -- ?? "Electrodag is great as long as it's only assembled once, the electrodag doesn't flake, and it's never stressed by vibration etc." -- "Bruce" (??) "We often see problems with the 15th harmonic"
    Dexter Magnetic lots of interesting ferrite EMI suppressors.

    [FIXME: Doesn't the FCC keep the latest version of their regulations online ? Where ? Replace this obsolete version with a link to FCC.]
    Xref: agora alt.radio.pirate:3544 sci.electronics:66348
    Newsgroups: alt.radio.pirate,sci.electronics
    From:  (Rick Harrison)
    Subject: FCC Part 15 Rules FAQ
    Followup-To: poster
    Organization: The World Public Access UNIX, Brookline, MA
    Distribution: na
    Date: Thu, 8 Sep 1994 07:20:29 GMT
    Expires: Sat, 8 Oct 1994 23:59:00 GMT
    Lines: 217
    excerpts from FCC "Part 15" rules
    (Title 47 of the Code of Federal Regulations, Part 15)
    Subpart A -- General
    15.1 Scope of this part.
    (a) This part sets out the regulations under which an intentional,
    unintentional, or incidental radiator may be operated without an
    individual license.  It also contains the technical specifications,
    administrative requirements and other conditions relating to the
    marketing of part 15 devices.
    15.5 General conditions of operation.
    (b) Operation of an intentional, unintentional, or incidental radiator
    is subject to the conditions that no harmful interference is caused
    and that interference must be accepted that may be caused by the
    operation of an authorized radio station, by another intentional or
    unintentional radiator, by industrial, scientific and medical (ISM)
    equipment, or by an incidental radiator.
    (c) The operator of a radio frequency device shall be required to cease
    operating the device upon notification by a Commission representative
    that the device is causing harmful interference.  Operation shall not
    resume until the condition causing the harmful interference has been
    15.23 Home-built devices.
    (a) Equipment authorization is not required for devices that are not
    marketed, are not constructed from a kit, and are built in quantities
    of five or less for personal use.
    (b) It is recognized that the individual builder of home-built equipment
    may not possess the means to perform the measurements for determining
    compliance with the regulations.  In this case, the builder is expected
    to employ good engineering practices to meet the specified technical
    standards to the greatest extent practicable.  The provisions of 15.5
    apply to this equipment.
    15.35 Measurement detector functions and bandwidths.
    (b) ...When average radiated emission measurements are specified in the
    regulations, including emission measurements below 1000 MHz, there is
    also a limit on the radio frequency emissions, as measured using
    instrumentation with a peak detector function, corresponding to 20 dB
    above the maximum permitted average limit for the frequency being
    Subpart C -- Intentional Radiators
    15.207 Conducted limits.
    (a) For an intentional radiator which is designed to be connected to the
    public utility (AC) power line, the radio frequency voltage that is
    conducted back onto the AC power line on any frequency or frequencies
    within the band 450 kHz to 30 MHz shall not exceed 250 microvolts.
    Compliance with this provision shall be based on the measurement of
    the radio frequency voltage between each power line and ground at the
    power terminals.
    (c) The limit shown in paragraph (a) of this section shall not apply
    to carrier current systems operating as intentional radiators on
    frequencies below 30 MHz.  In lieu thereof, these carrier current
    systems shall be subject to the following standards:
     (1) For carrier current systems containing their fundamental emission
    within the frequency band 535-1705 kHz and intended to be received
    using a standard AM broadcast receiver: no limit on conducted emissions.
     (2) For all other carrier current systems: 1000 uV within the frequency
    band 535-1705 kHz.
    15.209 Radiated emission limits; general requirements.
    (a) Except as provided elsewhere in this subpart, the emissions from
    an intentional radiator shall not exceed the field strength levels
    specified in the following table:
                     |   Field strength       |   Measurement distance
    Frequency (MHz)  |   (microvolts/meter)   |   (meters)
    0.009-0.490          2400/F(kHz)               300
    0.490-1.705          24000/F(kHz)               30
    1.705-30.0           30                         30
    30-88**              100**                       3
    88-216**             150**                       3
    216-960              200**                       3
    Above 960            500                         3
    **Except as provided in paragraph (g), fundamental emissions from
    intentional radiators operating under this Section shall not be
    located in the frequency bands 54-72 MHz, 76-88 MHz, 174-216 MHz or
    470-806 MHZ.
      {Editor's note: paragraph (g) allows perimeter protection systems
      and biomedical telemetry devices to use the frequency bands 54-72 MHz,
      76-88 MHz, 174-216 MHz or 470-806 MHZ.  These are TV broadcast channels.
      No other unlicensed transmissions on TV frequencies are permitted.}
    15.215 Additional provisions to the general radiated emission limitations.
    (a) The regulations in 15.217 through 15.251 provide alternatives to the
    general radiated emission limits for intentional radiators operated in
    specified frequency bands.  Unless otherwise stated, there are no
    restrictions as to the types of operation permitted under these sections.
    15.217 Operation in the band 160-190 kHz.
    (a) The total input power to the final radio frequency stage (exclusive
    of filament or heater power) shall not exceed one watt.
    (b) The total length of the transmission line, antenna, and ground lead
    (if used) shall not exceed 15 meters.
    (c) All emissions below 160 kHz or above 190 kHz shall be attenuated at
    least 20 dB below the level of the unmodulated carrier.  Determination
    of compliance with the 20 dB attenuation specification may be based on
    measurements at the intentional radiator's antenna output unless the
    intentional radiator uses a permanently attached antenna, in which case
    compliance shall be demonstrated by measuring the radiated emissions.
    15.219 Operation in the band 510-1705 kHz.
    (a) The total input power to the final radio frequency stage (exclusive of
    filament or heater power) shall not exceed 100 milliwatts.
    (b) The total length of the transmission line, antenna and ground lead
    (if used) shall not exceed 3 meters.
    (c) All emissions below 510 kHz or above 1705 kHz shall be attenuated at
    least 20 dB below the level of the unmodulated carrier.  Determination
    of compliance with the 20 dB attenuation specification may be based on
    measurements at the intentional radiator's antenna output unless the
    intentional radiator uses a permanently attached antenna, in which case
    compliance shall be demonstrated by measuring the radiated emissions.
    15.221 Operation in the band 525-1705 kHz.
    (a) Carrier current systems and transmitters employing a leaky coaxial
    cable as the radiating antenna may operate in the band 525-1705 kHz
    provided the field strength levels of the radiated emissions do not
    exceed 15 uV/m, as measured at a distance of 47.715/(frequency in kHz)
    meters (equivalent to Lambda/2Pi) from the electric power line or the
    coaxial cable, respectively.  The field strength levels of emissions
    outside this band shall not exceed the general radiated emission limits
    in 15.209.
    (b) As an alternative to the provisions in paragraph (a) of this section,
    intentional radiators used for the operation of an AM broadcast station
    on a college or university campus or on the campus of any other
    education institution may comply with the following:
     (1) On the campus, the field strength of emissions appearing outside
    of this frequency band shall not exceed the general radiated emission
    limits shown in 15.209 as measured from the radiating source.  There
    is no limit on the field strength of emissions appearing within this
    frequency band, except that the provisions of 15.5 continue to comply.
    {Editor's note: they probably meant "continue to apply."}
     (2) At the perimeter of the campus, the field strength of any emissions,
    including those within the frequency band 525-1705 kHz, shall not exceed
    the general radiated emission in 15.209.
     (3) The conducted limits specified in 15.207 apply to the radio
    frequency voltage on the public utility power lines outside of the
    campus.  Due to the large number of radio frequency devices which may
    be used on the campus, contributing to the conducted emissions, as an
    alternative to measuring conducted emissions outside of the campus,
    it is acceptable to demonstrate compliance with this provision by
    measuring each individual intentional radiator employed in the system
    at the point where it connects to the AC power lines.
    (c) A grant of equipment authorization is not required for intentional
    radiators operated under the provisions of this Section.  In lieu
    thereof, the intentional radiator shall be verified for compliance with
    the regulations in accordance with subpart J of part 2 of this chapter.
    This data shall be kept on file at the location of the studio, office
    or control room associated with the transmitting equipment.  In some
    cases, this may correspond to the location of the transmitting equipment.
    (d) For the band 535-1705 kHz, the frequency of operation shall be chosen
    such that operation is not within the protected field strength contours
    of licensed AM stations.
    15.239 Operation in the band 88-108 MHz.
    (a) Emissions from the intentional radiator shall be confined within a
    band 200 kHz wide centered on the operating frequency.  The 200 kHz band
    shall lie wholly within the frequency range of 88-108 MHz.
    (b) The field strength of any emissions within the permitted 200 kHz
    band shall not exceed 250 microvolts/meter at 3 meters.  The emission
    limit in this paragraph is based on measurement instrumentation employing
    an average detector.  The provisions in 15.35 for limiting peak emissions
    (c) The field strength of any emissions radiated on any frequency outside
    of the specified 200 kHz band shall not exceed the general radiated
    emission limits in 15.209.
    They pretend to govern, and we pretend to obey.


