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'Commercial vs. Industrail grade Integrated Circuit'
1999\03\14@214732 by Ry Lato

picon face
I am developing a consumer product that will operate in the trunk of
car.
My ideal goal is to use commercial grade integrated circuits wherever
possible.
Not only for cost reasons (Industrial grades of the some of the ICs I am
using are
2-3 times the cost), but the fact that Industrial grade versions of ICs
are more limited in availability, which could cause problems when
manufacturing
something in significant quantities. The product will be operating in
the trunk
of a vehicle. My concern with Commercial grade ICs is not the upper end,
since I can't see the trunk of a vehicle approaching much higher then
70deg c,
or 158 degrees farenheight. Its the lower end of 0 degrees C which is 32
deg F that concerns me. What happens to Integrated Circuits at
temperatures below 32 deg F that would cause a need to use an industrial
grade of an IC?
One way to prove my concern one way or another is by testing my product
in an environmental chamber for an extended period of time, which I will
do
in the future. For now I am just looking for some education on the
issue.

Get Your Private, Free Email at http://www.hotmail.com

1999\03\14@220024 by Wagner Lipnharski

picon face
You can be sure about this:

With certain exceptions and lucky fingers or whatever you
want to call it, most of the components, mainly high density
microchips works very marginal even at the manufacturer
specifications, if not fail before that.  Some of them
can work nicelly at the marginal stress points, and maximum
limits pointed by the manufactuer, but accelerating its
infant mortality.  You can hook up an environmental chamber
to run a chip specified as a maximum of +55¡C during 72
hours, but chances are you are reducing its end of life.

So, if you want to go to temperatures out of comercial grade,
just don't lose time, brain, your sanity, just don't think
twice, go to industrial grade, or in your case, automotive
grade... perhaps military...  It is better to have delivery
and availability problems than "product" problems.

Remember, your environmental chamber needs to simulate all
the automotive functions, even vibration, bumps, humidity,
temperature, "kids fingers, gum, candy melting on the back
seat cup holder..." :).
--------------------------------------------------------
Wagner Lipnharski - UST Research Inc. - Orlando, Florida
Forum and microcontroller web site:  http://www.ustr.net
Microcontrollers Survey:  http://www.ustr.net/tellme.htm

1999\03\14@220230 by Peter Grey

picon face
At 06:45 PM 14/03/99 PST, you wrote:


I hope you are not going to sell these in Australia. Temperatures in the car
will definitely exceed 70 degrees C.


Peter Grey
{Quote hidden}

1999\03\14@221333 by Gerhard Fiedler

picon face
At 18:45 03/14/99 -0800, Ry Lato wrote:
>of a vehicle. My concern with Commercial grade ICs is not the upper end,
>since I can't see the trunk of a vehicle approaching much higher then
>70deg c, or 158 degrees farenheight.

i don't know where you sell your stuff, but on a sunny day here in san
diego, ca, usa, you can fry eggs on your trunk. (it's not for nothing that
they introduced an intermediate range between "commercial" and "military"
and called it "automotive"... :)

>Its the lower end of 0 degrees C which is 32
>deg F that concerns me. What happens to Integrated Circuits at
>temperatures below 32 deg F that would cause a need to use an industrial
>grade of an IC?

i guess what happens, generally speaking, is that something has a good
chance to go out of specs. it's about the same as with overclocking: it
probably works in many cases, but you'll never know, because you're outside
of the quality control of the producing chain.

ge

1999\03\14@225349 by Wagner Lipnharski

picon face
Gerhard Fiedler wrote:
> i don't know where you sell your stuff, but on a sunny day here in san
> diego, ca, usa, you can fry eggs on your trunk. (it's not for nothing that
> they introduced an intermediate range between "commercial" and "military"
> and called it "automotive"... :)

