Category Archives: Uncategorized

Inconsistencies in ISO 13849–1:2006

Posted by on November 10, 2011 1 comment
This entry is part 7 of 8 in the series Circuit Architectures Explored

I’ve writ­ten quite a bit recently on the topic of cir­cuit archi­tec­tures under ISO 13849–1, and one of my read­ers noticed an incon­sis­tency between the text of the stan­dard and Figure 5, the dia­gram that shows how the cat­e­gories can span one or more Performance Levels.

ISO 13849-1 Figure 5

ISO 13849–1, Figure 5: Relationship between Categories, DC, MTTFd and PL

If you look at Category 2 in Figure 5, you will notice that there are TWO bands, one for DCavg LOW and one for DCavg MED. However, read­ing the text of the def­i­n­i­tion for Category 2 gives (§6.2.5):

The diag­nos­tic cov­er­age (DCavg) of the total SRP/​CS includ­ing fault-​​detection shall be low.

This leaves some con­fu­sion, because it appears from the dia­gram that there are two options for this archi­tec­ture. This is backed up by the data in Annex K that under­lies the diagram.

The same con­fu­sion exists in the text describ­ing Category 3, with Figure 5 show­ing two bands, one for DCavg LOW and one for DCavg MED.

I con­tacted the ISO TC199 Secretariat, the peo­ple respon­si­ble for the con­tent of ISO 13849–1, and pointed out this appar­ent con­flict. They responded that they would pass the com­ment on to the TC for res­o­lu­tion, and would con­tact me if they needed addi­tional infor­ma­tion. As of this writ­ing, I have not heard more.

So what should you do if you are try­ing to design to this stan­dard? My advice is to fol­low Figure 5. If you can achieve a DCavg MED in your design, it is com­pletely rea­son­able to claim a higher PL. Refer to the data in Annex K to see where your design falls once you have com­pleted the MTTFd calculations.

Thanks to Richard Harris and Douglas Florence, both mem­bers of the ISO 13849 and IEC 62061 Group on LinkedIn for bring­ing this to my attention!

If you are inter­ested in con­tact­ing the TC199 Secretariat, you can email the Secretary, Mr. Stephen Kennedy. More details on ISO TC199 can be found on the Technical Committee page on the ISO web Site.

Bye, Steve. Thanks for everything!

Posted by on October 6, 2011 3 comments

Today marks a turn­ing point for me. With the loss of Steve Jobs, the world is a lesser place. His bril­liance, vision and charisma changed the world for the bet­ter in so many ways.

Bye SteveAs any­one who knows me well will tell you, I am a pas­sion­ate Mac user. I became a believer in 1991 when my then-​​girlfriend intro­duced me to her SE-​​30, “Peanut”, but my his­tory with Apple goes back all the way to 1980. As a Grade 10 stu­dent, I landed a job sell­ing Apple com­put­ers. We were sell­ing Apple II’s, II+‘s, IIe’s and III’s in those days. The Apple II was the first game changer from Apple, deliv­ered in the days when com­put­ers were behe­moths owned by cor­po­ra­tions, and the University of Waterloo’s Red Room was the heart of their com­puter sci­ence pro­gram. I remem­ber the launch of the Lisa, and I remem­ber my first expe­ri­ence of a graph­i­cal UI on the Lisa we had in the showroom.

I became an EvangeLista in the ’90’s, sub­scrib­ing to the Mac EvangeList pub­lished by Guy Kawasaki. Armed with GK’s facts, I went armed into bat­tle with my PC lov­ing col­leagues. I watched in hor­ror as Sculley ousted Steve from Apple, and the com­pany entered a period of medi­oc­rity that nearly ended it when Gil Amelio took charge and in a stroke of vision­less lead­er­ship insisted on build­ing the same crappy beige boxes that every­one else was building.

My evan­ge­lism never slack­ened, despite these set­backs, despite the crit­i­cism and doom­say­ing of friends, fam­ily and col­leagues. I con­tin­ued to pick fights with PC users who just didn’t, and couldn’t, “get it”.

My heart soared when Steve came back to Apple, and the launch of the first iMacs in Bondi Blue changed the world. It was the begin­ning of the rev­o­lu­tion I always knew would come. My Bondi Blue Rev B iMac still works, and has a safe place in my house, as a reminder of what change can look like.

As I sit writ­ing this on my 27″ I5 iMac, I am in awe of what great lead­er­ship can do. To say that I am inspired by Steve Jobs leaves it a lit­tle short.

So this year I’ll add October the 5th to my Mac cal­en­dar, next to January 24th, 1985, as a key date in my cal­en­dar. I’ll remem­ber and be inspired by Steve’s words and actions as a great leader, a great busi­ness­man, and a great per­son. I’ll try to make my life a lit­tle sim­pler and a lit­tle clearer, fol­low­ing his lead, and I’ll say “Thanks for every­thing, Steve. We’ll miss you!”.

–

Doug Nix — Macintosh Evangelista
dnix@mac.com

CSA Z462 — Workplace Electrical Safety Public Review

Posted by on April 1, 2011 1 comment

CSA Z462 — Workplace Electrical Safety is now avail­able for pub­lic review on the CSA web site. This stan­dard is the Canadian imple­men­ta­tion of NFPA 70E and IEEE P1584, cov­er­ing elec­tro­cu­tion and arc-​​flash haz­ards in the workplace.

Public Review Draft of Z462-​​12

Because of the impor­tance of the Z462 Standard to the elec­tri­cal sec­tor, CSA staff have decided to set up the draft on the new On-​​line Public Review System. This sys­tem is inte­grated with sev­eral on-​​line social net­works and has been made avail­able to a wide inter­na­tional audi­ence. Automatic noti­fi­ca­tion will go out to all peo­ple and orga­ni­za­tions that have expressed inter­est in CSA’s elec­tri­cal stan­dards (thou­sands of stakeholders).

There are two major dif­fer­ences in the way this new on-​​line review sys­tem works:

1.       The reviewer must first reg­is­ter with the sys­tem to gain access to the draft stan­dards (name, affil­i­a­tion, coun­try, and e-​​mail address).

- the reviewer must have a valid e-​​mail address (identity)

2.       The doc­u­ment is only avail­able on-​​line (no down­load) and it is review­able only in pieces for com­ment­ing purposes.

- sim­i­lar to the mem­bers’ bal­lot com­ments, the sys­tem auto­mat­i­cally col­lects and sorts the com­ments by clause number.

Note: the new review page is also acces­si­ble via a link located at the top of the old Review Page (https://​review​.csa​.ca/​o​p​r​/​o​p​r​_​l​i​s​t​.​asp) – iden­ti­fied as “New: …Electrical pub­lic review drafts”.

For more infor­ma­tion on this stan­dard, please con­tact the CSA Project Manager, Mr. Dave Shanahan, dave.shanahan@csa.ca, or call him at 1−800−463−6727.

All original content on these pages is fingerprinted and certified by Digiprove
Performance Optimization WordPress Plugins by W3 EDGE