Presumably, one should feel comfortable using a device at the
published operating temperature extremes "forever".
But, what sort of derating likely went into that specification
in the first place? Sad another way, how much *beyond* those
limits might want suspect you could operate the device?
Presumably, one should feel comfortable using a device at the
published operating temperature extremes "forever".
But, what sort of derating likely went into that specification
in the first place? Sad another way, how much *beyond* those
limits might want suspect you could operate the device?
On Mon, 3 Jun 2024 07:52:58 -0700, Don Y <blockedofcourse@foo.invalid>
wrote:
Presumably, one should feel comfortable using a device at the published >>operating temperature extremes "forever".
But, what sort of derating likely went into that specification in the
first place? Sad another way, how much *beyond* those limits might want >>suspect you could operate the device?
I don't think that there are any standards that manufacturers use to
make datasheet abs max specs.
I like to test parts to destruction and estimate what they can actually
do. For example, max voltage ratings can sometimes be safely exceeded,
or a surface-mount resistor can dump a lot of power if it's well heat
sunk with copper pours.
Thermal imaging can quantify hot-spot temperatures.
Pushing parts past specs is only a good idea if there is a serious performance upside.
RF parts are especially likely to be under-rated. Like a 2 volt rated schottly detector diode that starts to leak at 7. Or RF amp parts that actually run at 2x rated max voltage in normal use.
GaN fets are interesting. As are mosfets that avalanche at some
unspecified voltage.
A bit of air flow can really change things. I assume that most specs are based on still air.
I've seen a few parts that were unreliable within their abs max specs
and needed to be derated from there.
Blow up some parts. It's fun.
On Mon, 03 Jun 2024 09:03:10 -0700, john larkin wrote:
On Mon, 3 Jun 2024 07:52:58 -0700, Don Y <blockedofcourse@foo.invalid>
wrote:
Presumably, one should feel comfortable using a device at the published >>>operating temperature extremes "forever".
But, what sort of derating likely went into that specification in the >>>first place? Sad another way, how much *beyond* those limits might want >>>suspect you could operate the device?
I don't think that there are any standards that manufacturers use to
make datasheet abs max specs.
I like to test parts to destruction and estimate what they can actually
do. For example, max voltage ratings can sometimes be safely exceeded,
or a surface-mount resistor can dump a lot of power if it's well heat
sunk with copper pours.
Some fellow on Youtube a while back managed to get a kilowatt out of a
TO-220 packaged device rated at 100W by blasting it with plumber's Arctic >Spray.
Thermal imaging can quantify hot-spot temperatures.
Pushing parts past specs is only a good idea if there is a serious
performance upside.
RF parts are especially likely to be under-rated. Like a 2 volt rated
schottly detector diode that starts to leak at 7. Or RF amp parts that
actually run at 2x rated max voltage in normal use.
Probably because it's common in RF to end up with the part being subjected
to voltages double its normal supply rail figure.
GaN fets are interesting. As are mosfets that avalanche at some
unspecified voltage.
A bit of air flow can really change things. I assume that most specs are
based on still air.
I've seen a few parts that were unreliable within their abs max specs
and needed to be derated from there.
Blow up some parts. It's fun.
Best fun you can have with your clothes on as they say.
Presumably, one should feel comfortable using a device at the
published operating temperature extremes "forever".
But, what sort of derating likely went into that specification
in the first place? Sad another way, how much *beyond* those
limits might want suspect you could operate the device?
On 6/3/2024 7:52 AM, Don Y wrote:
Presumably, one should feel comfortable using a device at the published
operating temperature extremes "forever".
But, what sort of derating likely went into that specification in the
first place? Sad another way, how much *beyond* those limits might
want suspect you could operate the device?
Well, a quick canvas of colleagues suggests derating isn't even a consideration! Rather, that the operating environment is used to drive
the design, with no real effort to quantify actual device operating
limits:
"We know the characteristics of the components that we
use and the general characteristics of the enclosure to convince
ourselves that we can meet the expected operating temperature range"
And, what exactly *is* that range?