...wanna try Central Florida???
I produced a device to analyze solar radiation, it needed to stay in the
open weather for a week for tests, in August, the ABS case melted, and
the battery pack wrap plastic just broke and shrink as if the temp
inside the case was around 150¡F (65¡C), when I took it back inside, it
needed to cool down for at least 10 min in the air conditioned to be
able to touch the batteries... can you imagine?  No one microchip got
damaged or any problems at all, even with commercial grade it worked
pretty nice, even the data stored at the e2prom was ok. Opening the
case, the smell was some like burned wire insulation. Atmel parts. I
guess I was purely lucky, huh?
--------------------------------------------------------
Wagner Lipnharski - UST Research Inc. - Orlando, Florida
Forum and microcontroller web site:  http://www.ustr.net
Microcontrollers Survey:  http://www.ustr.net/tellme.htm

1999\03\15@014232 by Gerhard Fiedler

picon face
At 22:52 03/14/99 -0500, Wagner Lipnharski wrote:
>...wanna try Central Florida???

to say the truth, i probably would prefer coastal florida :)

>case, the smell was some like burned wire insulation. Atmel parts. I
>guess I was purely lucky, huh?

i guess, too. OTOH, most parts seem to withstand quite a bit out-of-spec
handling :)  but as you (and many others here before) said, better not rely
on it if you don't have to...

ge

1999\03\15@032414 by Lee Jones

flavicon
face
> I am developing a consumer product that will operate in the
> trunk of car.  My ideal goal is to use commercial grade ICs
> wherever possible.

> My concern with Commercial grade ICs is not the upper end,
> since I can't see the trunk of a vehicle approaching much
> higher then 70 deg c, or 158 degrees farenheight.

If you're planning on selling anywhere in the southwestern
US (eastern southern California, Nevada, Arizona, New Mexico,
or west Texas), 70 deg C vehicle sheet metal is a reality.
If you have any low thermal resistance path to your chips,
you may start seeing product failures and returns.

Will you have control over how & where in the trunk the
device is installed?

Another thing to remember, is that most parts are built on
a single fabrication line.  They are binned into various
grades by testing.  So any given group of a commercial IC
will likely have a higher percentage of parts barely able
to function at the extremes of that temperature range.

                                               Lee Jones

1999\03\15@090957 by mlsirton

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face
Hi all,

On 14 Mar 99 at 18:45, Ry Lato wrote:
<snip>
> My ideal goal is to use commercial grade integrated circuits wherever
> possible.
<snip>

I've been following this discussion with interest...
Our local Microchip distributor doesn't stock Industrial grade OTP
12C508.  When I asked him why he said that "everybody" just uses the
commercial grade instead and that they are actually the same chip, no
screening or anything.
So I went and ordered the parts I needed from Digikey (industrial).
But I still wonder...

How would they screen the chips anyways in case the higher
temperature range would just cause reduction of the IC's lifetime?
(Assuming the same wafer is used...)
And what's the deal with 12C508A and 12LC508A?  Smaller geometry =
lower voltage and lower current?  So how come the datasheet indicates
higher typical Icc for the 508A than the 508?

Guy - spam_OUTmlsirtonTakeThisOuTspaminter.net.il

1999\03\15@091408 by Clark, John

picon face
       >>So how come the datasheet indicates higher typical Icc for the
508A than the 508?

The best reason I have heard on this list so far is the more precise clock
of the 508A needs more power for this increased stability.

I would like to hear the "official" explanation.


John Clark, Software Engineer
.....JohnCKILLspamspam@spam@inter-intelli.com
(317) 715-8175 (voice & fax)

Interactive Intelligence, Inc.
3500 DePauw Blvd., Suite 1060
Indianapolis, IN  46268-1136
http://www.inter-intelli.com

> {Original Message removed}

1999\03\15@171527 by Graeme Smith

flavicon
face
Here in Canada we see both ends of the spectrum....

People keep Frying their dogs in the passenger compartment, because they
forget to open the windows to allow a little ventilation... (Is the trunk
ventilated?) And, of course, during an extreme winter, it can get down
to 100 below, plus have a wind chill, of 20 or 30 degrees...

Needless to say, even the "Automotive Grade" chips, have a reduced
life-span. I often wondered if it might pay to build the circuit on an
electro-thermal device, and use it for "Pumping the heat" which ever
direction is needed, and thus setting the circuit temperature into an
operating range.... might be a drain on the battery, but it would keep
your vital circuits from freezing.

