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'Reliability thinking and risk assesment'
1997\08\11@123630 by Mike

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At 05:54 PM 8/11/97 +0930, MikeS <spam_OUTmikesmith_ozTakeThisOuTspamrelaymail.net> wrote:

>But do you turn off the following when leaving your house - VCR, clock
>radio, TV, microwave, hifi, fridge, freezer(ouch)?  These all operate whilst
>in 'non-attended' mode.  Some would be a PITA to turn off every time you
>left for a short duration - some not really possible (deep freeze)  They all
>pose a risk though.

Yes. I turn off everything that has a switchmode supply in it which is
not a brand name product by the biggest companies. So therefore, I use
smoke detectors with interlock to the mains power so it turns off the
power points within 10 seconds of being tripped (AND still leaves the
light circuit active so I can see at night in case of alarm).

I leave the clock radio on since it has one of those very nice conventional
transformers AND a PTC in series with it. And if I go away for more than
2 days - I turn off the freezer - since I wouldn't risk the bacterial
contamination in case the utility turned off the supply while I was gone
and just happened to turn it back on a couple of hours before I got back,
I know of one person who got sick for this very reason !

Risk assesment is an area which I have some philosophical interest both
in terms of hardware design and software methodology.

I am of the opinion that the 1 in 10 million is a bit optimistic when it
comes to PC switchmode power supplies - UNLESS they are from the top brand
name suppliers like HP, COMPAQ etc - then you *might* be close.

In Australia we get lots of PC power supplies made by Chinese sweat shops
and I've seen how they treat integrated circuits and switchmode transistors
in respect of static - I am NOT impressed by what I have seen at ALL !

So when I have the opportunity to reduce risk - I do. I am not the sort
of person who adds to risk or waves it away by saying "well the chances of
being knocked over by a car are .... so why should I turn of my power
supply cause I 'think' its a 1 in 10 million shot..." etc - This is very
bad logic not congruent with engineering intellectualism leading to well
designed and safety concious products.

Faith and electronics reliability (to me) are mutually exclusive concepts.

A faithful switchmode power supply is 'almost' an oxymoron !

rdgs

mike

PS: Insurance is NEVER a substitute for prevention, tell that to your
children if/when they lose their favourite toys or photographs etc.


Some say there is no magic but, all things begin with thought then it becomes
academic, then some poor slob works out a practical way to implement all that
theory, this is called Engineering - for most people another form of magic.
                                                                      Massen

1997\08\11@132741 by John Shreffler

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part 0 910 bytes
-----Original Message-----
From:   Mike [SMTP:.....erazmusKILLspamspam@spam@WANTREE.COM.AU]
Sent:   Monday, August 11, 1997 12:37 PM
To:     PICLISTspamKILLspamMITVMA.MIT.EDU
Subject:        Reliability thinking and risk assesment

At 05:54 PM 8/11/97 +0930, MikeS <.....mikesmith_ozKILLspamspam.....relaymail.net> wrote:

[snip]
. And if I go away for more than
2 days - I turn off the freezer - since I wouldn't risk the bacterial
contamination in case the utility turned off the supply while I was gone
and just happened to turn it back on a couple of hours before I got back,
I know of one person who got sick for this very reason !

Seems like a lot of trouble to transfer all your frozen goods to
the neighbor's freezer, just because you are going away for
a few days.  Here's an old Indian trick I use.  I have a baggie
with a few ice cubes in it.  If it got warm enough to threaten
the food, the baggie would be filled with a misshapen blob
of ice.

1997\08\11@155013 by Mike

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At 01:08 PM 8/11/97 -0400, you wrote:

>
>[snip]
>. And if I go away for more than
>2 days - I turn off the freezer - since I wouldn't risk the bacterial
>contamination in case the utility turned off the supply while I was gone
>and just happened to turn it back on a couple of hours before I got back,
>I know of one person who got sick for this very reason !
>
>Seems like a lot of trouble to transfer all your frozen goods to
>the neighbor's freezer, just because you are going away for
>a few days.  Here's an old Indian trick I use.  I have a baggie
>with a few ice cubes in it.  If it got warm enough to threaten
>the food, the baggie would be filled with a misshapen blob
>of ice.

No. I don't keep a lot of frozen food, only fish fingers and kangaroo
meat. I'm not one of those people that use huge freezers. Where possible I
eat fresh food each and every day. The freezer is very rarely used.

