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Product Safety Newsletter •

TheProductSafetyNewsletter

®

Vol 2, No. 1 January-February 1989

Chairman’s Message

In this issue Page

Chairman's Message Richard Pescatore 1

Committee Scope 2

Technically Speaking Rich Nute 3

News and Notes Dave Edmunds 8

Ask Doctor Z Doctor Z 10

Area Activity Reports 11

Quality vs. Safety Manning I. Rose 13

Editorial Roger Volgstadt 16

European Compliance John McBain 17

Calendar Back Cover

It seems hard to believe, but herewe are, at the beginning of anothernew year. Reflecting back on 1988,I have to say that the ProductSafety Technical Committee had agood year. Indeed, a revolutionaryyear.

We entered 1988 as a newlyformed, single chapter of a group,calling ourselves the Product SafetySociety. We had developed acharter, a strategy to implement thecharter, and had established a set oforganizational objectives (toaffiliate with the IEEE, remem-ber?). Enthusiasm was in the air.

In February, the fIrst issue of ournewsletter was published anddistributed to about 150 people.Also in February, a second chapterwas formed in the NorthwestemU.S.

By July, the newsletter circula-tion had exceeded six hundred.Four chapters were active nation-wide.

In August, the first step in ourquest for becoming an IEEESociety was realized as the IEEE

EMC Society Board of Directorsvoted to allow us to affiliate withtheir group as the Product SafetyTechnical Committee (PSTC).

At their November meeting, theIEEE EMC Society Board ofDirectors approved our CommitteeScope (see next page) and con-firmed our officers.

The end of December saw uswith a newsletter circulation ofgreater than eight hundred, a grow-ing organization, and a need forrevenue and volunteers.

Enthusiasm is still in the air. ThePSTC is still growing at a rapid rate.Several new local groups are in theformation stages. One (in Chicago)has set a date for its first meeting.

But, your help is still needed. Wespecifically need volunteers to serveas the Symposium Liaison Chair-man and the Standards LiaisonChairman. These positions arecritical and need to be filled imme-diately. In addition, we need volun-teers to serve on variouscommittees. Your contributionis required for our group to be

successful. Please call, write, orsend a fax to one of the officerswith your area of interest.

We are also still in need of rev-enue to help support the newsletter,which is our single biggest expense.We are looking at various ways togenerate funds and to lower ourcosts.

Some ideas to fund the news-letter are to solicit contributions(contributors will be recognized inthe newsletter), obtain funds fromthe EMC Society, obtain fundsfrom the individual chapters, andcharge a fee for the newsletter.These, as well as other thoughts,are under consideration. Yoursuggestions will be appreciated.

The year 1989 will no doubtbring about new challenges. Butyour officers and committee chair-men, with your help, are ready tomeet these challenges and tocontinue our efforts to “... advancethe awareness of product safety...”

Best wishes for a prosperousyear.

Rich Pescatore, Chairman



The Product Safety News-letter is published bimonthlyby the Product Safety Techni-cal Committee of the IEEEEMC Society. No part of thisnewsletter may be reproducedwithout written permission ofthe authors. All rights to thearticles remain with theauthors. Opinions expressedin this newsletter are those ofthe authors and do not neces-sarily represent the opinionsof the Technical Committee orits members. Comments andquestions about the newslettermay be addressed to theProduct Safety Newsletter,Attention: Roger Volgstadt, c/oTandem Computers, 2550Walsh Ave., Santa Clara, CA95051-1392, Fax No. (408)748-2137.

This newsletter is preparedby the Corporate GraphicsGroup of Tandem ComputersIncorporated. The editor wishesto extend a special thanks toAnnie Valva and Jodi Elgin ofTandem Computers for theirwork in preparing this newsletter.

EditorRoger VolgstadtNews EditorDavid EdmundsTechnical EditorJohn ReynoldsAssistant EditorJohn McBainPage LayoutKen WarwickSubscriptions ManagerJohn McBain (acting)

Vol 2, No 1 January/February 1989The following is the PSTC Scope that was approved at the Novem-ber 16,1988 meeting of the EMC Society Board of Directors meeting.

Committee Scope:The TC on Product Safety is concerned with the electrical safety (bothdirect and indirect) of electronic products. The Committee strives toadvance the knowledge and awareness of product safety through:• Study of product safety engineering principles and applications,

including those related to EMC.• Promotion of consistent understanding and interpretation of appli-

cable product safety standards.• Understanding of the contribution to product safety of the test house.• Understanding of the certification processes.• Review of emerging standards.• Study of the implementation of product safety principles within

organizations.

It is anticipated that the Committee will carry out the above throughenhanced communications and education. The following methods maybe used to this end:• Sponsor presentations and panel discussions by technical experts.• Publish pertinent papers and articles in IEEE publications, including

the EMC Society Newsletter (in cooperation with the appropriateeditors).

• Publish a periodic newsletter.• Prepare and review papers relating to the safety of electronic products

for presentation at EMC symposiums.• Provide safety engineering information to standards writing groups

within the society and other organizations.• Provide information based on industry practices to certification

agencies.

Product Safety Technical Committee Scope


Hello from Vancouver,Washington, USA:

One of our members suggestedI write about thermocouples andtemperature measurement. Text-books have been written on thissubject; I can only give a broadoverview of the subject. Sincetemperature measurement is indig-enous to every safety evaluation,perhaps I can demystify some ofthe rules applied by the variouscertification houses.

Disregarding accessible hotpans, why do we measure tem-peratures, and how do we decidewhat pans should be measured?What is the hazard that is pre-vented, controlled or limited as aresult of measuring temperatureswithin electronic equipment? Whydo we measure temperature riserather than absolute temperature?

Why do we use thermocouplesrather than other temperaturemeasuring devices? And, how dothermocouples work?

