Re: HALT/HASS Testing
Dwight: As you may be aware, there is a major push to use COTS (commercial off-the- shelf) hardware in military and space systems for non-critical (i.e., not life threatening or the equivalent for non-repairable spaceborne systems). The clear implication is that cool-running, functionally-efficient, state-of-the- art (i.e., designed and built with current, leading-edge technology) commercial designs are respectable in performance AND of high quality, while costing less than full mil-spec systems. With the exception of the actual test schedule/time, IF your designers have PROPERLY done their job AND your prototype construction is representative of your production quality for device heatsinking (or other cooling method) and solder connections, your company should benefit from HALT/HASS testing. It will serve to alert managers to incompetent designers and also (very importantly) avoid the reputation- and cost-damaging effects of multiple field failures. Field failures always directly affect a company's bottom-line profits. I recommend a full speed ahead attitude with the expectation that some weaknesses that NEED CORRECTING will be identified. Such testing gives designers a better perspective on the end use of the hardware, rather than just thinking in ones and zeros and only being terminal literate (one of my favorite phrases). Respectable hardware quality in the marketplace generally brings both professional AND monetary rewards to a company (Hewlett-Packard test and measurement equipment comes to mind). Good Engineering to you, Mike Conn Owner/Principal Consultant Mikon Consulting
Re: odd immunity problems ?
Lisa: Come to think of it, I have never seen a slot machine that wasn't encased in metal. Wonder if they use EMI gaskets?. Mike Conn Owner/Principal Consultant Mikon Consulting
Re: Company rewards for publishing
Jack: The comments by Rich Nute are right on the money. I would like to throw in another two cents worth. The pursuit of publishing has many direct benefits to the creating individual, although some may take time to surface. 1. The process of generating a written communication that will be read (and judged) by your technical peers forces you to be sure of your facts and/or state any reasonable limits on their applicability. This implied requirement sharpens your thought process, makes you double-check your information sources or research, and builds your confidence in your interpretation of technical data. 2. The same process improves your communication skills by the sheer practice of ferretting out the main points you wish to make, and by testing your grammatical skills. 3. If you take the conference paper route, you will gain experience in presenting to a technical audience. This experience will help you to prepare for and present your future ideas to corporate managers. All of these factors benefit your professional growth, which should ultimately be recognized in many ways, including financially. Hope this makes sense to you, Mike Conn Owner/Principal Consultant Mikon Consulting
Re: Emissions or not?
Tim: Your receiver frequency is very close to the third harmonic of your transmitter frequency. Perhaps the reflection off the adjacent car reinforced that harmonic to just exceed the rejection characteristics of the receiver. You might test that with a different (reflecting) car (with the same angular location relative to your vehicle) to see if it was a mixing/retransmitting phenomena or just a reflection (or something else!). By the way, great question re emissions during immunity. That would sure open a Pandora's box! Mike Conn Owner/Principal Consultant Mikon Consulting
Re: EMC/EMI finite element analysis package
This request may yield information beneficial to a large percentage of the PSTC community; therefore, I recommend responses also include Program name and supplier/vendor Platform it runs on (UNIX, DOS, Windows, other) Personal opinions of usefulness, limitations, speed of operation, ease of use and ease of learning, etc. Mike Conn Owner/Principal Consultant Mikon Consulting
Re: 60Hz EM fields
Chuck: There is a comprehensive review and assessment of studies on this subject presented in the Oct. 1995 issue of the IEEE Spectrum probably the most trustworthy survey source for this type of information. The EMC Society Newsletter (issue #168, winter 1996) had a brief comment on a 10-year study conducted by the National Council on Radiation Protection and Measurements that recommended housing, schools, etc. not be built under power lines IF FIELDS EXCEED 0.2 microtesla. National Geographic did a 1-hour special that essentially said no problem, inadequate correlation, and criticized the multi-billion dollar impact such unfounded fears have had on the US economy to date. I have lived under power lines for the last 20 years with no reports of my neighbors having any negative effects. In fact, I have measured the fields in and around my home (which is centered about 70 feet off the axis of the high voltage lines supplying the substation that is approximately 100 feet from my house). I found the fields OUTSIDE to be well under 0.1 microtesla; however, I measured many locations over a HUNDRED times higher INSIDE the home. Areas near refrigerators, fluorescent lights, clock radios, etc. ALL produced fields much greater than those generated by the outside power lines. The relative placement of the power lines on the support structure to achieve field cancellation is probably most important in providing compatibility of power distribution systems. It seems the housing construction standards (and perhaps electric appliances) are far more in need of the public's concern about the biological effects of low-frequency magnetic fields. Mike Conn Owner/Principal Consultant Mikon Consulting
Re: Frequency Spectrum Chart
A couple of years ago, Motorola generated a (free) chart that was distributed through PENSTOCK, a distributor, that identified nine categories of RF use and covered the 500 kHz to 4 GHz range. The specific frequency bands used by each of the nine categories are indicated along with their specific function. It is about three feet wide and 16-18 inches tall. You might try calling 1-800-PENSTOCK to see if they still carry it. Perhaps someone else can identify charts for the higher frequencies. Mike Conn Owner/Principal Consultant Mikon Consulting