Anyway - its a nice idea about the bag of ice cubes, simple but effective
- I'll remember that and reduce my risk even further ;)

rgds

mike
Perth, Western Australia

1997\08\11@194349 by Glenn Johansson

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part 0 615 bytes
Kangaroo meat? Fish fingers? Huge freezers?

This is so far off topic, that I am wondering if the author is harrassing us with his unscientific stupidities on purpose...

Glenn
Sweden
PS. The formula is THREAT = RISK * HARM (HARM is the harm which is done if the accident happens, RISK is the probablility that it happens (a value between 0.000 and 1.000), and THREAT is a combination of the two, indicating how far one should go to prevent a possible accident. Disassembling ones clock radio to find out whether it's built in a way that could cause fires, as this man obviously has done, is just not worthwhile.)

1997\08\11@204710 by William Chops Westfield

face picon face
FWIW, we're not talking about how many PC power supplies fail, but how many
fail in such a way as to burst into flames and set fire to the surroundings,
which puts the probability figure way down.

In a company with several thousand PCs, many of which are no-name clones and
few of which are ever turned off (many sitting in labs unattended and unused
for weeks or months at a timer), I don't think we've ever had a fire...

BillW

1997\08\11@231659 by Mike Smith

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---Original Message-----
From: Mike <EraseMEerazmusspam_OUTspamTakeThisOuTWANTREE.COM.AU>
To: PICLISTspamspam_OUTMITVMA.MIT.EDU <@spam@PICLISTKILLspamspamMITVMA.MIT.EDU>
Date: Tuesday, 12 August 1997 02:07
Subject: Reliability thinking and risk assesment



>At 05:54 PM 8/11/97 +0930, MikeS <KILLspammikesmith_ozKILLspamspamrelaymail.net> wrote:
>
>>But do you turn off the following when leaving your house - VCR, clock
>>radio, TV, microwave, hifi, fridge, freezer(ouch)?  These all operate
whilst
>>in 'non-attended' mode.  Some would be a PITA to turn off every time you
>>left for a short duration - some not really possible (deep freeze)  They
all
>>pose a risk though.
>
>Yes. I turn off everything that has a switchmode supply in it which is
>not a brand name product by the biggest companies. So therefore, I use

Do you pay attention to things like UL ratings?

>smoke detectors with interlock to the mains power so it turns off the
>power points within 10 seconds of being tripped (AND still leaves the
>light circuit active so I can see at night in case of alarm).

Nice idea that.  Unfortunately, in some cases, by the time a sufficient
volume of smoke makes its way to the smoke sensor, its a little late -
you've got a self-sustaining fire.  But it would stop electricity from
becoming involved further.

Its a good argument for metal enclosures for PC's too.  That would reduce
risk, compared to the nice, contoured ones many (incl Compaq)  are producing
these days.

>
>I leave the clock radio on since it has one of those very nice conventional
>transformers AND a PTC in series with it. And if I go away for more than
>2 days - I turn off the freezer - since I wouldn't risk the bacterial
>contamination in case the utility turned off the supply while I was gone
>and just happened to turn it back on a couple of hours before I got back,
>I know of one person who got sick for this very reason !

Um, not nice.  Be easy to make a cheap PIC cct that monitored freezer temp,
and wrote info in NV memory to indicate dangerous temperatures.  Good app
for the 8pin device.

{Quote hidden}

But Mike, if they're made in humid conditions, then that implies low static
risk! <g>

>
>Faith and electronics reliability (to me) are mutually exclusive concepts.

Not implying faith, more pragmatism...  You can never reach 100%
reliability - so at what level do you declare a product ready to ship?

>
>A faithful switchmode power supply is 'almost' an oxymoron !
>

Yet you put your faith (sorry, that word again) in linear power supplies?
They use semis too, and a fault in them could cause the transformer to cook
off - and cause a fire...  PTC's only work up to a certain (power) level.
And not all manufacturers fuse them adequately.

MikeS
<RemoveMEmikesmith_ozTakeThisOuTspamrelaymail.net>

1997\08\11@233530 by Mike Smith

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----Original Message-----
From: Mike <spamBeGoneerazmusspamBeGonespamWANTREE.COM.AU>
To: TakeThisOuTPICLISTEraseMEspamspam_OUTMITVMA.MIT.EDU <RemoveMEPICLISTspamTakeThisOuTMITVMA.MIT.EDU>
Date: Tuesday, 12 August 1997 05:22
Subject: Re: Reliability thinking and risk assesment

<snip>

>No. I don't keep a lot of frozen food, only fish fingers and kangaroo
>meat. I'm not one of those people that use huge freezers. Where possible I
>eat fresh food each and every day. The freezer is very rarely used.