Thermocouple TheoryLet’s tackle this last question first.According to ANSI MC96-1, athermocouple is “two dissimilarthermo elements so joined as toproduce a thermal emf when themeasuring and reference junctionsare at different temperatures.”

Technically Speaking

Thermocouples andTemperature Measurement

This definition has three criticalconcepts in it: “thermoelements,”“thermal emf,” and “junction.”The most critical concept is that of“thermal emf.”

In 1821, Thomas JohannSeebeck discovered that, in aclosed circuit made up of twodissimilar metals (thermoele-ments), electric current will flow ifthe temperature of one junction iselevated above that of the other.This phenomenon is known as the“Seebeck effect.” (See Figure 1.)The “circuit” comprises a thermo-couple. All dissimilar metals ex-hibit this effect.

Note that every wire has twoends. When connected into a cir-cuit, every wire has two junctions,one at each end of the wire. Wherea junction involves dissimilarmetals, the wires become thermoe-lements. Where both junctionsinvolve dissimilar metals, the

system becomes a thermocouplewhere one junction is the “meas-uring junction,” and the other endis the “reference junction.”

Each thermoelement junctiongenerates a voltage (thermal emf),proportional to temperature. Whenthe two thermoelement junctionsare at the same temperature, thethermal emf’s are equal, and thereis no current in the circuit. Whenthe temperature of one junction ishigher or lower than the otherjunction, the ammeter will indi-cate a current which is propor-tional to the temperature differ-ence between the two junctionsand to the areas of the junctions.

(The tricky pan of the system isto connect the meter in such afashion as to neutralize the effectof nonmeasuring junctions ofdissimilar metals. More about thislater.)

Rich Nute

Continued

J1-Measuring Junction at unknown temperatureJ2-Reference Junction at known temperatureI-Current proportional to temperature difference between J1 and J2


Technically SpeakingContinued

Figure 2 is an equivalent circuitto Figure 1. Each junction can be re-presented by a battery and resistorin series. In Figure 2, thermalemf’s Eland E2 are a function ofthe combination of different metalsand proportional to the tempera-tures of the junctions. ResistancesR1 and R2 are proportional to thearea of the respective junctions.

In Figure 2, I is proportional tothe temperature difference betweenJunction 1 and Junction 2. But I isalso proportional to the values ofR1 and R2. The values of R1 andR2 are proportional to the areas ofthe junctions, which are neitherpredictable nor repeatable. There-fore, while I is proportional to thetemperature difference, it cannot beused to determine temperaturedifference unless the values of R1and R2 are determined and ac-counted for.

We can eliminate the effects ofR1 and R2 by replacing theammeter with a voltmeter. SeeFigure 3. The voltmeter measuresthe voltage difference E + E 1 - E2,between the two junctions. If weknow the temperature of the ref-erence junction, then we can deter-mine the voltage E2 by lookingup, in tables, the voltage thatcorresponds to the reference junc-tion temperature. Now, we cansolve the equation E1 = E + E2.We now go back to the tables andlook up E1 and its temperature,which is the measuring junctiontemperature.

If the reference junction tem-perature is at 0 deg. C (in an icebath), then, since the voltages inthe tables are referenced to 0 deg.C, E2 = 0, and E = E 1. Now, wecan eliminate the summing step,and just read the temperaturedirectly from the tables.

Voltmeter JunctionsNow the question: How do we dealwith the connection (junctions) ofthe iron wire to the copper wires ofthe meter? Recall two statements:First, all dissimilar metals exhibit

the Seebeck effect. Thus, theconnection from the iron wire tothe two copper wires constitutesanother thermocouple. Second,when two junctions are at the sametemperature, the thermal emf s areequal, and there is no current inthe circuit. So, we put the two iron-copper junctions on an isothermalblock so that the temperature ofone junction is the same as thetemperature of the other junction.(See Figure 3.) Thus, the two

Continued



additional junctions cancel out,and do not connibute to the meas-urement.

Reference Junction TemperatureThe temperature of the referencejunction needs to be determined.There are several ways to do this.

First, we can force the junctionto a particular temperature. Themost obvious is the ice bath. Butthis is cumbersome.

Or, second, we can put the refer-ence junction onto an isothermalblock and measure the temperatureof the block by some other means.This is commonly done with athermistor.

Or, third, we can use a batteryand thermistor circuit to generatethe same voltage as if the referencethermocouple was at 0 deg. C.This is the “electronic ice point.”

In each case, and possible aftersome intermediary steps, the resultis the voltage (proportional to thetemperature) of the measuringjunction. The next step is to con-vert the voltage to a temperature.

Voltage-to-TemperatureConversionFirst, we can simply look up thevoltage in a table, and read thecorresponding temperature. Thiscould be done either manually orwith an electronic memory.

Or, we can calculate the tem-perature from an equation of therelationship between voltage and

temperature.Or, we can assume the voltage-

to-temperature relationship islinear, measure voltage, employ ascale factor, and read out tempera-ture (with some inaccuracy).

(The voltage-to-temperaturerelationship of a thermocouple isnot linear. The Type K thermo-couple approaches linearity over atemperature range of 0 to 1000deg. C and is the thermocouple ofchoice for use with a scalingvoltmeter.)

Fortunately, most modern-daythermocouple measuring equip-ment addresses all of these para-meters so that we need not con-cern ourselves with meter junc-tions, isothermal blocks, referencejunctions, reference junction tem-perature, voltage-to-temperaturerelationship, or nonlinearity. Weneed only apply the thermocoupleor probe to the object and readtemperature.

Thermocouple TypesThere are many different thermo-couple types, and the more com-mon types have been standardizedby letter designation and colorcoding of wires, connectors, andisothermal junction blocks. Certi-fication houses have standardizedon the Type J thermocouplebecause it is inexpensive and,therefore, popular and readilyavailable, and it has a suitabletemperature range.