Re: EMI Site Interference
Scott: Here's a couple of comments and suggested possibilities to investigate in tracking down the source of your problems. 1. Check the turn-on time (not X-ray operation time) for the X-ray equipment. The operator may turn on the unit, take one exposure, change film and set up for a second exposure, take the second exposure and then shut down the unit. That might account for the one minute (or so) duration. 2. Check out any low-power, automatic, motor-driven vent controls in your air conditioning system that may (only occasionally) come on during the day. Noisy, brushed motors may be used for such operations. 3. Don't rule out local sources generating power line conducted emissions yet. When the interference appears, quickly switch to a current probe and sense the AC line cord noise/current. Note the levels during and after the interference. Your AC line filter internal to the spectrum analyser may preclude detection when you disconnect the signal input cable. If suspicious current differences are noted, resume your search internal to the company. 4. Check to see if there are any pump controls nearby for storm drainage flow control (or other flow control, such as irrigation). These units are periodically polled from a remote control site (or operate on timers), and transmit a status to the remote site via RF links. I have such a slave valve site approximately 150 feet from my home and experience periodic bursts of interference (for 60 to 70 seconds) on multilple TV channels. Good luck, Mike Conn Owner/Principal Consultant Mikon Consulting
Re: Spira EMI Gaskets
Brian: Spira is a company in North Hollywood, CA, whose primary product is a soft- core, compressible material spirally wrapped with a conductive metal. The product has a trade name of Flexi-Shield. Different cores and metals are available. You can reach them at (818)764-8222 for a free design guide and sample kit. They claim superior sealing for sliding applications (e.g., VME front/rear panels). Mike Conn
Spira EMI Gaskets
I just caught Ed's comment on the use of Spira gaskets. I have recommended their POSSIBLE use to one of my clients for sealing around some single-board computer VME cards; however, I have not directly evaluated the performance of Spira gaskets. Their literature makes great claims (up to 130 dB SE out to 1 GHz), but has any of our readers personally evaluated their effectiveness? Thanks for your time, Mike Conn Owner/Principal Consultant Mikon Consulting
Re: Re[4]: Upcoming EMC Seminar
My two cents worth A brief announcement (perhaps on where to obtain more details) on upcoming seminars (whether or not for $) is a service to those who need the exposure/training. Such advertising to members of our community helps lower the cost of those seminars to us (the recipients). Improvement of the skills and understanding of our participating community earns respect and reflects well on the entire community. Those members who trust only in the techniques they have personally witnessed are perhaps only cut and try artists. Hence, we all should stay on the trail of continually acquiring updated knowledge and new analysis techniques that will benefit our futures. As a practical matter, basic EMC material must be presented in seminars to assure the group follows the rationale of more advanced techniques that are generally presented in the latter portions of the seminar. Otherwise, you lose the audience. The demonstration of the many techniques normally presented in an EMC seminar would double or triple the presentation time and cost for the effort. Nevertheless, a sound (convincing) basis for offered techniques should be a prerequisite for inclusion in a seminar. Since the clients for whom many techniques (particularly new, little-known ones) proved beneficial in time-to- market and/or superior performance prefer to keep them CONFIDENTIAL, a professional consultant cannot disclose all the performance details without risking legal action and perhaps his/her future career. The alternate (i.e., reconstructing the techniques on a sanitized test item) is prohibitively expensive. My comments come from having prepared and given many seminars (for $) over the last eight years. I enjoy sharing my knowledge and solving the really tough EMI problems. And, I earn good money doing so. HOWEVER, I have made virtually no money on just giving seminars alone. Hope these thoughts didn't bore you... Mike Conn Owner/Principal Consultant Mikon Consulting
Resend: Ferrite Bead Saturation Effects
Since I haven't yet received my copy of the original transmittal I sent on 22 January, it must have fallen into an electronic crack somewhere. Hence, here goes a second time. MLC Gentlemen: Because of the intended lossy nature of the various ferrite bead formulations, the difference (if any) of the RF loss characteristics versus frequency as a function of the direct current (or more accurately, the flux density) in the bead is not well publicized (if reliably known at all). .Another way to characterize this behavior might be to assess the loss factor of the material versus dc current and frequency and correlate this to the (generally published) permeability data. Can anyone supply me some data or direct me to some authoritative literature/papers on the subject? I have tested, characterized, and modeled specific beads planned for specific circuits and know the bead formulation, size, and temperature will all have their respective effects. However, is there an easier way to reliably execute a design without actual test characterization of a given circuit (and specific bead) configuration? Thank you for your time and consideration. Mike Conn Owner/Principal Consultant Mikon Consulting
Re: Values for hazardous currents.
Rich: Thanks for the excellent commentary. As I originally noted, my input was from about 20 years ago (and it could have been a subjective judgement/guess at that time by the Dr. teaching the course). I think we all have benefited from the discussion of this subject in that we need to clearly think out all facets of a potential safety issue. That is, how the safety concern arises, the physical connections to a person, the electrical paths involved, the impedance magnitudes involved, and the susceptibility levels asociated with those particular conditions. Mike Conn Mikon Consulting
Re: (off topic) GFI history.