Kangaroo is one of the nicest meats around, but few ppl seem to be
interested.  Low fat/cholesterol, too!  One of the better presentations of
it I've tried has been as a schnitzel type dish, prepared by an Argentinian.

Fish fingers though?

MikeS
<mikesmith_ozEraseMEspam.....relaymail.net>

1997\08\11@235536 by Mike Smith

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-----Original Message-----
From: John Shreffler <EraseMEjohnsspamAVENUETECH.COM>
To: RemoveMEPICLISTEraseMEspamEraseMEMITVMA.MIT.EDU <RemoveMEPICLISTspam_OUTspamKILLspamMITVMA.MIT.EDU>
Date: Tuesday, 12 August 1997 03:00
Subject: Re: Reliability thinking and risk assesment



{Quote hidden}

Another great idea down the chute.  (using a PIC!)

MikeS
<mikesmith_ozSTOPspamspamspam_OUTrelaymail.net>

1997\08\12@012821 by Shane Nelson

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<snip>

Thought you all should know:

       I was showing a friend what goes on here
       on the piclist.  Claiming this is the
       "geekiest thing ever," she has started saving
       it as a "shining example" of the extreme
       geekiness that can be achieved with the
       assistance of thousands of
       Programmers In Cooperation.


       ;)


-Shane.

1997\08\12@022300 by tjaart

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Shane Nelson wrote:
>
> <snip>
>
> Thought you all should know:
>
>         I was showing a friend what goes on here
>         on the piclist.  Claiming this is the
>         "geekiest thing ever," she has started saving
>         it as a "shining example" of the extreme
>         geekiness that can be achieved with the
>         assistance of thousands of
>         Programmers In Cooperation.
>
>         ;)

Tha fact that she's only a friend, proves your point ;)

--
Friendly Regards

Tjaart van der Walt
spamBeGonetjaartSTOPspamspamEraseMEwasp.co.za
________________________________________________________
|        WASP International   http://wasp.co.za          |
|   R&D Engineer : GSM peripheral services development   |
|Vehicle tracking | Telemetry systems | GSM data transfer|
|Voice : +27-(0)11-622-8686  |  Fax : +27-(0)11-622-8973 |
|             WGS-84 : 26010.52'S 28006.19'E             |
|________________________________________________________|

1997\08\12@031929 by Pasi T Mustalahti

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On Mon, 11 Aug 1997, Mike wrote:
> At 05:54 PM 8/11/97 +0930, MikeS <KILLspammikesmith_ozspamBeGonespamrelaymail.net> wrote:
> >But do you turn off the following when leaving your house - VCR, clock
> >radio, TV, microwave, hifi, fridge, freezer(ouch)?
>
> I leave the clock radio on since it has one of those very nice conventional
> transformers AND a PTC in series with it.

PTM: It might be better NOT to tell you what my previous clock radio did
and what is left off it. And it had a conventional transformer ;)

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PTM, EraseMEpasi.mustalahtispamEraseMEutu.fi, @spam@ptmusta@spam@spamspam_OUTutu.fi, http://www.utu.fi/~ptmusta
Lab.ins. (mikrotuki) ATK-keskus/Mat.Luon.Tdk                    OH1HEK
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Mail: Turun Yliopisto / Fysla, Vesilinnantie 5, 20014
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1997\08\12@041233 by Mike

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At 05:45 PM 8/11/97 PDT, you wrote:

>In a company with several thousand PCs, many of which are no-name clones and
>few of which are ever turned off (many sitting in labs unattended and unused
>for weeks or months at a timer), I don't think we've ever had a fire...

Great - but, please understand that your sample size is still very low.

rgds

mike
Perth, Western Australia

1997\08\12@043343 by Mike

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At 12:44 AM 8/12/97 +-200, you wrote:

>This is so far off topic, that I am wondering if the author is harrassing
us with his unscientific stupidities on purpose...

YES it is off topic - but the person who made a presumption which is
unscientific has been informed of the circumstances. I think you should
really check the definition for science before you ever consider defaming
someone by suggesting "unscientific stupidities"  this is tantamount to
abusing someone because you think you know better of their circumstances
when you obviously cannot - this suggests considerable inexperience.

>Glenn
>Sweden
>PS. The formula is THREAT = RISK * HARM (HARM is the harm which is done if
the accident happens, RISK is the probablility that it happens (a value
between 0.000 and 1.000), and THREAT is a combination of the two,
indicating how far one should go to prevent a possible accident.
Disassembling ones clock radio to find out whether it's built in a way that
could cause fires, as this man obviously has done, is just not worthwhile.)