Despite this standardization,mixups occur. A cup of ice waterwill not show a mixup of thermo-couple types since, by convention,0 deg. C corresponds to 0 V for allthermocouple types. Instead, a cupof boiling water confirms whetherthe system is homogeneous andcalibrated.

Thermocouples vs. OtherThermometersWhy do we use thermocouplesrather than other temperature-meas-uring devices? Certainly one of thereasons is that thermocouples havebeen around for a long time and arewell-characterized in their perform-ance. By standardizing on oneparticular system, thermocouples,one of the variables in temperaturemeasurement is eliminated.Thermocouples, in general forsafety evaluation, have relativelylow thermal mass compared to thepart being measured. This is neces-sary because a thermocouple alwaystakes heat away from the objectbeing measured, and lowers thetemperature by some amount. Tominimize this error, we use thesmallest thermocouple practicablefor the particular measurement.CSA, for example, specifies No. 30A WG thermocouple wire with awelded junction.

Thermocouple AttachmentThe attachment of the thermocoupleto the part to be measured is also

Continued



critical to an accurate temperaturemeasurement. The thermocouplejunction must be in direct contactwith the pan or material beingmeasured. This means that, ifepoxy cement is used to attach thethermocouple, there must be nocement between the thermocoupleand the pan. Otherwise, there is atemperature gradient through thecement. The thermocouple willmeasure the temperature at itslocation within the epoxy whichwill, necessarily, be less than thatof the pan being measured.

In some cases, the epoxy orother attachment means may act asa thermal insulator for the pansuch that the temperature meas-ured by the thermocouple isactually higher than the tempera-ture without the epoxy or otherattachment means.

The general rule is: use the leastamount of material practicable forattaching the thermocouple to thepan.

HazardsWhat is the hazard that is pre-vented, controlled, or limited as aresult of measuring temperatureswithin electronic equipment? Thisis not at all intuitively obvious, noris it obvious from a study of thevarious certification-house stan-dards. We begin to get an idea ofthe hazard from the title of Clause7.2 of IEC 348, “Safety Require-merments for Electronic Measuring

Apparatus.” The title: Preservationof Insulation.

The principal objective oftemperature measurement is todetermine that all safety-relatedinsulations are used within theirtemperature ratings. When this isaccomplished, we can be assuredthat the insulation is not undulystressed by the temperatureimposed upon it, and that, there-fore, it will be “preserved.” A fun-damental assumption is that if theinsulation is used within its tem-perature rating, it is not likely tofail--- that is, it is preserved ---for its lifetime.

The hazard that is prevented isthat hazard that would result fromthe failure of the particular insula-tion. Often, insulation failureresults in conditions for electricshock. Insulation failure in elec-tronic equipment may also resultin electrically-caused fire.

MeasurementsNow we can begin to decide whatpans should be measured. Obvi-ously, we measure all safety-related insulations. This wouldinclude transformers, inductors inmains circuits, printed wiringboards, switch bodies, thermoplas-tic-insulated wires, etc.

But, in a transformer, we meas-ure the wire temperature, not theinsulation temperature. Why? Thewire temperature heats the insula-tion, and since the wire is in inti-mate contact with the insulation,

the wire temperature is the worst-case insulation temperature. And,most electrical insulators are alsothermal insulators, so measuringthe hottest spot on the insulation isdifficult, if not impossible.

In some standards, we are re-quired to measure semiconductordevices and resistors. Why do wemeasure these components sincethey are not a safety insulation? Wedo so because wire insulation couldcome in contact with the devicesand be burned.

We also measure polymericmaterials and capacitors. Polymericmaterials are used as enclosuresand structures. Here, too, thematerial must be “preserved” toretain its enclosing and structuralfunctions; preservation is accom-plished by using the material withinits ratings.

Electrolytic capacitors are sub-ject to explosion if the temperatureis too high, so we measure theirtemperature. However, most oftoday’s modem capacitors are pro-vided with pressure relief mech-anisms, but the requirement hangson. X and Y capacitors are essen-tially across-the-line and line-to-ground insulations which must beused within their temperatureratings if the insulation is to bepreserved.

Temperature RiseWhy do we measure temperaturerise rather than absolute

Continued



temperature? This is a difficultquestion based on the precedingdiscussion. In the precedingdiscussion I implied that eachmaterial, whether insulation,polymeric material, or electrolyticcapacitor, will fail to perform itsfunction at some absolute tempera-ture. If our objective is to obviatefailure by operating insulations,polymeric materials, electrolyticcapacitors, etc., within theirratings, then we should be con-cerned with absolute temperatures.

The problem with absolutetemperature is that if we shouldmeasure temperature in a 20 deg.C environment, and someone elseshould measure temperature in a25 deg. C environment, then ourmeasurements may show accept-able performance, while theirmeasurements may show unac-ceptable performance. But, if wesubtract the ambient temperature,we both will get very nearly thesame number.

The temperature-rise limitsspecified in standards are conser-vative when compared to ratedtemperatures of insulations, etc.And, they assume that the ambienttemperature will be in the neigh-borhood of 20 to 25 deg. C. Forexample, a typical Class 105insulation is allowed to rise 65deg. C. So, if ambient is 25 deg. C,

the absolute temperature is 90deg. C, comfortably below the105 deg. C rating.

Temperature-rise measure-ments and limits are used for thepurpose of standardizing measure-ments between parties when theambient is not closely controlled.-------------------

Due to space limitations, I havecovered only a limited number of detailswithin this subject. My selection ofsubjects is based on my personalexperiences (or, rather, problems)encountered in temperature measure-

ment and the use of thermocouples.Those with extensive background andexperience may feel that I have omittedimportant points; if so, they are invitedto make those points known in letters to:Editor, Product Safety Newsletter, c/oTandem Computers. 2550 Walsh Ave..Santa Clara. CA 95051-1392.