"<mumble>"
Amusingly, for consumer devices, you rarely even see these limits
published. Or, KNOW that they are bogus;
- TVs claiming 5-35C - cordless phones 25C +- 10 - HiFi kit with NO environmental constraints - laptops?
- cell phones (95F with storage to 113 means "not here"!)
So, all of the TVs mounted (here) in garages or on back porches have
been inoperable once the outdoor temperature exceeded 100F?
And, don't dare walk outdoors with your cordless phone or $1000 cell
phone lest it stop working mid call
HiFi? Will it quit at 76F? or 62F?
It's amusing that folks don't seem to know the constraints of the
devices they are producing!
On Mon, 3 Jun 2024 21:41:59 -0000 (UTC), Cursitor Doom <cd999666@notformail.com> wrote:
On Mon, 03 Jun 2024 09:03:10 -0700, john larkin wrote:
On Mon, 3 Jun 2024 07:52:58 -0700, Don Y <blockedofcourse@foo.invalid>
wrote:
Presumably, one should feel comfortable using a device at the
published operating temperature extremes "forever".
But, what sort of derating likely went into that specification in the >>>>first place? Sad another way, how much *beyond* those limits might >>>>want suspect you could operate the device?
I don't think that there are any standards that manufacturers use to
make datasheet abs max specs.
I like to test parts to destruction and estimate what they can
actually do. For example, max voltage ratings can sometimes be safely
exceeded, or a surface-mount resistor can dump a lot of power if it's
well heat sunk with copper pours.
Some fellow on Youtube a while back managed to get a kilowatt out of a >>TO-220 packaged device rated at 100W by blasting it with plumber's
Arctic Spray.
Thermal imaging can quantify hot-spot temperatures.
Pushing parts past specs is only a good idea if there is a serious
performance upside.
RF parts are especially likely to be under-rated. Like a 2 volt rated
schottly detector diode that starts to leak at 7. Or RF amp parts that
actually run at 2x rated max voltage in normal use.
Probably because it's common in RF to end up with the part being
subjected to voltages double its normal supply rail figure.
When I use RF parts in time domain/pulse applications, I have to make up
my own rules.
It's rare to get even basic DC curves on RF parts. The data sheets say, literally, adjust the bias until it works. Or AC couple in and out and
don't ask questions about "volts". Which opens up the possibility of
novel biasing schemes.
GaN fets are interesting. As are mosfets that avalanche at some
unspecified voltage.
A bit of air flow can really change things. I assume that most specs
are based on still air.
I've seen a few parts that were unreliable within their abs max specs
and needed to be derated from there.
Blow up some parts. It's fun.
Best fun you can have with your clothes on as they say.
Clothes on and safety goggles.
Presumably, one should feel comfortable using a device at the
published operating temperature extremes "forever".
But, what sort of derating likely went into that specification
in the first place? Sad another way, how much *beyond* those
limits might want suspect you could operate the device?
On Mon, 3 Jun 2024 07:52:58 -0700, Don Y <blockedofcourse@foo.invalid>
wrote:
Presumably, one should feel comfortable using a device at the
published operating temperature extremes "forever".
But, what sort of derating likely went into that specification
in the first place? Sad another way, how much *beyond* those
limits might want suspect you could operate the device?
There are two basic limits to operating environment temperatures.
Junction temperature limits are usually proscribed below book
Tjmax for an agreed mtbf. Sometimes the environmental limits
can be extended under reduced performance guidelines, without
exceeding agreed Tj limits.
For a whole product, there's usually other component limiting factors
that occur first - electrolytic and film capacitors, insulation system ratings and surface touch restrictions.
Performance is measured with these specified limits in mind.
or not.
On 6/6/2024 10:45 AM, legg wrote:
On Mon, 3 Jun 2024 07:52:58 -0700, Don Y <blockedofcourse@foo.invalid>
wrote:
Presumably, one should feel comfortable using a device at the
published operating temperature extremes "forever".
But, what sort of derating likely went into that specification
in the first place? Sad another way, how much *beyond* those
limits might want suspect you could operate the device?
There are two basic limits to operating environment temperatures.