The primary problem as far as I can tell, with extremes of temperatures
has to do with the substrate of the chip itself. As it gets colder it
contracts, and as it gets warmer it expands. However because the materials
we dope with have a different co-efficient of expansion/contraction the
chip does not expand and contract evenly across the substrate, causing
stress in the crystal latice, that acts to build up, and create flaws in
the crystal surface where there is high stress. Over a period of heating
and cooling cycles, such as is found in a Canadian Car, the crystal is
flexed over and over again, widening any flaws, and soon, acting to
separate actual components, or traces from the rest of the circuilt.

The result, is that over time, the chip becomes progressively more and
more faulty, and some of its functions fail, with eventual death of the
circuit, much faster than would be expected even in places with
consistently hot weather.

Does this help?

                               GREY

GRAEME SMITH                         email: grysmithspamKILLspamfreenet.edmonton.ab.ca
YMCA Edmonton

Address has changed with little warning!
(I moved across the hall! :) )

Email will remain constant... at least for now.


On Sun, 14 Mar 1999, Gerhard Fiedler wrote:

{Quote hidden}

1999\03\15@175553 by Dave VanHorn

flavicon
face
>People keep Frying their dogs in the passenger compartment, because
they
>forget to open the windows to allow a little ventilation... (Is the
trunk
>ventilated?) And, of course, during an extreme winter, it can get
down
>to 100 below, plus have a wind chill, of 20 or 30 degrees...


But chips don't do "wind chill"...

1999\03\15@191052 by Gerhard Fiedler

picon face
At 15:13 03/15/99 -0700, Graeme Smith wrote:
>Needless to say, even the "Automotive Grade" chips, have a reduced
>life-span. I often wondered if it might pay to build the circuit on an
>electro-thermal device, and use it for "Pumping the heat" which ever
>direction is needed, and thus setting the circuit temperature into an
>operating range.... might be a drain on the battery, but it would keep
>your vital circuits from freezing.

i remember faintly a story about (big) cranes in russia, where they had a
sequence of three heating devices (from small heater to big heater)
starting in sequence: first a small heater heated a small motor which then
started to drive a generator to heat the tank and the motor of the next
bigger stage and so on...

ge

1999\03\15@192130 by Gerhard Fiedler

picon face
At 17:52 03/15/99 -0500, Dave VanHorn wrote:
>But chips don't do "wind chill"...

this was my first thought, too, but think of two things: what happens when
they get some moisture on them? as long as they're working this seems
unlikely, but shut down... and the other is that we're talking here about
temperatures possibly below the chip's temperature (as long as they're
working). and that's exactly the "wind chill situation" (meaning that a
chip exposed to moving air below its temperature has to produce more heat
to keep the temperature than exposed to the same air without movement).

ge

1999\03\15@205112 by Wagner Lipnharski

picon face
Graeme Smith wrote:
> The primary problem as far as I can tell, with extremes of temperatures
> has to do with the substrate of the chip itself. As it gets colder it
> contracts, and as it gets warmer it expands. However because the materials
> we dope with have a different co-efficient of expansion/contraction the
> chip does not expand and contract evenly across the substrate, causing
> stress in the crystal latice, that acts to build up, and create flaws in
> the crystal surface where there is high stress. Over a period of heating
> and cooling cycles, such as is found in a Canadian Car, the crystal is
> flexed over and over again, widening any flaws, and soon, acting to
> separate actual components, or traces from the rest of the circuilt.
>
> The result, is that over time, the chip becomes progressively more and
> more faulty, and some of its functions fail, with eventual death of the
> circuit, much faster than would be expected even in places with
> consistently hot weather.

This may be one of the reasons that nature selected organic life forms
to populate the planet and not anyother, like crystaloid structures. We
can expand and contract under temperature (or wife's pressure) without
our bones being detached from our body's structure...:)

Are you suggesting that this is the reason for the research about
electronic gates based on polymeres instead silicon? Flexibility in
extreme temperature situations?