News and Notesby Dave Edmunds

Place your company’s name here by making

a contribution to the

Product Safety Newsletter.Contact the Product Safety Newsletter Editor for details.

(see return address on cover)

NewslettersThere are several newsletters thatmay be of interest to a productsafety engineer. Subscriptioninformation is included.

TUV Rheinland Product SafetyNews is a publication prepared byTUV Rheinland Group Asia whichincludes a listing of German safetystandards. Copies are availablefrom offices of TUV in Japan,Taiwan, Korea, or Hong Kong. Noinformation is available on cost orfrequency of publication. Only anaddress for the Hong Kong officeis listed here: TUV RheinlandHong Kong Ltd., Suite 2906, 29thFloor, Three Exchange Square, 8Connaught Place, Central HongKong.

VDT News is a bimonthlypublication that lists items on VDTsafety and ergonomics. Cost is$87.00 per year from VDT News,P.O. Box 1799, Grand CentralStation, New York, NY 10613.The editor is Louis SeIsin, Ph.D.Some items of interest in the latestissue include: a status of thepreliminary injunction prohibitingenforcement of the VDT lawissued by Suffolk Co.; the status ofVDT state and local laws or docu-ments with names and addresses tocontact for more information; and asummary of NIOSH workshopson ergonomics and VDTs.

Product Safety Letter is aweekly publication that has sum-maries of the activity of the

Consumer Product Regulations.Circulation information is fromConsumer Product Regulations,117 N. 19th St., Arlington, VA01798, phone (703) 247-3433.

IEC Bulletin is an IEC publica-tion summarizing the variousactivities of the IEC. Included area calendar of events, committeereport, status of six-month ruleddocuments, and recent publisheddocuments. The IEC Bulletinyearly subscription is Fr 21 forordinary mail or Fr 30.50 forairmail from mc, 3 Rue deVarembe, P.O. Box 131, 1211Geneva 20, Switzerland.

Readers’ Feedback WantedThis is the third appearance ofthis column, and we are seekinginput from the readers. Does thiscolumn contain information thatis interesting? Please advise us ifthere are other types of informa-tion that you would find interest-

ing. If you know of any periodi-cals that deal with product safety,please send us their addresses. Ifyou have ideas, suggestions,information you want published,or wish to assist or supply mate-rial, please contact Dave Edmunds,Xerox Corp., 800 Phillips Rd., MS834-16S, W. Webster, NY 14580or phone (716) 422-2380.

Laser StandardTwo additions to the Z136 seriesof Laser Safety documents havebeen approved by ANSI andpublished by Laser Institute ofAmerica (LIA), 5151 Monroe St.,Toledo, OH 43623. These areZ 136.2 “for the safe use of opticalfibers communication systemutilizing laser diodes and LEDsources” and Z136.3 “for safe useof lasers in health care facilities.”The MPL in these documents isfrom Z136.1.


News and NotesContinued

New European Approach toStandardsThe NBS (?) has issued a docu-ment entitled “A Summary of theNew European CommunityApproach to Standards.” Thispublication (NBS 88-3793-1,issued August 1988) summarizesthe IEC plans to achieve an“international market” and thestandard related implementationon U.S. exporters.

IEEE-25 YearsA special issue of IEEE Spectrum(Vol. 25, No. 11) highlights the25 years of publication of theSpectrum, starting January 1964.This issue, rather than emphasiz-ing the history and origin of thepublication, looks at the eventsand engineers in this time period.If you are not an IEEE member,borrow a copy. You will find itinteresting and informative.Presently, the IEEE has 35 Socie-ties and over 30,000 members.

Fiber OpticsThe topic of fiber optics is chang-ing and growing to coordinate theplanned objectives on a nationaland international basis. There is aFiber Optics Coordination Com-mittee (FOCC) under ANSI. AllU.S. organizations that have the

concern or responsibility of devel-oping standards on fiber optics aremembers of the FOCC. The IEEEis represented by Mr. Rautio,Chairman of IEEE StandardsCoordinating Committee 26,Photonics.

Quick Connect TerminalGround ConnectionsCBEMA has written a request toUL with proposals to permit theuse of quick disconnect terminalsfor ground connections. A meetingbetween UL and interestedCBEMA members is to be sched-uled to discuss the applicability ofthis topic.

Product Safety Signs and LabelsAn ANSI draft document Z535.4(first edition, February 1988) esta-blishes design guidelines for safetysigns and labels as applicable to aproduct. This work is part of theZ535 series for documents on“Safety Signs and Colors.” Othersin the series are Z535.1, “SafetyColor Code,” Z535.2, “Environ-mental and Facility Safety Signs,”and Z535.3, “Criteria for SafetySymbols.” This document hasdifferent requirements from thosein IEC 950.

Canadian Radio InterferenceRegulationsThe Canada Gazette, Part II, datedSeptember 28, 1988, has amend-ments to the Radio InterferenceRegulations C.R.C.

Canadian Standards Position onSurface Mounted ComponentsFrom CSA, the following positionstatement was recently issued toone of our readers: “The follow-ing guidelines have been given toCSA Engineers in the InformationProcessing and Business Equip-ment Group. These guidelinesapply only to primary circuits andhigh voltage secondary circuitswhere failure of the solder mount-ing could be expected to cause ahazard:

Surface Mount Components:When used, surface mountedcomponents shall require anadhesive (epoxy type) whichwithstands wave soldering to holdthe component in place. The ad-hesive should be suitable for hightemperatures present during thewave soldering and should notevaporate. In addition, thesecomponents should not come offor dislodge during abnormaltests, especially if they are onlytwo- or four-pin devices.”