    Design/Analysis Consultants, Inc. (DACI) http://www.cyberspy.com/~daci/ books on grounding and proper analog design

    optical power limiters

    limiting optical power, rather than radio power, uses very different techniques ... but I put it here since they're all photons.

    emc humor

    Newsgroups: sci.physics
    From: meron at cars3.uchicago.edu
    Subject: Re: Golden eye:007
    Organization: CARS, U. of Chicago, Chicago IL 60637
    Date: Wed, 29 Nov 1995 21:48:27 GMT
    Adam Whybrew <whybrew at physics.ox.ac.uk> writes:
    ><gt5542d at acmex.gatech.edu> (Ethan) wrote:
    >>I don't know how many of you have seen Golden Eye:007, but in the movie,
    >>the Russians have this weapon called "golden eye".  Its
    >>suppose to detonate a nuclear weapon in the upper atmosphere to create
    >>an electomagnetic storm over its target, causing every piece of electronic
    >>equipment to fry. I was woundering if this was  possible (considering this
    >>is a movie) and if so how powerful would the nuclear warhead have to be?
    >You don't even need a nuclear bomb. I work with a largish discharge excited
    >laser. When that fires the more sensitive electronic equipment in the room
    >immediately fries. It works - I've done it: to a thermometer, temperature
    >controller, video camera, and its power supply. You'd think I'd learn :-)
    >Unless my demands are met the UN building will disappear at noon...
    You may get a better offer if you say "Unless my demands are met
    the UN building won't disappear at noon..."
    Mati Meron			| "When you argue with a fool,
    <meron at cars3.uchicago.edu>	|  chances are he is doing just the same"