This is the most unscientific rubbish I have ever seen and bears no
relationship to reality and shows the most stupid presumption based
on ignorance and willingness to bite into an issue you know nothing
about.

Would you ever quote this formula to the parent of a child killed in
a plane crash - Eh ?

How do you quantify HARM ?

Is it a number, can you put a number to the pain of a burn across your
face for 20 years - who do you think you are ?

How do you determine RISK ?

All you can ever do is concientiously reduce risk by the most reasonable
methods at your disposal at the time.

What is the relevance of THREAT ?

In the context of the clock radio how do you decide from the number you
get from your 'formula' whether you should make a mental note about its
contstruction - as this might be useful when filling in an insurance
application - Eh ?

Its amazing how *stupidly* presumptuous people can be, I must thank you
for your post as you have just given me a series of ideas on what questions
to ask potential employees when it comes to how far they are prepared to
go to design reliable products and prevent injury to customers.

The clock radio in question failed when it fell off the end of
the bed head - I opened it up to show my Son how it worked and to determine
the cause of the failure - it turned out to be a simple solder/pad break
on the transformer, less than 5 minutes with a solering iron had it
fixed and guess what by opening it up I could dismiss the likelihood that
this device could be instrumental in causing a fire.

Mike
Perth, Western Australia

1997\08\12@050119 by Mike

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At 12:46 PM 8/12/97 +0930, you wrote:

>>Yes. I turn off everything that has a switchmode supply in it which is
>>not a brand name product by the biggest companies. So therefore, I use
>
>Do you pay attention to things like UL ratings?

Only when they apply to products from the top brand name companies, I've
seen a manufacturer in Shanghai who churned out these UL labels by the
thousands each day and sold them to anyone !

>Nice idea that.  Unfortunately, in some cases, by the time a sufficient
>volume of smoke makes its way to the smoke sensor, its a little late -
>you've got a self-sustaining fire.  But it would stop electricity from
>becoming involved further.

If I could, I'd use a CO sensor, since the detection of partial combustion
can be much sooner than self sustained combustion and may very well give
more time to have the fire NOT start if the power was removed etc.

>Um, not nice.  Be easy to make a cheap PIC cct that monitored freezer temp,
>and wrote info in NV memory to indicate dangerous temperatures.  Good app
>for the 8pin device.

Someone mentioned a bag of icecubes - now thats a nice simple solution,
well it would turn into a solution if the power went off ;-)

>But Mike, if they're made in humid conditions, then that implies low static
>risk! <g>

Oh yeah - faith again mike - close proximity to plastic bags when
sliding etc is unlikely to be dissipated by high humidity, I recall some
early science experiments where water droplets were charged up etc..

>Not implying faith, more pragmatism...  You can never reach 100%
>reliability - so at what level do you declare a product ready to ship?

This is a good point. If something is going to be used in an unattended
environment then I would have more than one fail safe mechanism, like
a PTC and fuse and regulators with thermal and current shutdown etc

>>A faithful switchmode power supply is 'almost' an oxymoron !

>Yet you put your faith (sorry, that word again) in linear power supplies?

No. Just because I don't like the way many SMPS are made does not imply
I like linears, these also need care in design and construction.

>They use semis too, and a fault in them could cause the transformer to cook
>off - and cause a fire...  PTC's only work up to a certain (power) level.

True - so I get a transformer from a brand name supplier that already
builds the PTC into the transformer - for unattended products, let them
carry the can...

>And not all manufacturers fuse them adequately.

True, so I always design my own for unattended operation. I'm quite happy
to mess around with cheap non brand stuff but never use it for anything
which might end up in a risky scenario or for unattended operation.

Rgds

Mike
Perth, Western Australia

1997\08\12@050328 by Mike

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At 01:07 PM 8/12/97 +0930, you wrote:
>Kangaroo is one of the nicest meats around, but few ppl seem to be
>interested.  Low fat/cholesterol, too!  One of the better presentations of
>it I've tried has been as a schnitzel type dish, prepared by an Argentinian.

Yes - tried it once but couldn't stomach doing it myself, there are so
many Kangaroos around that I'm happy to have  them used as cat food.

>Fish fingers though?

Cheap and quick - thats all...

By the way - Quiz - why does the Australian Coat of Arms have the
Kangarroo and Emu on it ?