In the world of Product Safety andCertification, there are manypitfalls for the unwary. If youhave a problem that seems insol-uble, then it’s time to ask DoctorZ! He has the answers, derivedfrom his many years of trainingand experience in the Science ofProduct Safetiology. Pitfalls holdno terrors for Dr. Z, since he ison a first name basis with most ofthem. Any resemblance to per-sons, places, products, agencies,or good advice is purely coinci-dental, but don’t let that stop you.Write to Dr. Z today.

Dear Dr. Z,If all this engineering stuff is sogood, why aren’t we doing italready? Could it be we are doingit, only you can’t recognize it????Signed,“Not one of your biggestfans”

Dear Fan,Are you sure this shouldn’t beaddressed to the “TechnicallySpeaking” column, or even aletter to the editor???

Oh well, never one to miss anopportunity to expound, Dr. Zwill hazard a response.

First, Dr. Z may be guilty ofmissing present day safety en-gineering work, Dr. Z would bemore than happy to be set straightin this regard. For the most part,most of the safety engineeringwork appears (from my limited

Ask Doctor Z

view) to be happening in some ofthe IEC Pilot functions, but theytoo in many instances seem to begetting sidetracked.

The standards writing pro-cesses are guided by two majorforces. The first is the consensusrequirement for standards writingthat lets coalition building be amore powerful force than data.The second are certificationprocesses which are outside ofthe standards committee control.In this latter case, there is astrong tendency to “maneuver”the requirements to avoid penal-ties from the certification proc-ess. Hidden agendas thrive underthis environment. Most of theeffort is spent addressing “is-sues” that exist because theoriginal requirement was poorlyresearched and constructed. Apolitically expedient fix issearched for to 1) fix whatever,and 2) create no impact on previ-ously certified products. Thisapproach generally prevents theroot problem from being discov-ered and eliminated. Instead,various patches are applied overtime until no one really knowswhat hazard is addressed by therequirement, or to what degreethe requirement provides protec-tion from the hazard.

There is no doubt that safetystandards are an important part ofour world. So are third partysafety certifications. The number

of product standards and require-ments are increasing, as arecertifications. This great rate ofchange does create problems forus all, and if the system is toreally provide the service itintends (safe products), then moreengineering rigor must be injectedinto the processes. Otherwise wewill find ourselves working harderand harder to meet requirementsthat have less and less to do withreal safety.

A number of organizationsprovide information and servicesrelated to satisfying today’ s re-quirements. The PSTC, ratherthan entering into the existingfray, could make a real contribu-tion toward getting engineeringback into the standards writingprocesses by focusing on hazards,their sources, protective mecha-nisms and limit values. The PSTCcharter and strategy certainlysupport such an approach.

Well, Dr. Z didn’t really an-swer your question, but trusts theresponse provides one possibleexplanation of why safety engi-neering is so hard to find in theelectronic product safety field,and provides an opportunity foryou to participate in constructivechange.

Dr.Z


Santa Clara Valley ChapterBrian Claes opened our last meet-ing in November by introducingthe new Santa Clara officers.

Due to a death in the family, thescheduled speaker, Serge Bousquetof CSA, was not able to make hispresentation. Dave Adams ofHewlett-Packard, with 24-hournotice, volunteered to present aslide and talk show on IEC adop-tion status. According to Dave, by1992, Europe will adopt interna-tional standards which all commonmarket countries will accept. Healso discussed how an IEC stan-dard is adopted vs. an ANSIstandard.

The Santa Clara Valley Chapteris looking for a restaurant near themeeting place to get together forpre-meeting attitude adjustmentand dinner. Please call MikeCampi with your suggestions at(408) 773-0770. Presently, youmay find a few members quaffinga brew at the Togo’s on De AnzaBoulevard before each meeting.

Serge Bousquet of CSA will bethe guest speaker at our nextmeeting, Tuesday, January 24,1989, at 7:00 p.m., at AppleComputer, 20525 Mariani Ave.,Cupenino, on the comer of DeAnza Blvd. (just south of Highway280). Serge will discuss severaltopics relating to CSA activitiesand standards (including discussionof CSA developing a 950 basedstandard) and, of course, will beavailable for questions.

Area Activity Reports

Questions regarding the SantaClara Valley Chapter may beaddressed to Mike Campi at (408)773-0770.

Southern California ChapterMinutes for the meeting of Tues-day, December 6, 1988.

At the last meeting of the South-ern California Chapter, Mr. LarryTodd, Division Manager of ETL,gave a slide show and presentationon ETL’s services which areavailable as an alternative to ULservices. Following this presenta-tion, the UL requirements forconductive coatings of plasticswere discussed.

Tom Radley explained how thestandard J type thermocouples canlead to large temperature errorswhen used on switching magnetics.Type T should be used instead toavoid iron as a thermocoupleelement.

A CSA bulletin 1402C on powersupplies and a September 15, 1988bulletin on IEC 950 testing werepassed out. Problems in using theRecognized Component Directoryto identify manufacturer’s identifi-cation were discussed. One idea forimprovement was to include thefile number for nonalphabeticalsections of the directory by manu-facturer’s name.

Canada now has markingrequirements similar to the USAFCC requirements. Equipmentimported into Canada after January31, 1989, must comply and be

labeled. The Canada Gazette, in itsSeptember 28, 1988 issue, pub-lished these requirements. Forfurther information contact: Cana-dian Department of Communica-tions, Garth Roberts, Director,EMC Analysis and ConsultationEngineering Programs Branch, 300Slater Street, Ottawa, Ontario K1A0C8, phone (613) 990-4716.

A draft checklist in use atTUV-R forEN60950 was passedout. TUV-R would appreciate com-ments sent to their San Ramonoffice. TUV-R might consideropening a small Orange Countyoffice if it would be used enough.Differences between TUV - R,TUV-B and TUV-E were dis-cussed.

For further information aboutSouthern California’s chapteractivities, contact Mr. Paul Her-rick, Gradco Systems, (714) 7791223, fax (714) 768-6939.