Junction temperature limits are usually proscribed below book
Tjmax for an agreed mtbf. Sometimes the environmental limits
can be extended under reduced performance guidelines, without
exceeding agreed Tj limits.
For a whole product, there's usually other component limiting factors
that occur first - electrolytic and film capacitors, insulation system
ratings and surface touch restrictions.
Performance is measured with these specified limits in mind.
or not.
Yes, but is it (measured)? Or, actively designed with as a target?
Or, do you just use rules of thumb knowing that the typical *operating* >environment is likely to be X and chose components specified for Y > X
(but not necessarily Y >> X)?
Note this iPhone claims a max operating of 93F and storage of 113F.
It is now 108F outside -- does that mean I can't use it outdoors?
And, when the temperature climbs to 115, I'll have to set it in an
ice bath? (I'm being facetious, of course).
I suspect there isn't a place in the lower 48 that doesn't
see ambient temperatures above 93F at least part of the year.
And, Apple isn't a garage shop with few design/test resources at
its disposal.
So, clearly there is margin in these specifications. Whether it
is intended -- and to what extent -- is my point.
When designing for industrial/commercial applications, we were always >extremely careful to *ensure* our products would operate in the temperature >ranges (and other environmental factors) that we specified. A fisherman
out on the North Atlantic would be miffed if his kit stopped working
because it was too cold or too hot (or, too much salt spray). A craftsman >would be annoyed if the tip of his screwdriver sheared off from "excessive" >torque.
Similarly, a factory floor can't shut down because it's an unusually
warm day in the shop...
Consumer kit *seems* to have a far more cavalier attitude towards
these things. And, one that doesn't really hold up to close inspection >(e.g., the iPhone).
Commercial considerations of free enterprise have always pushed
human behaviour towards banditry, so what can I tell you?
On 6/7/2024 6:35 AM, legg wrote:
Commercial considerations of free enterprise have always pushed
human behaviour towards banditry, so what can I tell you?
But banditry would suggest taking advantage of the customer.
This is the opposite; the customer gets *more* performance
than the stated capabilities.
But, no way to know HOW MUCH more!
On Fri, 7 Jun 2024 12:45:24 -0700, Don Y <blockedofcourse@foo.invalid>
wrote:
On 6/7/2024 6:35 AM, legg wrote:
Commercial considerations of free enterprise have always pushed
human behaviour towards banditry, so what can I tell you?
But banditry would suggest taking advantage of the customer.
This is the opposite; the customer gets *more* performance
than the stated capabilities.
But, no way to know HOW MUCH more!
What exactly IS your concern?
On Thu, 6 Jun 2024 14:01:04 -0700, Don Y <blockedofcourse@foo.invalid>
wrote:
On 6/6/2024 10:45 AM, legg wrote:The guidelines are derived from empirical data and accelerating
On Mon, 3 Jun 2024 07:52:58 -0700, Don Y <blockedofcourse@foo.invalid>
wrote:
Presumably, one should feel comfortable using a device at the
published operating temperature extremes "forever".
But, what sort of derating likely went into that specification
in the first place? Sad another way, how much *beyond* those
limits might want suspect you could operate the device?
There are two basic limits to operating environment temperatures.
Junction temperature limits are usually proscribed below book
Tjmax for an agreed mtbf. Sometimes the environmental limits
can be extended under reduced performance guidelines, without
exceeding agreed Tj limits.
For a whole product, there's usually other component limiting factors
that occur first - electrolytic and film capacitors, insulation system
ratings and surface touch restrictions.
Performance is measured with these specified limits in mind.
or not.
Yes, but is it (measured)? Or, actively designed with as a target?
Or, do you just use rules of thumb knowing that the typical *operating* >>environment is likely to be X and chose components specified for Y > X
(but not necessarily Y >> X)?
Note this iPhone claims a max operating of 93F and storage of 113F.
It is now 108F outside -- does that mean I can't use it outdoors?
And, when the temperature climbs to 115, I'll have to set it in an
ice bath? (I'm being facetious, of course).
I suspect there isn't a place in the lower 48 that doesn't
see ambient temperatures above 93F at least part of the year.
And, Apple isn't a garage shop with few design/test resources at
its disposal.