Rgds

Mike



Some say there is no magic but, all things begin with thought then it becomes
academic, then some poor slob works out a practical way to implement all that
theory, this is called Engineering - for most people another form of magic.
                                                                      Massen

1997\08\12@082740 by Mike Harrison

picon face
Dear All
I've left the copied body in for a reason.. Mike (perth) I believe you are
quite wrong to splash so much bile across Glenns' comments. The purpose of
the threat formula is to aid in project and product planning in terms of
risk to the project and the likely cost of alternative/extra action required
to rectify in terms of time and capital. In such a context the formula is
very valuable if simplistic. A good manager will have an idea of the
relative weights of the RISK factor and possibly a good idea of the Harm
factor but it is still imprecise and subjective and is thus not a rigorous
rule. Your example of a plane crash is facile in this context.
Please feel free to pick up any bok on project management, particularly
software and teher it is in all its glory. (..or infamy) So in a way this is
directly related to PIC projects
{Quote hidden}

Sorry if I wasted your bandwidth, I felt it was important.
Mike
***************************************************************************
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1997\08\12@085254 by Russell McMahon

picon face
---------
> From: Shane Nelson <TakeThisOuTi.....spamTakeThisOuTCHEETAH.SPOTS.AB.CA>
> Thought you all should know:
>
>         I was showing a friend what goes on here
>         on the piclist.  Claiming this is the
>         "geekiest thing ever," she has started saving
>         it as a "shining example" of the extreme
>         geekiness that can be achieved with the
>         assistance of thousands of
>         Programmers In Cooperation.
>
Well then, its nice to think that I originated this thread :-)
(even if it was on a different topic originally!)

Does this make me a super geek?

       Russell

1997\08\12@085256 by Russell McMahon

picon face
> From: Mike <TakeThisOuTerazmusKILLspamspamspamWANTREE.COM.AU>
> >In a company with several thousand PCs, many of which are no-name clones
and
> >few of which are ever turned off (many sitting in labs unattended and
unused
> >for weeks or months at a timer), I don't think we've ever had a fire...
>
> Great - but, please understand that your sample size is still very low.
> rgds
> mike
> Perth, Western Australia

As a really rough rule of thumb the reliability of a random sample from
a normal distribution (ie the type we never see in nature :-)) is
p ~ SQRT(1/N)
so for a sample of "a few thousand" this is SQRT(1/2000) ~ 0.02
This is of course really really (really ...) rough but what it says is for
a
sample of a few thousand the real figure worst case is liable to be a few
% off what you measure (but of course in reality could be yonks off what
you measure due to non-statistical real world variation. Worst case
errors occur when the sample is around 50% and are tighter at either end.
In this case the sample is 0 (ie ...I don't think we;ve ever had..." so
this
suggests the result is liable to be fairly indicative.

That said, if my office is found burn't out tomorrow morn by a wayward
power supply, I won't be surprised!

1997\08\12@091943 by Mike

flavicon
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At 10:44 PM 8/12/97 +1200, you wrote:

>>         I was showing a friend what goes on here
>>         on the piclist.  Claiming this is the
>>         "geekiest thing ever," she has started saving
>>         it as a "shining example" of the extreme
>>         geekiness that can be achieved with the
>>         assistance of thousands of
>>         Programmers In Cooperation.

This just goes to show when we enter into dialectic that improves peoples
lives some '????ole' will think we are geeks - well bad luck !

>Well then, its nice to think that I originated this thread :-)
>(even if it was on a different topic originally!)

Yes it did sort of expand a bit - does happen...

>Does this make me a super geek?

Yep - like all well meaning engineers that don't take things for granted.

Rgds :)

Mike
Perth, Western Australia

1997\08\12@092335 by Mike

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At 12:11 PM 8/12/97 +0100, you wrote:
>Dear All
>I've left the copied body in for a reason.. Mike (perth) I believe you are
>quite wrong to splash so much bile across Glenns' comments.

Fine. The reason I was taken aback by his suggestion of "unscientific stupidy"
is that these sorts of formulas separate the human factor - we can all do
better to reduce risk - especially for the innocent, like our Children.

> The purpose of
>the threat formula is to aid in project and product planning in terms of
>risk to the project and the likely cost of alternative/extra action required
>to rectify in terms of time and capital. In such a context the formula is
>very valuable if simplistic.

How can it be valuable other than as a philosphical issue during debate,
one cannot ascribe numerics and expect them to have any practical basis or
how that influences me as to whether I link my smoke detector to a relay
that turns off the mains power - can you show me that ????????????????????