    From: < elvey at hal.COM> (Dwight Elvey)
    Newsgroups: sci.electronics.design
    Subject: Re: Audio 90 degree phase shift
    Date: 6 Dec 1995 02:48:49 GMT
    Organization: HAL Computer Systems, Inc.
    Lines: 20
    Distribution: world
    NNTP-Posting-Host: civic.hal.com
    ...  (Stephen G. Matzuk) writes:
    |> I'm looking for a topology that I can use to achieve a 90 degr. phase shift 50- 10,000 Hz.
    |> without shifting the phase of the other signal.
    |> Any sugggestions?
    |> Thanks.
    |> -Steve
    Hi Steve
     If you want to shift the hole spectrum 90 degrees simulaniously,
    you need what is called a Hilbert transfrom. Like many have said
    this is difficult to do with resistor and capacitors. It is
    quite easily done with a special type of FIR filter in DSP.
    Analog Devices, TI and Motorola all make development kits
    in the range of $89 to $150. I personally would recommend
    the ADI or Mot., as I believe these both have stereo codec's.
    From: cfindlay at netspace.net.au (Craig Findlay)
    Newsgroups: sci.electronics.design
    Subject: Re: New EMI regulations - January 96
    Date: Mon, 04 Dec 1995 05:09:18 GMT
    Organization: NetSpace Online Systems
    Lines: 41
    NNTP-Posting-Host: dialup-a2-4.mel.netspace.net.au
    X-Newsreader: Forte Agent .99c/16.141
    Andrew Holder <andrew at resmon.demon.co.uk> wrote:
    >I'm involved in designing and prototyping of small medical equipment.
    >The new European legislation on EMI looks pretty frightening. I don't
    >want to end up in jail!
    >Are there foolproof ways of designing so that you are well within the
    >requirements ? We already have substantial ground planes on all boards
    >and I intend to use screened cases. Maybe its then just a case of being
    >careful about signal inputs and outputs from the device.
    >I really don't have the sort of capital funding to be able to afford
    >even a day at most test houses and I certainly can't afford the
    >equipment myself.
    >Any advice on books etc. would be greatly appreciated. BTW, I'm not a
    >mathematician so it'll have to be fairly readable.
    There is an extremely good and readable book on this subject called
    Noise reduction in Electronic Systems, by Henry Ott. I don't have the
    ISBN number handy but let me know if you want it and I'll email it to
    I would advise you strongly to buy this, it has a solid math basis,
    but Ott carefully translates this into the real world with clear
    writing style and easy to understand diagrams, and the only formulas
    in the book are ones that even I can cope with. He also provides good
    Hope this helps,
    Craig Findlay <cfindlay at netspace.net.au>
    The Law, in its majestic equality, forbids the rich, as well as the poor,
    to sleep under the bridges, to beg in the streets, and to steal bread.
    --  Anatole France
    From: ft63 at dial.pipex.com (Peter)
    Newsgroups: sci.electronics.design
    Subject: Re: New EMI regulations - January 96
    Date: Wed, 06 Dec 1995 11:41:28 GMT
    Organization: UnipalmPIPEX server (post doesn't reflect views of UnipalmPIPEX)
    Lines: 30
    NNTP-Posting-Host: ai189.du.pipex.com
    X-Newsreader: Forte Agent .99c/16.141
    >Technically, it is the final system that has to comply.  The DTI product
    >standards guidline on EMC (April 1993) gives a definition of 'Apparatus'
    >(the item which must comply) as '..an electrical or electronic appliance
    >or system consisting of a finished product or products having an
    >intrinsic function which is intended for the end user, and is supplied or
    >taken into service or intended to be taken into service as a single
    >commercial unit.'
    I do not wish to minimise what you are saying, but sadly, the issues
    of "does it need to comply" and "does it need to comply to sell" have
    become quite separate, in the UK's crazy headless chicken EMC
    Everyone wants to see the CE mark on everything, even products which
    don't need it. This is because few people ever read the regs, and far
    fewer understand them.
    It is little use telling a customer "this product is exempted" because
    he will not understand. People want to see the CE mark on everything
    which does anything because they believe it protects them, somehow. I
    speak from 100% direct experience; I spend a lot of time every day
    talking to customers about this.
    I know a firm selling "CE marked" cables and gender changers... Soon
    we will have CE marked toilet rolls. This is getting like BS5750 in
    its early days (not many firms care much about it now, thank God).

    Started 1998 Jan 04

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    David Cary

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