The next meeting of the South-ern California Chapter will be heldFebruary 7, 1989, at MAl BasicFour, Inc., 14101 Myford Rd.,Tustin, at 6:00 p.m. The speaker forthe evening will be Serge Bousquetof the Canadian Standards Asso-ciation. Serge will speak on thesubject of “Harmonization of CSA22.2 No. 220 with IEC 950.” TheMarch meeting will be held onTuesday, March 7, 1989. Thespeaker for the March meeting hasnot yet been determined.


Pacific Northwest ChapterDue to the difficulty of gettingmembers to commute from Seattleto Portland, and vice versa, findingmultiple speakers with the sameschedule, and finding suitabledining facilities, the officers havedecided to change the way we holdmeetings entirely.

From now on the NorthwestChapter will be split into two areaswith consecutive meetings held inPortland and in Seattle. The twoconsecutive meetings will be ident-ical, as will the speaker and thetime of day. Instead of quarterly,four-hour meetings with multiplespeakers, we will have monthly,one-hour meetings with one spea-ker. For the Portland area meet-ings, Pete Perkins has volunteeredthe Technical Center auditorium inBeaverton. For the Seattle areameetings, Walt Hart has volun-teered their auditorium in Everett.

The meetings for this quarter areas follows:• “Electric Shock,” Rich Nute

February 21, 1989, 7:00 p.m.Tektronix

• “Electric Shock,” Rich NuteFebruary 22, 1989, 7:00 p.m.John Fluke

• “UL in Camas,” Gene BockmierMarch 21, 1989, 6:00 p.m.*Tektronix

• “UL in Camas,” Gene BockmierMarch 22, 1989, 6:00 p.m.*John Fluke

• tbdApril 18, 1989, 6:00 p.m.*Tektronix

• tbdApril 19, 1989, 6:00 p.m.*John Fluke

• tbdMay 16, 1989, 6:00 p.m *Tektronix

• tbdMay 17, 1989, 6:00*John Fluke

* The time for the meetings maymoved to 6:00 p.m., dependingon a discussion we will have inour first meeting. A map will besent out in a separate mailing forthe Northwest Chapter members.

Central Texas Section ChapterMr. George Jurasich, a SeniorProduct Safety Engineer at TUVRheinland of N.A., Inc., is head-ing up a new chapter in Austin,Texas. The fIrst meeting of thechapter is scheduled for March23, 1989, at 10:00 a.m. at SirloinStockade Restaurant, 8820 Re-search Blvd., Austin, Texas. Therestaurant phone number is (512)453-1075. George reports that thefirst meeting will cover productchanges and their impact forproducts subject to compliancewith IEC 950. Questions about themeeting may be addressed toGeorge Jurasich at TUV Rhein-land, (512) 343-6231.

Northeast ChapterThe last meeting of the NortheastChapter was held December 14,1988, at DS&G. Frank McGowanfrom Factory Mutual spoke on“Intrinsic Safety.” The next meet-ing will be held on January 25,1989, again at DS&G. Bob Wersanfrom Panel Components will speakon the IEC Standard 320. JimNorgaard reports that the Februarymeeting has also been planned,with a speaker from CSA reportingon the status of power supplies atCSA. Reference will be made toCSA Bulletins 1402, versions A, B& c. The Northeast Chapter cur-rently has approximately 216 ontheir mailing list and is alwayslooking for more individuals inter-ested in product safety. Questionsabout the chapter may be addressedto Jim Norgaard at DS&G, (508)263- 2662.

Chicago ChapterThe Chicago chapter of the ProductSafety Technical Committee ishappy to announce its first meeting.The meeting is scheduled forMarch 7, 1989, at 7:00 p.m. at thefollowing address: MitsubishiElectric Sales America, Inc., 800Biermann Court, Mt. Prospect, IL60056, contact: John Allen(312) 699-4414. Mr. Stanley Savic,Director of Product Evaluation forZenith Radio Corporation, will betheir guest speaker. Mr. Savic willspeak on Product Liability -- TheOther Side of Quality.

Area Activity ReportsContinued


The following article was pub-lished in the June 1988 edition ofthe Quality Progress Magazineand is reprinted here with permis-sion of the author. In the article,Mr. Rose contrasts, as a safetyengineer, the broad concepts ofquality with the specific responsi-bilities of safety.

Quality is not equivalent to safety.Even a common discipline such asreliability is quite differ-rent inconcept from safety. Some design-ers and product managers havemistakenly thought, “To ensuresafety, we must build more relia-bility into our product.” Thissimply is not true, although thereis a partial, nonlinear correlationbetween quality and safety.

Quality assurance is concernedwith reducing or eliminatingproduct failures. Thus, qualityassurance is concerned, for ex-ample, with the failure of compo-nents within products and withbugs in software programs. QA isconcerned with a design’s successor failure in meeting the functionalspecification for the product. QAis also concerned with ensuringproduct design engineering so thata quality product is created.Whether or not a person sub-scribes to the philosophy of zerodefects, if zero failures could beachieved for a specific product,then the QA objectives would bemet.

Quality vs. Safety

Product safety is concernedwith those failures that result inhazardous situations. Not everyproduct failure will result in ahazardous condition. Manyproduct failures are customernuisances, but will not cause anelectrical shock or burn down ahouse. The program bugs that putsoftware into a continuous loopmay cause frustration and anger,but they are not product safetyconcerns. The scope of qualityassurance is broader than thescope of product safety in thatsafety is concerned only withfailures that result in the risk of ahazard.

Further, product safety is icon-cerned with the effects of faultsand failures that result in settingup a potential hazard. This con-cern is one step removed from theactual failure itself. The goal ofproduct safety is to anticipateevery possible fault condition.During a product evaluation, faultconditions are introduced one at atime to determine their effect.This is called fault effect analysis.The second pan of this goal is tostudy the effect of the fault condi-tion to determine what will renderthe effect harmless. Quality assur-ance is concerned with failureanalysis and fault tree analysis,while product safety is concernedwith fault effect analysis.