Hi all. From data presented in a Stanford University course on Electronics in Medicine approximately 20 years ago, heart fibrillation could be induced by passing only 1 mA directly through the heart muscle. When considering all the parallel current paths around the heart for an external exposure to a (potentially lethal) source voltage, the dangerous current threshold could easily vary from 5 mA (e.g., for a connection between a person's two hands) to hundreds of millamperes, depending on the source and return connection points on the body. Because of this potential range of current, some standards group has made a subjective judgement (5 mA for US GFIs) that many other groups would not have made. If not prohibitively expensive because of inadequate technological solutions, it's better to be on the safer side of low trip currents. I agree with an earlier comment about the infrequency of nuisance tripping; i.e., low current thresholds are NOT a problem unless the circuits are degraded in the first place. Just my two cents worth, Mike Conn Owner/Principal Consultant Mikon Consulting
Re: Antenna Calibration/Site Attenuation
Good comment, Ed. We all depend on our reputations as competent technical people that we can deliver the best product or service reasonable. Proper or deficient equipment can make or break (respectively) the quality of our well-intended work. Hence, knowledge of any weaknesses in a particular piece of equipment (in this case, an antenna) can at least allow us to investigate and compensate for the known weakness. A potential benefit of reporting anomalies with a particular piece of equipment is the bringing forth of comments from the (defending) manufacturer. The manufacturers normally will have performed exhaustive analysis and corroborative characterization on a given antenna during its development phase, but seldom will the users get access to that data unless the need to publish it arises. We may all learn how to identify more subtle anomalies, fix them, or compensate for them. I haven't noticed any antenna vendors jumping into the discussion on antenna characteristics, and we all know they read this forum daily. How about it, guys? Mike Conn Mikon Consulting
Re: Graphics Conversions
Jim (and others): All the common file formats are easily handled on the PC up to megabytes in file size by a shareware program called XFERPRO. As a consultant, I have dealt with electronic transfer via modems and over the internet for years with more than 200 companies. XFERPRO works, is dirt cheap (I paid $10 about a year ago) and can be downloaded off the internet for a free trial period. You don't have to use both a PC and a UNIX platform for the different formats, the PC can handle all of them and detects their encoded formats automatically. On the net, go to Sabasoft.com for all the details. They now have a 32 bit version as well as the 16 bit version. XFERPRO requires Windows 3.1, Windows for Workgroups 3.1/3.11, or Windows 95 and NT. XFERPRO will not run under Windows 3.0. The following table is an indication of the file types that are handled by XFERPRO. Pardon the non-aligned columns, but I would have to ATTACH A FILE to make the columns line upbut that's the point of allowing file attachments, right? File Format Encode Decode Methods ChecksumMultiple Enclosures _ Single File Y Y UU, XX Y Y Single File Y Y MIMEY Single File Y Y Binhex 4.0 CRC-16 SimTel File Format Y Y UU, XX Y Comp.binaries Usenet Newsgroup Y Y UU, XX Y Alt.binaries Usenet Newsgroup 1 Y Y UU, XX Y Alt.binaries Usenet Newsgroup 2 Y Y UU, XX Y Alt.binaries Usenet Newsgroup 3 Y Y UU, XX Y Alt.binaries Usenet Newsgroup 4 Y Y UU, XX Y UNIX Shell Archive Y Y UU, XX DOS R.E.M v5.24 Y Y UU, XX Y X-File File Format Y Y UU, XX Y UUXFER version 2.0 Y Y UU, XX Y WINCODE version 2.3 Y Y UU, XX Y POST version 1.2.0 Y Y UU, XX Y POST version 2.0.1 Y UU, XX xmitBin Y Y UU, XX Y BITFTP Archive Y Y UU, XX Y Squirrel 3.0Y UU, XX America On-Line Y UU, XX ** Another option, Windows users can use the freeware application WinCode, available from A HREF=http://www.members.global2000.net/snappy/software.html http://www.members.global2000.net/snappy/software.html/A. Macintosh users can use the shareware application Decoder , available from A HREF=http://w ww.concentric.net/~Columbin/http://www.concentric.net/~Columbin//A. Hope this helps. Mike Conn Owner/Principal Consultant Mikon Consulting
Re: Graphics in posts
Gentlemen: I too often have seen entire groups bored stiff and intellectually stymied by moving at the pace of the most deficient member of a learning group. A perfect example is the California school system that currently ranks about 49th in the USA. To limit the use of (not so) new tools is obscene. We are in an acknowledged black art area because of the technical difficulties in modeling, measuring, predicting, and understanding the myriad of factors that affect electromagnetic fields. We NEED the best tools and we NEED the best communication methods and we NEED to use collective synergism of our individual experiences to forward our professions. With these thoughts in mind, we need to be PRUDENT in what is uploaded by using our common sense. Other than that, please do not put more regulatory requirements on what I have observed to be a lucid, information-sharing group that represents the field of EMI Engineering well. Mike Conn