So, clearly there is margin in these specifications. Whether it
is intended -- and to what extent -- is my point.
When designing for industrial/commercial applications, we were always >>extremely careful to *ensure* our products would operate in the temperature >>ranges (and other environmental factors) that we specified. A fisherman >>out on the North Atlantic would be miffed if his kit stopped working >>because it was too cold or too hot (or, too much salt spray). A craftsman >>would be annoyed if the tip of his screwdriver sheared off from "excessive" >>torque.
Similarly, a factory floor can't shut down because it's an unusually
warm day in the shop...
Consumer kit *seems* to have a far more cavalier attitude towards
these things. And, one that doesn't really hold up to close inspection >>(e.g., the iPhone).
factors are determined. The arrhenius equation comes to mind.
Predictors determine the design guidelines, but, yes, varying
degrees of physical testing is a standard element in design and
product verification.
Commercial considerations of free enterprise have always pushed
human behaviour towards banditry, so what can I tell you?
RL
On 6/7/2024 2:59 PM, legg wrote:
On Fri, 7 Jun 2024 12:45:24 -0700, Don Y <blockedofcourse@foo.invalid>
wrote:
On 6/7/2024 6:35 AM, legg wrote:
Commercial considerations of free enterprise have always pushed
human behaviour towards banditry, so what can I tell you?
But banditry would suggest taking advantage of the customer.
This is the opposite; the customer gets *more* performance
than the stated capabilities.
But, no way to know HOW MUCH more!
What exactly IS your concern?
I want too know how much MORE than the published/unpublished operating
limits one can reasonably expect from a piece of kit -- given that
these limits don't seem to TRULY represent "maxima".
We have a general idea of the types of components used in these
things and realize that their operating limits usually exceed the
published limits for the composite device -- often by a lot!
This suggests (to me) that the published limits aren't backed by
"real" engineering or stress testing. But, rather, likely arise
from marketing specs... someone making a SWAG as to how customers
will LIKELY use the devices and not what their actual design limits
happen to be.
[Given that using ANYTHING beyond its operating limits leaves you
without a leg to stand on, it would be nice to have some idea as to
what a reasonable expectation for those limits might be, despite
the "fluff" on the spec sheet. E.g., I would be really pressing my
luck to use something at 80C in that most components would likely
not be specified at those extremes. But, 55C for a 50C-specified
device? 60C?]
On Fri, 07 Jun 2024 09:35:38 -0400, legg <legg@nospam.magma.ca> wrote:
On Thu, 6 Jun 2024 14:01:04 -0700, Don Y <blockedofcourse@foo.invalid> >>wrote:
On 6/6/2024 10:45 AM, legg wrote:The guidelines are derived from empirical data and accelerating
On Mon, 3 Jun 2024 07:52:58 -0700, Don Y <blockedofcourse@foo.invalid> >>>> wrote:
Presumably, one should feel comfortable using a device at the
published operating temperature extremes "forever".
But, what sort of derating likely went into that specification
in the first place? Sad another way, how much *beyond* those
limits might want suspect you could operate the device?
There are two basic limits to operating environment temperatures.
Junction temperature limits are usually proscribed below book
Tjmax for an agreed mtbf. Sometimes the environmental limits
can be extended under reduced performance guidelines, without
exceeding agreed Tj limits.
For a whole product, there's usually other component limiting factors
that occur first - electrolytic and film capacitors, insulation system >>>> ratings and surface touch restrictions.
Performance is measured with these specified limits in mind.
or not.
Yes, but is it (measured)? Or, actively designed with as a target?
Or, do you just use rules of thumb knowing that the typical *operating* >>>environment is likely to be X and chose components specified for Y > X >>>(but not necessarily Y >> X)?
Note this iPhone claims a max operating of 93F and storage of 113F.
It is now 108F outside -- does that mean I can't use it outdoors?
And, when the temperature climbs to 115, I'll have to set it in an
ice bath? (I'm being facetious, of course).
I suspect there isn't a place in the lower 48 that doesn't
see ambient temperatures above 93F at least part of the year.
And, Apple isn't a garage shop with few design/test resources at
its disposal.