The Three Basic HazardsWhen a failure or fault conditionwould result in the risk of a hazard,then product safety engineering isconcerned with eliminating orreducing the potential risk. Thereare three basic hazards with whichsafety is concerned: property lossrisks, such as fire loss, businessloss interruption, and corruption ofessential data; personal accidentinjury and personal health injury,such as electrical shock and expo-sure to x-radiation; and environ-mental degradation, such as radiofrequency interference or theresults of improper disposal ofPCBs from capacitors.

Product safety eliminates theeffect of a failure or fault conditionbut does not eliminate the failureitself, because the failure conditionis assumed to occur. For example,fuse protection is placed in house-hold wiring because it is assumed ashort circuit, or an overload situ-ation such as a motor bearingwearing out, may occur. Under thefault condition, the disastrouseffect of the failure is eliminatedby the blowing of a fuse. The samesituation is true for all types ofproducts.

Some safety approval agenciesblur the distinction by misapplyingthe definition of fail-safe. Interlockswitches are a case in point. Theinternational test agencies state thatwhen an interlock switch for safetypurposes fails, it must fail safely in

by Manning I. Rose


the off position. The conventionalsnap switch for UnderwritersLaboratories is tested for 50 over-load cycles, 4,000 normal loadcycles, and 6,000 no-load cycles.The interlock switch is tested for100,000 cycles in contrast to theapproximate 10,000 cycles for asnap switch. In other words, theinterlock switch is assumed tonever fail because of high reliabil-ity and as being tantamount tofail-safe.

This distinction between do-mestic and international fail-safedefinitions has led to pan of theconfusion surrounding the differ-ences between product safety andquality assurance. It is true that ifthere were no product faults orfailures, there would be no needto consider the effect of faultconditions. With a completelyreliable product, there is no needfor product safety in the design,except for perhaps the humaninterface points where users canoverride the reliability.

Repeal Murphy’s LawOne motto I have used to illustratethis point is “Repeal Murphy’sLaw.” Of course, Murphy’s Lawcan never be repealed. But likemany legislative statutes,Murphy’s Law can be renderedharmless by removing the teeth ofthe effect of the law. The fault-free product similar to zerodefects is a design goal, but nevercan be realized. Thus, the only

Quality vs. SafetyContinued

real solution is to render Murphy’sLaw completely harmless byeliminating any harmful effects offault conditions.

Another point of confusionbetween quality assurance andproduct safety is the litigationissue surrounding products andproduct failure. Litigants can suemanufacturers on the basis ofproduct warranties and also on thebasis of injury. When personalinjury, property loss, or environ-mental degradation is the issue,then the lawsuit is on the basis ofdesign defect, improper design, ora manufacturing defect. Themanufacturing defect that resultsin the setting up of a hazardouscondition may be the result ofimproper quality control proce-dures or an improper designcontrol procedure for productsafety. The cause is of no concernto the litigant, but the manufac-turer may wish to identify thecause to correct it.

Two Ways to View the SameSituationStill another point of confusionbetween product safety and qualityassurance is that both disciplinesdiscuss the same materials withina product, but to a different end.QA assembles voluminous statis-tics on the failure rate of insulationsystems and insulating materials.Product safety, on the other hand,discusses mutually exclusivefailures of insulation systems in a

double protection system such asdouble insulation. Product safety isnot concerned with the rate offailure and is only slightly inter-ested in the probability of failure.The concern is for the likelihood oftwo mutually independent failuresoccurring in such a manner as tocreate a hazardous condition.Product safety, therefore, is con-cerned with providing backupsystems, like the second level ofinsulation, that guarantee against afault condition.

Another blurring of the distinc-tions between quality assuranceand product safety results from themanagement evolution to considerever-widening scopes in productsafety and quality. The scopes arewidening from the view of atechnology explosion and from theview of considering new dimen-sions over the traditional field ofquality control. In some majororganizations, the quality assur-ance management spans the de-signs within the engineeringdepartment during the productevaluation phase to determine ifthe new design fulfills the designspecifications and objectives. Inthis case, quality assurance isconcerned with product safetycompliance with the product safetyspecifications as set forth by theproduct safety professional. Thus,QA is concerned with productfailures to meet the safety specifi-cations. Even with this very broad

Continued


management scope on the partof QA, product safety is still con-cerned with the effect of theseproduct failures. While there arediscrete distinctions betweenquality assurance and productsafety, there is nonetheless theneed for very close cooperationbetween the disciplines withrespect to management andproduct development.

The term product evaluation isvery broad and could encompassaspects from both product safetyand quality assurance. Productsafety is concerned with safetycompliance testing and fault effectanalysis. QA is also concernedwith compliance testing to prod-uct specifications and failureanalysis. Hence the term productevaluation tends to fade specificdistinctions between QA andsafety. Similarly, production linetesting, the traditional domain ofQA, is an area where the distinc-tion overlaps. Here, QA tests forthe functionality of the productsafety systems, grounding, insula-tion resistance to leakage current,and dielectric strength. QA testingto determine whether a productfunctions as planned is different

from tests for product safetydeterminations in compliance withsafety principles.

Faults and FailuresThe distinctions between qualityassurance and product safety areclearly discerned when one exam-ines the relationship of faults andfailures. Product safety deals withthe person-product, property-product, and environment-productinterfaces in systems relationships.It is impossible to discuss productsafety without the relationshipbeing implied and understood. Theterm safety denotes that the prod-uct will not represent the risk of ahazard to the other party in the re-lationship. Quality assurance doesnot carry this connotation. WhileQA compares a component or pro-duct with specifications, standards,and implied functional require-ments, there is no implied interac-tive relationship between the pro-duct and the comparative partyother than the quality assessment.