How they solved this problem in cryogenic processors? I mean, during
certain time, for maintenance or something, it needs to warm back to
ambient temperature, right? they are too expensive to risk the
electronics with contraction/expansion problems.

The Josephson technology for example, it uses macrochips (not micro)
that its connection leads (pins) just enter in small holes filled with
liquid mercury (metal) at room temperature. Liquid Nitrogen puts it to a
very low temperature and as the liquid mercury is the last to contract
and get solid, it fulfill the cavity doing a very good electric contact
between the macrochip pin and the board. I am not sure about that, I saw
a presentation years ago.  But the question is about how that kind of
electronics can stand so low temperature without cracking and just
separate the internal layers of different crystal structures inside the
chips...
Wagner

1999\03\16@033917 by Mark Willis

flavicon
face
Be glad you don't do Arctic sensor packages, or avionics;  -40C is
sorta rough on some IC's <G>  Space-certified parts, basically, are what
you need, a little hard to find 1's and 2's of those for samples.  You
can use Industrial parts to get the circuit running initially,
fortunately!  Automotive's bad enough, though...

 Add running off a Zinc-Aire battery and things get quite fun (Those
need to self-heat when cold before you can draw much current from them,
yet another detail to handle.)

 IIRC Wind chill requires evaporation of water;  Unlikely, as Dave said
<G>

 Mark

1999\03\16@140923 by Gerhard Fiedler

picon face
At 18:49 03/15/99 -0800, Mark Willis wrote:
>  IIRC Wind chill requires evaporation of water;  Unlikely, as Dave said
><G>

i guess the most part of the "wind chill" is due to the fact that heat
conduction gets a lot better with moved air (that's why some guys put fans
in their computer -- those chips and power supplies sure do get some "wind
chill" :)  you feel wind chill even through completely water-proof gear,
where there should be almost no evaporation, at least not where the wind
(and the cold) hits, and you feel it with 100% humidity, too, where there
should be almost no evaporation, either.

wind "chill" is not only the effect that cold air (colder than the body)
seems colder with wind (the more common case), but also that hot air
(hotter than the body) seems hotter with wind (more rare in these regions
where most of us live, but i'm sure one or another can confirm that this is
actually true) -- it's only that the expression was coined -- where? but
for sure somewhere around the usa or the uk :) , and not in the sahara.

ge

1999\03\16@153236 by Wagner Lipnharski

picon face
Heat is a molecular oscillation, excitation, vibration, zero Kelvin
(-273¡C) is a complete oscillation stop (is that right?). Heat is
transferred by transmitting this oscillation, while it is wrong to think
that you can transmit cold temperatures, in real you are taking off the
oscillation of high temperatures.

To remove or apply oscillation (heat), you need to use a transport
element, with more or less oscillation than the subject object.

The molecular oscillation try to accommodate and stop its oscillation
naturally along with the time, and this is why all objects in deep
space, far from any heat source (stars) goes to a deep cooling
temperature. The oscillation just go away, in form of radiation or other
way.

Back here on earth, wind and water is the most common molecular
oscillation transport system. If you take a hot piece of iron and keep
it cooling in the room air, it will transfer that oscillation (heat) to
the air that is immediately close to the metal.  The air molecules with
absorbed temperature will oscillate more, what makes it expand in size,
using more space (volume) and turns to be expulsed toward where the
pressure is small, it means upward. So the hot air will go up and fresh
air will go near the hot metal, again taking part of that oscillation
and the cycle repeat again, until the hot metal delivered all its
"difference" in oscillation from the rom air, and they enter in an
"equilibrium" what makes both oscillate in the same rate, with very few
transferring from one to another.  The speed of how this "transport"
system happens, makes the subject element cools or heats faster or
slower. This is why moving air around a hot subject with a fan, normally
cools it down, except if the air is at the same temperature, what will
change absolutely nothing.

Materials with high heat vibration transportability, as metals, looks
always cooler than they are. When we touch a piece of aluminum or steel,
the heat at our fingers (the vibration) is transfered easily to the
metal, and we loose temperature, so we fill it cooler than when we touch
a piece of wood for example, even that the wood and the metal would be
at the same room temperature.