So, clearly there is margin in these specifications. Whether it
is intended -- and to what extent -- is my point.
When designing for industrial/commercial applications, we were always >>>extremely careful to *ensure* our products would operate in the temperature >>>ranges (and other environmental factors) that we specified. A fisherman >>>out on the North Atlantic would be miffed if his kit stopped working >>>because it was too cold or too hot (or, too much salt spray). A craftsman >>>would be annoyed if the tip of his screwdriver sheared off from "excessive" >>>torque.
Similarly, a factory floor can't shut down because it's an unusually
warm day in the shop...
Consumer kit *seems* to have a far more cavalier attitude towards
these things. And, one that doesn't really hold up to close inspection >>>(e.g., the iPhone).
factors are determined. The arrhenius equation comes to mind.
Predictors determine the design guidelines, but, yes, varying
degrees of physical testing is a standard element in design and
product verification.
Commercial considerations of free enterprise have always pushed
human behaviour towards banditry, so what can I tell you?
RL
That's entirely wrong. Whether you make spears or helicopters, you
need repeat business.
Communist thugs are the genocidal bandits. They have a captive market
and no competition.
On 6/7/2024 2:59 PM, legg wrote:
On Fri, 7 Jun 2024 12:45:24 -0700, Don Y <blockedofcourse@foo.invalid>
wrote:
On 6/7/2024 6:35 AM, legg wrote:
Commercial considerations of free enterprise have always pushed
human behaviour towards banditry, so what can I tell you?
But banditry would suggest taking advantage of the customer.
This is the opposite; the customer gets *more* performance
than the stated capabilities.
But, no way to know HOW MUCH more!
What exactly IS your concern?
I want too know how much MORE than the published/unpublished operating
limits one can reasonably expect from a piece of kit -- given that
these limits don't seem to TRULY represent "maxima".
We have a general idea of the types of components used in these
things and realize that their operating limits usually exceed the
published limits for the composite device -- often by a lot!
This suggests (to me) that the published limits aren't backed by
"real" engineering or stress testing. But, rather, likely arise
from marketing specs... someone making a SWAG as to how customers
will LIKELY use the devices and not what their actual design limits
happen to be.
[Given that using ANYTHING beyond its operating limits leaves you
without a leg to stand on, it would be nice to have some idea as to
what a reasonable expectation for those limits might be, despite
the "fluff" on the spec sheet. E.g., I would be really pressing my
luck to use something at 80C in that most components would likely
not be specified at those extremes. But, 55C for a 50C-specified
device? 60C?]
[Given that using ANYTHING beyond its operating limits leaves you
without a leg to stand on, it would be nice to have some idea as to
what a reasonable expectation for those limits might be, despite
the "fluff" on the spec sheet. E.g., I would be really pressing my
luck to use something at 80C in that most components would likely
not be specified at those extremes. But, 55C for a 50C-specified
device? 60C?]
Given that you expect to get what's promised when you pay for it,
outside of banditry, I only expect performance and a reasonable
service life.
I often kick mysellf in the head when I realize that shortcomings
in product performance were actually predicted in the written
specification - that the performance that I was expecting was not
only outside published spec, but might not be physically
possible, using current materials and techniques.
On Fri, 07 Jun 2024 15:19:50 -0700, john larkin <jl@650pot.com> wrote:
On Fri, 07 Jun 2024 09:35:38 -0400, legg <legg@nospam.magma.ca> wrote:
On Thu, 6 Jun 2024 14:01:04 -0700, Don Y <blockedofcourse@foo.invalid> >>>wrote:
On 6/6/2024 10:45 AM, legg wrote:The guidelines are derived from empirical data and accelerating
On Mon, 3 Jun 2024 07:52:58 -0700, Don Y <blockedofcourse@foo.invalid> >>>>> wrote:
Presumably, one should feel comfortable using a device at the
published operating temperature extremes "forever".
But, what sort of derating likely went into that specification
in the first place? Sad another way, how much *beyond* those
limits might want suspect you could operate the device?
There are two basic limits to operating environment temperatures.