In general, quality assuranceis involved in failures, failureanalysis, statistical rates of failure,and manufacturing control proce-dures, whether or not these involve

hazards or possess an impliedinterface relationship. Productsafety deals with effects of haz-ard-producing failures, risk-producing failures, fault effectanalysis, and design-engineeringcontrol, with the implied andunderstood knowledge of aninteractive relationship. QAreduces failures; product safetyreduces risks of hazards.

Manning I. Rose, MA, PE, CPSM,is a product safety consultant andpresident of MIRA Corporation.He is an engineering professor,professional engineer, productsafety consultant to NCR Corpo-ration, and the author of manyproduct safety articles in majorengineering and quality publica-tions. Mr. Rose is an inventor withten patents and InternationalChairman of the IEC Committeethat published IEC 380. Mr. Rosehas been active continuously inproduct safety engineering for 28years. He conducts safety semi-nars and may be reached at (513)434-7127; Mira Corporation,2301 Glenheath Dr., Kettering,OH 45440-1905

Quality vs. SafetyContinued


As promised in last month’s issue, some introductions are in order for the staff serving you .throughthe Product Safety Newsletter.

The above individuals are essential to the successful publication of each edition. May I suggest that if youenjoy their efforts, you write them a note, by way of the newsletter, telling them how much you appreciatetheir hard work? As you can see, there are some who are doing double duty. Future success of the newsletterdepends a great deal on you. Anyone in any location in the country could be a great help with managingeither subscriptions or contributions. Perhaps there are other ways that you would like to help. Please let meknow. When several each take a small part, no one person is overloaded and everyone can have the satisfac-tion of participating in the beginning phases of an exciting, new international publication.

We have sent letters to those of you who have expressed interest in writing for the newsletter, explaininghow to best prepare and submit your articles. Allow me to explain the process to those of you who have notcontacted us. For 1989, articles for each edition are due by the first Friday of the month for the two-monthperiod covered by the issue (Le., articles for the March/April edition are due the fIrst Friday of March).Articles should address some aspect of product safety and be limited in length to 2000 words. The newsletterstaff reserves the right to edit all articles for readability, length, and grammar. We are working with the IEEEand our National officers to develop a policy on advertisements and/or contributors.

Should you have any questions or suggestions on how to improve the newsletter, please give me a call at(408) 748-2102.

Roger VolgstadtEditor

Editorial

• Jane BennerNewsletter preparation

• Dave Edmunds“News and Notes” Editor

• Jodi ElginProduction Editor

• John McBainAssistant Editor

• John McBain (acting)Subscriptions Manager

• Rich NuteAuthor, “Technically Speaking”

• Richard PescatoreAuthor, “Chairman’s Message”

• John ReynoldsEditor, Technical Articles

• Annie ValvaDesktop Publishing

• Roger Volgstadt (acting)Contributions Manager

• Roger VolgstadtManaging Editor

• Dr. ZAuthor, “Ask Doctor Z”


As you probably know, 1992 in Europe means one thing: deregulation and the relaxation of trade barriersbetween European countries. The following flowchart shows three possible processes for investigatingsafety of products in Europe. Unfortunately, even if it is completely accurate now, it may not be correct inthe future. Path C has a reasonable chance of becoming not just unacceptable to customers, but actually notpermitted (illegal!). Path B is not especially favored by third party test houses, which have considerableinfluence in Europe. Stay tuned, folks! The year 1992 should be a big one for product safety.

Please keep in mind that this model is only an attempt to clarify what happens in the real world. Under-lying assumptions and oversimplification may erode its utility. So, any comments on what is really goingon??? Let’s see some letters!

EUROPEAN CONFORMITY ASSURANCE SCHEME - 1992

A Summary of European Regulatory Compliance for 1992John McBain



c/o Tandem Computers Incorporated2550 Walsh AvenueSanta Clara, Ca 95051Attn: Roger Volgstadt

Tuesday, March 7Chicago ChapterSubject: Product Liability---

The Other Side of QualitySpeaker: Stanley SavicTime: 7:00 p.m.Location: Mitsubishi

800 Biermann CourtMt. Prospect, IL

Contact: John Allen(312) 699-4414

Tuesday, March 7Southern California ChapterSpeaker: TBATime: 6:00 p.m.Location: MAl Basic Four

14101 Myford Rd.Tustin, CA

Contact: Paul Herrick(714) 779-1223

Tuesday, March 21Pacific Northwest ChapterSubject: UL in CamasSpeaker: Gene BockmierTime: 6:00 p.m. (tentative)Locations: Tektronix

John Fluke (March 22)Contact: AI Van Houd1

(206) 882-3700Wednesday, March 22Northeast ChapterSubject: CSA UpdateSpeaker: TBATime: 7:00 p.m.Location: Sheraton Boxborough Intersec-

tion of Rts 495/111 Boxborough,Mass

Contact: Jim Norgaard(508) 263-2662

Thursday, March 23Central Texas ChapterTime: 10:00 a.m.Location: Sirloin Stockade Restaurant

8820 Research Blvd, Austin, TX(512) 453-1075

Contact: George Jurasich(512) 343-6231

CalendarThe Product Safety Technical Committee of the IEEE EMC Society

Tuesday, March 28Santa Clara Valley ChapterSubject: Evaluation and Testing of

Power SuppliesSpeaker: Jose BravoTime: 7:00 p.m.Location: Apple Computer

20525 Mariani Ave. Cupertino.CA

Contact: Mike Campi(408) 773-0770

Tuesday, March 28Santa Clara Valley ChapterSubject: Temperature Measurements in

High RF EnvironmentSpeaker: Paul LantzTime: 7:00 p.m.Location: Apple Computer

20525 Mariani Ave. Cupertino.CA

Contact: Mike Campi(408) 773-0770

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