As faster a transport element moves the molecular oscillation in its
material, better "heat radiator" it is. Normally metals can do a great
job, and if the "heat radiation" needs to be exchanged with air, as much
area in contact with air, faster the transport is done. This is why
transistor and other heat radiators have those several wings and
"antennas style", just to increase its contact (transport) area.

Some radiators are painted in black, because black is the color that
doesn't reflect any color, or other visible radiation, it is very nice
to absorb heat, but to transmit it?  I doubt that. I can be wrong, and I
would like to see an explanation about its efficiency.

In a closed system, there is no molecular vibration transport system,
coolers, and temperature containers,
the usual lunch box. This is why it keeps temperature.

IBM used a cool water system to refrigerate the heat transport system in
the 3081 mainframes chips.  The interior of the chips (on top of that)
have little pistons mechanically removing heat from the silicon,
transporting it to liquid helium (or it was nitrogen?) that gets its
heat transferred to the cool water, that goes to another heat exchange
system to an out-of-machine water cooling system supplied by the
customer.
It is pretty interesting to see the movie about this things working,
simply fascinating.

The real problem with high density microchips is that it generates large
heat in a very small spot, very difficult to remove that concentrated
heat.  This is the main reason to reduce power consume, and drop supply
voltage to 3V and so on. The heat is reduced.  Technically it is
possible to produce smaller and smaller microchips, but the heat removal
problem holds this possibility.  If you imagine a PIC core consuming 5mA
at 5V, it is 25mW into a cubic millimeter (aprox). Doing a comparison in
size, a cubic inch has aprox 16,387 cubic millimeters, so it would be
equivalent to have 409Watts of heat dissipating in a cubic inch.
Imagine 4 lamps of 100W heating inside of a cubic inch piece of metal,
try to hold it in your bare hands...  The substrate and the connection
wires helps to remove this heat.  What would be the real temperature in
the exact center of that cubic inch metal? almost melting, right? This
is almost what happens into microchips.

Some automatic "transport molecular vibration system" can be implemented
to help circuits to works around extreme temperatures, hot or cool. A
protective temperature system using some anti-heat-transport can be used
and it will keep the internal temperature more stable for long time in
the winter, also in the summer, but then the chip will need a cooling
system too.  

So, why not use the actual existent temperature control system in any
car, the water cooling system?
The temperature of the water radiator exit is not too hot, and if it is,
a simple water derivation will cool it down enough to warm up a metal
box base where the electronics could be inside.  This system could be
inserted into a thermo enclosure with a thermo valve that allows water
to enter only after some temperature, while a resistive heating device
could heat this thermo box when starting the car into cooling mornings.
A cost of a system like that is small, and can ensure a long life to the
electronics.  Even with changes in temperature, the different materials
inside the microchip will suffer less, since the temperature variation
would be very slow, allowing it to accommodate better the mechanical
movement.

I believe that even the military versions suffer with this temperature
extremes.

I don't understand very well how different materials transport this heat
vibration in different rates, I think I did skip school that day.
Perhaps somebody else can explain it.  I believe this is called
"thermodinamyc".

here my 2 cents... :)

1999\03\16@163834 by Gerhard Fiedler

picon face
At 15:30 03/16/99 -0500, Wagner Lipnharski wrote:
>Materials with high heat vibration transportability, as metals, looks
>always cooler than they are. When we touch a piece of aluminum or steel,
>the heat at our fingers (the vibration) is transfered easily to the

only if the metal is cooler than the finger. hot metal "looks" hotter than
it is (compared to, say, air), for the same reason :)  you can put your
hand easily (for a limited amount of time) in an oven with a temperature of
200¡C. i wouldn't advice touching any of the walls, though -- even though
they are at the same temperature.


>So, why not use the actual existent temperature control system in any
>car, the water cooling system?
>The temperature of the water radiator exit is not too hot, and if it is,
>a simple water derivation will cool it down enough to warm up a metal
>box base where the electronics could be inside.

on a nice sunny day, maybe going up the mountain (not in florida, though
:), you'd probably exceed 70¡C in the cooling system, don't you think?