Junction temperature limits are usually proscribed below book
Tjmax for an agreed mtbf. Sometimes the environmental limits
can be extended under reduced performance guidelines, without
exceeding agreed Tj limits.
For a whole product, there's usually other component limiting factors >>>>> that occur first - electrolytic and film capacitors, insulation system >>>>> ratings and surface touch restrictions.
Performance is measured with these specified limits in mind.
or not.
Yes, but is it (measured)? Or, actively designed with as a target?
Or, do you just use rules of thumb knowing that the typical *operating* >>>>environment is likely to be X and chose components specified for Y > X >>>>(but not necessarily Y >> X)?
Note this iPhone claims a max operating of 93F and storage of 113F.
It is now 108F outside -- does that mean I can't use it outdoors?
And, when the temperature climbs to 115, I'll have to set it in an
ice bath? (I'm being facetious, of course).
I suspect there isn't a place in the lower 48 that doesn't
see ambient temperatures above 93F at least part of the year.
And, Apple isn't a garage shop with few design/test resources at
its disposal.
So, clearly there is margin in these specifications. Whether it
is intended -- and to what extent -- is my point.
When designing for industrial/commercial applications, we were always >>>>extremely careful to *ensure* our products would operate in the temperature >>>>ranges (and other environmental factors) that we specified. A fisherman >>>>out on the North Atlantic would be miffed if his kit stopped working >>>>because it was too cold or too hot (or, too much salt spray). A craftsman >>>>would be annoyed if the tip of his screwdriver sheared off from "excessive" >>>>torque.
Similarly, a factory floor can't shut down because it's an unusually >>>>warm day in the shop...
Consumer kit *seems* to have a far more cavalier attitude towards
these things. And, one that doesn't really hold up to close inspection >>>>(e.g., the iPhone).
factors are determined. The arrhenius equation comes to mind.
Predictors determine the design guidelines, but, yes, varying
degrees of physical testing is a standard element in design and
product verification.
Commercial considerations of free enterprise have always pushed
human behaviour towards banditry, so what can I tell you?
RL
That's entirely wrong. Whether you make spears or helicopters, you
need repeat business.
Tell it to the bandits. There are plenty of suckers out there and >paper/internet bumph easily generated to suit them.
Communist thugs are the genocidal bandits. They have a captive market
and no competition.
Compared to the large-scale kleptocracies that replaced them? . . .
On 6/7/2024 9:25 PM, legg wrote:
[Given that using ANYTHING beyond its operating limits leaves you
without a leg to stand on, it would be nice to have some idea as to
what a reasonable expectation for those limits might be, despite
the "fluff" on the spec sheet. E.g., I would be really pressing my
luck to use something at 80C in that most components would likely
not be specified at those extremes. But, 55C for a 50C-specified
device? 60C?]
Given that you expect to get what's promised when you pay for it,
outside of banditry, I only expect performance and a reasonable
service life.
But performance is only formally defined within the "operating conditions". And, many bits of consumer kit don't even specify these!
I often kick mysellf in the head when I realize that shortcomings
in product performance were actually predicted in the written
specification - that the performance that I was expecting was not
only outside published spec, but might not be physically
possible, using current materials and techniques.
Would you expect a cell phone to operate in the same nominal environments that a human being would encounter in their normal living? If it FAILED
to operate "above 93F" (which is likely most of the lower 48, at some
portion of the day, lately), you'd likely be looking for another device
as you would always have to be in an air conditioned environment to make
that guarantee.
[And, if *storage* above 113 was contraindicated, how many could leave
it in an unattended/garaged car? You KNOW that you can't store *ice*
above 0C and, thus, don't!]
So, what value writing those limits on the formal product specification? Obviously (as we haven't seen class-action lawsuits from folks claiming
their thousand dollar phones don't work in the Summer months) the devices work beyond their stated operational limits.
Is the limit published solely to give the manufacturer a legal "out"
if large numbers of units suddenly DO start failing? While that may avoid
a lawsuit, today, how likely would it be to endear future purchasers to
a product if such a constraint became well-known?
Said another way, why not just *say* "25C" and hope customers are just
as oblivious of the actual declaration?