I have personal experiences of these formulas used as a substitute for
plain good thinking and the way these formulas are manipulated to save a
few pennies so the Director can get a new Jacusi is in so many respects
criminal.

> A good manager will have an idea of the
>relative weights of the RISK factor and possibly a good idea of the Harm
>factor but it is still imprecise and subjective and is thus not a rigorous
>rule.

Can your 'good manager' apply the numerics and make sense of them in any
human context and in any practical context - please supply example ?

> Your example of a plane crash is facile in this context.

No. In the general context you will see most plane crashes are caused by
accidents that could easily have been avoided had there been just a little
more care and a little more expense. Take the most recent ones; TWA in
USA - explosion of centre fuel tank (Why in the hell don't boeing use
inert gas purge - this is fundamental), Jumbo at Guam - failed navigation
and pilot assumptions, USA - cargo plane badly loaded/steep climb etc

>Please feel free to pick up any bok on project management, particularly
>software and teher it is in all its glory. (..or infamy) So in a way this is
>directly related to PIC projects

Hey - I've been through lots of books and find so much academic rubbish
that is so far removed from the human element, just because its a book
does not mean its passed any sort of critical analysis process. I have been
an academic myself back in 1980-84 (thereabouts) and operated my own
business since 1978 and have been exposed to so much dangerous thinking
by people who have been in their comfort zones and never taken responsibility
for the consequences of their actions.

I am dissapointed that in this modern age there is still so much dogma
and faith and wishful thinking. There are so many invalid presumptions
about the reliability of equipment thats its staggering.

Just because systems 'look like' they don't fail doesn't mean they don't
or that we should not take care. Remember this thread started in respect
of unattended operation of PC equipment using SMPSU.

Rgds

Mike
Perth, Western Australia

1997\08\12@101811 by Shane Nelson

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face
On Tue, 12 Aug 1997, Mike wrote:

> This just goes to show when we enter into dialectic that improves peoples
> lives some '????ole' will think we are geeks - well bad luck !

um. Everyone else seemed to realize it was a joke.
I can only hope that your reply was also.

We are geeks. It can't be helped.
Be proud of who you are :)
*grin*

-Shane.


Disclaimer: If you're not a geek, or
are offended by being called one,
then I wasn't referring to you;)

1997\08\12@114023 by Keith Dowsett

flavicon
face
At 08:19 12/08/97 -0600, you wrote:
>On Tue, 12 Aug 1997, Mike wrote:
>
>> This just goes to show when we enter into dialectic that improves peoples
>> lives some '????ole' will think we are geeks - well bad luck !
>
>um. Everyone else seemed to realize it was a joke.
>I can only hope that your reply was also.
>
>We are geeks. It can't be helped.
>Be proud of who you are :)
>*grin*
>
>-Shane.
>
>
>Disclaimer: If you're not a geek, or
>are offended by being called one,
>then I wasn't referring to you;)

If you don't know what kind of Geek you are see:

http://krypton.mankato.msus.edu/~hayden/.codes/geek3.1.html

Keith.

GAT/S d- s+:+ a C++ UL+ E- W++ N+ K- w+(---) M PS+EY PGP t5X+ R++ tv- b++
DI++ D+ G e++ h- r++ x+

------------------------------------------------------------
Keith Dowsett         "Variables won't; constants aren't."

E-mail: .....kdowsettspamRemoveMErpms.ac.uk  or RemoveMEkdowsettspamspamBeGonegeocities.com

WWW: http://kd.rpms.ac.uk/index.htm
    www.geocities.com/CapeCanaveral/Lab/8979

1997\08\12@162036 by Steve Smith

picon face
If the risk of fire in a SMPS is that high and the cost of smoke detectors is
so low the this leaves only one question,

Why are all SMPS fitted with their own smoke detector ?

This could have its own power source the power supply itself and sound an
alarm if the device catches fire !

1997\08\12@181856 by )

flavicon
face
Steve Smith wrote:

> If the risk of fire in a SMPS is that high and the cost of smoke
> detectors is
> so low the this leaves only one question,
>
> Why are all SMPS fitted with their own smoke detector ?
>
> This could have its own power source the power supply itself and sound
> an
> alarm if the device catches fire !
>
So how do you know how reliable the smoke detector is? You were thinking
these things are perfect?

Sorry. I've been watching this thread for days. Just couldn't resist any
longer.