>to enter only after some temperature, while a resistive heating device
>could heat this thermo box when starting the car into cooling mornings.

there is a problem with this. if your device has to work before the car
starts or independently of the motor, battery power is =scarce= in these
situations. motor-independent gas or diesel heaters (burners to heat the
motor coolant) use this to preheat the combustion chamber before they
start. but they then heat up the motor, so it starts pretty easy and needs
a lot less battery power to start. when it's cold, the battery capacity
goes down, you use a lot of power hungry devices in the car all the time
(lights because it's dark a lot, rear window defogger, fan, wiper) so the
battery often does not get the charge it needs, the max. current it can
provide for the starter goes down (which means that the battery loading
state must be better for the same current draw), and the motor needs more
time to start. so you have to be very careful to drain the battery power,
=especially= when it is cold (because it's not only "cold," it's the
combination of many factors that usually come with it when it's cold).
(just to clarify: i'm not talking about chilly mornings in central florida
here :)

>A cost of a system like that is small, and can ensure a long life to the
>electronics.  Even with changes in temperature, the different materials
>inside the microchip will suffer less, since the temperature variation
>would be very slow, allowing it to accommodate better the mechanical
>movement.

i'm not sure that this would enhance life time. to me it seems that the
temperature changes of the coolant are more than for the rest of the car,
in most situations. every time you start your car it goes right up from
below 20¡C to above 70¡C, in a pretty short time. it takes more time to
cool down, but it still seems like quite some temperature cycling to me --
more an endurance test than a comfortable, life-time prolonging situation :)

ge

1999\03\16@182822 by g.daniel.invent.design

flavicon
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Ever heard of black body radiation ?
If black objects were unable to radiate heat effectivly, then we would
be relying purely on convection and conduction to cool them down again.

As an experiment Wagner, get two heatsinks, paint one white, and the
other black. Place both in water and boil for a while. I have no doubts
that you will find the black one cools faster, also hold a safe distance
from your face, the black one will warm your face.

The problem with all this theory, is that we are not able to test most
of it with our own senses, if for example we were able to see in
wavelengths to +&- 10^2 of our current range, I can assure you that
there would be far fewer secrets in the world.
regards,
Graham Daniel.

Wagner Lipnharski wrote:
<cut>
{Quote hidden}

<cut>
This is ideal use for "Heat pumps"
use a tube with wick inside and thermally conductive attachment points
each end. fluid in wick evaporates at hot end, condenses at cold.



--
Steam engines may be out of fashion, but when you consider that an
internal combustion engine would require recovery of waste heat by
transfer just before top dead centre then fashion becomes rather
redundant, USE STRATIFIED HEAT EXCHANGERS ! and external combustion.

You heard it first from: Graham Daniel, managing director of Electronic
Product Enhancements.
Phone NZ 04 387 4347, Fax NZ 04 3874348, Cellular NZ 021 954 196.

1999\03\17@201404 by Graeme Smith

flavicon
face
GRAEME SMITH                         email: .....grysmithKILLspamspam.....freenet.edmonton.ab.ca
YMCA Edmonton

Address has changed with little warning!
(I moved across the hall! :) )

Email will remain constant... at least for now.

D. Vanhorn said
>
> But chips don't do "wind chill"...
>
You think that a metal trunk, doesn't cool off with WIND CHILL???

Perhaps you never turned your car radiator into the wind, and found it
impossible to start, because of "Wind Chill"....

chips don't do wind chill.... Sheeesh [G]

                               GREY

1999\03\18@023137 by Mark Willis

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face
Graeme Smith wrote:
{Quote hidden}

 The difference between a person & a PIC is that a PIC doesn't
"perspire", so while convection and conduction still cool it,
evaporation doesn't.  For humans, evaporation can be pretty significant
(Go wear cotton and exercise outdoors on a cold dry day, and tell me
where the water in your clothes came from, if you don't think humans
sweat in cold weather <EG>  I'll stand near you, observing, in my nice
wools <G>)

 Evaporation definitely is part of observed temperature, check out a
wet bulb versus a dry bulb thermometer on that same day...

 Mark

1999\03\18@102812 by Wagner Lipnharski

picon face
Graeme Smith wrote:
> Perhaps you never turned your car radiator into the wind, and found it
> impossible to start, because of "Wind Chill"....

I do that all the time, never got a problem... I live in Florida... :)
Wagner.

1999\03\18@105119 by Wagner Lipnharski
picon face
Mark Willis wrote:
>   Evaporation definitely is part of observed temperature, check out a
> wet bulb versus a dry bulb thermometer on that same day...
>
>   Mark

Human body can generate heat easily, but can't cool down fast, so it
needs to "dump out something that can transport heat", easily to do with
water, perspiration, when the internal temp reaches some point. Some
people just don't realize how much damage they can do to the system just
blocking that function, with plastic and
not transpirable clothes... I wonder if they block their Computer power
supply fan to make the machine works faster too... There is a lot of
confusion and info mixup about loose water and/or fat. You can burn the
same quantity of calories/fat retaining or not the transpirated water.
It is interesting that some other species control it in different ways,
dogs for example, they don't have this transpiration system, they use
their tongue as the transpirator.

I wonder if we could do some holes in a pic microchip...pour water...and
see it sweat :) What about a hairy one?  "Perspirable Integrated
Circuit" ?

Wagner

1999\03\18@141053 by Sean Breheny

face picon face
At 06:11 PM 3/17/99 -0700, you wrote:
>D. Vanhorn said
>>
>> But chips don't do "wind chill"...
>>
>You think that a metal trunk, doesn't cool off with WIND CHILL???

Yeah,but it is a different effect. The fact that the wind doesn't allow
warm air to build up around the trunk allows is to cool faster. The effect
is MUCH more pronounced,I would think,when water is involved,because then
not only do you have convection,but you also have evaporation at the same
time,and the heat of vaporization of water is pretty substantial. So,my
guess is that if the wind chill factor is 10 degrees (below the actual air
temp) for things involving evaporation,it is probably only about 1.5
degress below the air temp for just a warm piece of metal(these aren't
actual numbers,just a qualitative guess). In addition, a PIC doesn't have
all that much surface area,unless you add a heat sink. This will alter the
effect,too.

>
>Perhaps you never turned your car radiator into the wind, and found it
>impossible to start, because of "Wind Chill"....

Well,with the radiator,you have ALOT more surface area.

>
>chips don't do wind chill.... Sheeesh [G]

How did the expression "xxx doesn't do xxx" get into the common
vocabulary,anyway? <G>
e.g. "Lets DO lunch."

>
>                                GREY
>

Sean

|
| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
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1999\03\18@175936 by rweaver8

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I must agree that a non perspiring and not wet item will not detect
wind chill. I have to use wet and dry bulb thermometers in my egg
incubators. I wanted to try to find out what the actual egg internal
temperture was as the dry bulb thermometers were too sensitive to the
change in air A wet bulb read too low as the evaporation of the water
cooled it .Finally I decided that to stop the water from evaporating I
could put a latex glove over a bottle filled with water and used a stem
thermometer to poke through the latex and form a seal around it. As the
evaporation was stopped the temperture raised up to near the temperture
of the dry bulb. But because the water did not give up its heat as
easily as the humid air it did not swing as rapidly as the dry bulb.
Just my 2 cents

Ralph
Mark Willis wrote:
{Quote hidden}

1999\03\18@202637 by Gerhard Fiedler

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At 15:55 03/18/99 -0700, Ralph Weaver wrote:
>I must agree that a non perspiring and not wet item will not detect
>wind chill.

there seems to be some confusion about "wind chill" and evaporation cooling.

every liquid has a tendency to evaporate, and while evaporating, the energy
to transform the liquid into a gas is taken from the surrounding, cooling
it down. the amount of evaporation depends on the wind and on the relative
concentration of the evaporating substance in the wind. in a tropical
rainforest, with 100% relative humidity, you still sweat a lot, but you
don't get almost any evaporation cooling, with no amount of wind.