Frank Richterkessing
Experimental Methods Engineer
GE Appliances

spamBeGoneFRANK.RICHTERKESSING@spam@spamspam_OUTAPPL.GE.COM

"The secret to good housekeeping -- Use low wattage bulbs!"

1997\08\13@003327 by blunn

flavicon
face
Bob Lunn
08/13/97 02:33 PM


>> The formula is THREAT = RISK * HARM
>
> This is the most unscientific rubbish I have ever seen and
> bears no relationship to reality...

    While the application of formulae is not in itself
    'scientific' it is certainly 'empirical'.  Empiricism
    is at the heart of engineering.

    The formula given is an attempt to mirror the _reality_
    of how people actually evaluate threats.

    Walking down the street on a sunny day I evaluate the
    threat of being struck by lightning as low.  Small risk
    by large harm equals little threat.

    Walking around a golf course in a thunderstorm I evaluate
    the threat of being struck by lightning as high.  Large
    risk by large harm equals 'get out from under this tree!'.

    As an engineer designs products to be used by others they
    have an obligation to evaluate the threats posed by that
    product.  The product's users are justified in requiring
    the engineer to evaluate those threats on the same basis
    as they themselves would.  That is, by quantifying the
    probability of an event and the cost of that event.

    That the quantification of risk and harm (probability and
    cost) will often be difficult or imprecise, or be based
    on rules-of-thumb, or be derived from anecdotal experience,
    does not exempt us as engineers from doing our sums.

> Would you ever quote this formula to the parent of a child killed
> in a plane crash...

    Mike, of course I would!  If I'm to be able to look that
    parent in the eye and know in my heart that I did my job
    as best I could, then I must be continuously evaluating
    threats as I design.

    Note the distinction here!  I am not _only_ minimising
    RISK, I am trying to minimise THREAT.  I am doing this
    because it most properly mirrors what that parent would
    do in my place (note that I am not saying that our
    respective quantifications of risk and harm would be
    the same).

    To minimise _only_ risk, or _only_ harm, is to fail in
    our professional duty.  To state as a moral imperitive
    (as you seem to do, Mike) that we should focus on the
    minimisation of risk is, I believe, to miss the point
    both morally and practically.

___Bob

1997\08\14@193810 by Eric Smith

flavicon
face
Mike <TakeThisOuTerazmusspamspamWANTREE.COM.AU> wrote:
> we can all do better to reduce risk - especially for the innocent, like our
> Children.

Does this mean that there are some people who aren't innocent, and thus
deserve to have their clock-radio or PC burn down their house?

And does it mean that children's lives are more valuable than those of adults?

This sort of thing annoys me greatly.  It reminds me of how, after the
Challenger disaster, lots of people complained about how terrible it was
because a teacher was on board.  Apparently one teacher's life is considered
more valuable than six astronauts' lives.

Even worse (IMNSHO) are the people who claim that dollar values can't be
placed on human life.  I presume that those people go out of their way to
buy cars with the 55 MPH bumpers that Ralph Nader was trying to get Congress
to mandate (the bumpers that are longer than the cars).  In the real world,
dollar values are placed on human life all the time.  It's not possible to
provide complete safety, and the more safety you want, the more things cost.
Even if you don't consciously consider it, every time you buy a potentially
dangerous product like a car, you *have* placed a value on life.  After all,
you could have bought a more expensive, safer car if you really wanted to.

Too bad no one makes peril-sensitive sunglasses yet.  Maybe they could be
PIC-based.  :-)

Eric

1997\08\14@235335 by blunn

flavicon
face
Bob Lunn
08/15/97 10:53 AM


>> The formula is THREAT = RISK * HARM
>
> This is the most unscientific rubbish I have ever seen and
> bears no relationship to reality...

    While the application of formulae is not in itself
    'scientific' it is certainly 'empirical'.  Empiricism
    is at the heart of engineering.

    The formula given is an attempt to mirror the _reality_
    of how people actually evaluate threats.

    Walking down the street on a sunny day I evaluate the
    threat of being struck by lightning as low.  Small risk
    by large harm equals little threat.

    Walking around a golf course in a thunderstorm I evaluate
    the threat of being struck by lightning as high.  Large
    risk by large harm equals 'get out from under this tree!'.

    As an engineer designs products to be used by others they
    have an obligation to evaluate the threats posed by that
    product.  The product's users are justified in requiring
    the engineer to evaluate those threats on the same basis
    as they themselves would.  That is, by quantifying the
    probability of an event and the cost of that event.