so, water evaporation cooling has one component which is part of the "wind
chill," which is the amount water evaporation increases with air movement,
and one which is not part of the "wind chill," which is the part present in
still air, and both depend on the relative humidity.


our temperature perception is not primarily based on the temperature of the
surrounding, but on the temperature on (or better within) the surface of
our skin. this temperature is a function of the energy flow from the body's
heated parts to the surrounding, and this energy flow depends basically on
two factors: the temperature difference and the thermal resistance. wind
dramatically decreases the thermal resistance, even when dry, and that's
the second main component of "wind chill." but this part of "wind chill"
has the effect to make air hotter than the body seem hotter when it's
moving than when it's still, which is not exactly a "chill" :)

a practical example that this type of "wind chill" actually works without
perspiration are the fans in a computer. without them, some components
would feel quite a bit less "chilly." (of course one could enhance the
cooling effect by keeping the surfaces moist. rather impractical in most
cases, but probably a lot more quiet :)


now, with thermometers you don't get any "wind chill" of the second type,
because when you're measuring, the thermometer is (or is supposed to be) at
the temperature of the surrounding, which means that the thermal resistance
is not significant (only for the time it takes the thermometer to show the
temperature). but of course you get evaporation cooling if the thermometer
is wet, even when there is no air movement. and the evaporation cooling
increases with air movement, which then is part of the "wind chill" as the
expression is commonly used (applied to human temperature perception).


i would suspect that the common "wind chill" tables take primarily the
second factor into account (the thermal resistance), because the
evaporation cooling depends on too many other factors (primarily the amount
of humidity on the skin and the relative humidity in the air) to be able to
give any reasonable general estimate for it without taking them into
account. and these tables usually have only the temperature and air speed
as variables.

ge

1999\03\18@223249 by rweaver8

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Wagner Lipnharski wrote:
>
> Graeme Smith wrote:
> > Perhaps you never turned your car radiator into the wind, and found it
> > impossible to start, because of "Wind Chill"....
>
> I do that all the time, never got a problem... I live in Florida... :)
> Wagner.

Some years ago I was working in Wyoming in the winter. I had a 50/50
antifreeze mix in my radiator. According to the instructions on the
antifreeze bottle this will protect to 34 below zero. On several
mornings I went out and found that the temperture was 40+ below zero. As
I had prepared for winter and had a good battery, a well tuned engine
and engine oil of the 10w 40 grade I never had a problem. I was however
concerned about the antifreeze in the engine. I opened the radiator cap
and observed the coolant. It was slushey. When the engine started and
the fan pulled the cool air across the fins of of the radiator it did
not get thicker as the engine warmed the slushieness disappeared.
       The main factors in an engine being hard to start when cold are: the
cold makes the oil get thicker and it offers greater resistance to the
movement of the parts. The second factor is the battery apears to have
less voltage when it is colder. This can be verified by putting a
flashlight battery in the freezer and leaving it for 30 minutes then
take a reading with a volt meter. Record it then with for the battery to
reach room temperture and take another voltage reading. When these
things combine plus an engine being not tuned 100% right it will make
your engine almost impossible to start. A little trick is I learned many
years ago  when its very cold turn your head lights on for abot 30
seconds before attempting to start your car. The chemical action within
the battery will warm it some and the voltage will raise. Turn off the
lights and only then start your car.

Ralph

1999\03\19@163723 by John Payson

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|i remember faintly a story about (big) cranes in russia, where they had a
|sequence of three heating devices (from small heater to big heater)
|starting in sequence: first a small heater heated a small motor which then
|started to drive a generator to heat the tank and the motor of the next
|bigger stage and so on...

Awhile ago, on the radio news, I heard that temperatures in Alaska
got down to -80 (not sure if that's F or C... cold either way!) and
basically if your car or furnace stopped it wasn't going to start
again until the weather warmed up.  Even a gravity-operated oil furnace
won't work too well if the oil is solidified...

Rather amusingly, however, this news report was followed (after a short
station promo) by an advertisement for Royal Carribean Cruise Lines'
Alaskan tours...


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