    That the quantification of risk and harm (probability and
    cost) will often be difficult or imprecise, or be based
    on rules-of-thumb, or be derived from anecdotal experience,
    does not exempt us as engineers from doing our sums.

> Would you ever quote this formula to the parent of a child killed
> in a plane crash...

    Mike, of course I would!  If I'm to be able to look that
    parent in the eye and know in my heart that I did my job
    as best I could, then I must be continuously evaluating
    threats as I design.

    Note the distinction here!  I am not _only_ minimising
    RISK, I am trying to minimise THREAT.  I am doing this
    because it most properly mirrors what that parent would
    do in my place (note that I am not saying that our
    respective quantifications of risk and harm would be
    the same).

    To minimise _only_ risk, or _only_ harm, is to fail in
    our professional duty.  To state as a moral imperitive
    (as you seem to do, Mike) that we should focus on the
    minimisation of risk is, I believe, to miss the point
    both morally and practically.

___Bob

1997\08\15@005426 by blunn

flavicon
face
Bob Lunn
08/15/97 02:25 PM


>> The formula is THREAT = RISK * HARM
>
> This is the most unscientific rubbish I have ever seen and
> bears no relationship to reality...

    While the application of formulae is not in itself
    'scientific' it is certainly 'empirical'.  Empiricism
    is at the heart of engineering.

    The formula given is an attempt to mirror the _reality_
    of how people actually evaluate threats.

    Walking down the street on a sunny day I evaluate the
    threat of being struck by lightning as low.  Small risk
    by large harm equals little threat.

    Walking around a golf course in a thunderstorm I evaluate
    the threat of being struck by lightning as high.  Large
    risk by large harm equals 'get out from under this tree!'.

    As an engineer designs products to be used by others they
    have an obligation to evaluate the threats posed by that
    product.  The product's users are justified in requiring
    the engineer to evaluate those threats on the same basis
    as they themselves would.  That is, by quantifying the
    probability of an event and the cost of that event.

    That the quantification of risk and harm (probability and
    cost) will often be difficult or imprecise, or be based
    on rules-of-thumb, or be derived from anecdotal experience,
    does not exempt us as engineers from doing our sums.

> Would you ever quote this formula to the parent of a child killed
> in a plane crash...

    Mike, of course I would!  If I'm to be able to look that
    parent in the eye and know in my heart that I did my job
    as best I could, then I must be continuously evaluating
    threats as I design.

    Note the distinction here!  I am not _only_ minimising
    RISK, I am trying to minimise THREAT.  I am doing this
    because it most properly mirrors what that parent would
    do in my place (note that I am not saying that our
    respective quantifications of risk and harm would be
    the same).

    To minimise _only_ risk, or _only_ harm, is to fail in
    our professional duty.  To state as a moral imperitive
    (as you seem to do, Mike) that we should focus on the
    minimisation of risk is, I believe, to miss the point
    both morally and practically.

___Bob

1997\08\15@011207 by Mike

flavicon
face
At 11:34 PM 8/14/97 -0000, you Eric Smith <ericEraseMEspamBROUHAHA.COM> wrote:
>Mike <RemoveMEerazmusEraseMEspamspam_OUTWANTREE.COM.AU> wrote:
>> we can all do better to reduce risk - especially for the innocent, like our
>> Children.
>
>Does this mean that there are some people who aren't innocent, and thus
>deserve to have their clock-radio or PC burn down their house?

No - of course not - what an idiotic suggestion, we are not debating wayward
political ideologies or selling futures in tupperware. No sane person would
for a moment entertain your observations (which have been snipped) which are
disgusting and may very well influence those of an immature disposition.

In respect of 'innocent' I am referring to those that are affected by
others 'outside the decision making loop'. When you take the responsibility
for your actions or suffer the consequences of your own decisions then
you are not the 'innocent' but others (the innocent) can be very seriously
affected, ie You would BE the person at 'cause' at hence NOT innocent.

In context with the original thread about leaving SMPS' turned on in
completely unattended situations - If you make a decision about the
reliability of a piece of equipment which does not involve others or
the potentially negative consequences then you can happily entertain
any risk you like - because clearly you just don't care.

However the reality is that it is very rare that any decision you
make about the use of OR engineering of any piece of equipment can
disregard the interests and safety of others - the innocents I am referring
to here are any other people that will have to bear the consequences
of your consideration (just by being in your presence) of what is risk
or hope or faith and its impact on the lives of all those you touch.

Rgds

mike
Perth, Western Australia

Truth is an elusive concept in the absence of a dogma.

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