*Or*, say 42.1C after a careful analysis of the design and its actual operating temperature limits?
[I just don't see value in these numbers as they stand, currently]
I often kick mysellf in the head when I realize that shortcomings
in product performance were actually predicted in the written
specification - that the performance that I was expecting was not
only outside published spec, but might not be physically
possible, using current materials and techniques.
Would you expect a cell phone to operate in the same nominal environments
that a human being would encounter in their normal living? If it FAILED
to operate "above 93F" (which is likely most of the lower 48, at some
portion of the day, lately), you'd likely be looking for another device
as you would always have to be in an air conditioned environment to make
that guarantee.
I used to be in the iPhone design team. At the time we used a 40 deg C as the maximum ambient temperature.
As part of the development we would run a "thermal virus" software to cause the
CPU to dissipate an approximation for the maximum possible.
Under those conditions the internal temperature could get to the 70 deg C region. If excessive temperatures were reached the CPU would be throttled to avoid damage.
I was working on the display/touch hardware; LCD displays stop working at about
75 deg C (they just turn black).
Since the display was within a couple mm of
the CPU there was not margin.
Under less stressed conditions the internal temperature was much lower.
I suspect that the battery is probably the most sensitive item for storage temperature while not operating, especially if fully charged.
On Sat, 08 Jun 2024 00:29:20 -0400, legg <legg@nospam.magma.ca> wrote:
On Fri, 07 Jun 2024 15:19:50 -0700, john larkin <jl@650pot.com> wrote:
On Fri, 07 Jun 2024 09:35:38 -0400, legg <legg@nospam.magma.ca> wrote:
On Thu, 6 Jun 2024 14:01:04 -0700, Don Y <blockedofcourse@foo.invalid> >>>>wrote:
On 6/6/2024 10:45 AM, legg wrote:The guidelines are derived from empirical data and accelerating
On Mon, 3 Jun 2024 07:52:58 -0700, Don Y <blockedofcourse@foo.invalid> >>>>>> wrote:
Presumably, one should feel comfortable using a device at the
published operating temperature extremes "forever".
But, what sort of derating likely went into that specification
in the first place? Sad another way, how much *beyond* those
limits might want suspect you could operate the device?
There are two basic limits to operating environment temperatures.
Junction temperature limits are usually proscribed below book
Tjmax for an agreed mtbf. Sometimes the environmental limits
can be extended under reduced performance guidelines, without
exceeding agreed Tj limits.
For a whole product, there's usually other component limiting factors >>>>>> that occur first - electrolytic and film capacitors, insulation system >>>>>> ratings and surface touch restrictions.
Performance is measured with these specified limits in mind.
or not.
Yes, but is it (measured)? Or, actively designed with as a target?
Or, do you just use rules of thumb knowing that the typical *operating* >>>>>environment is likely to be X and chose components specified for Y > X >>>>>(but not necessarily Y >> X)?
Note this iPhone claims a max operating of 93F and storage of 113F. >>>>>It is now 108F outside -- does that mean I can't use it outdoors? >>>>>And, when the temperature climbs to 115, I'll have to set it in an >>>>>ice bath? (I'm being facetious, of course).
I suspect there isn't a place in the lower 48 that doesn't
see ambient temperatures above 93F at least part of the year.
And, Apple isn't a garage shop with few design/test resources at
its disposal.
So, clearly there is margin in these specifications. Whether it
is intended -- and to what extent -- is my point.
When designing for industrial/commercial applications, we were always >>>>>extremely careful to *ensure* our products would operate in the temperature
ranges (and other environmental factors) that we specified. A fisherman >>>>>out on the North Atlantic would be miffed if his kit stopped working >>>>>because it was too cold or too hot (or, too much salt spray). A craftsman >>>>>would be annoyed if the tip of his screwdriver sheared off from "excessive"
torque.
Similarly, a factory floor can't shut down because it's an unusually >>>>>warm day in the shop...
Consumer kit *seems* to have a far more cavalier attitude towards >>>>>these things. And, one that doesn't really hold up to close inspection >>>>>(e.g., the iPhone).
factors are determined. The arrhenius equation comes to mind.
Predictors determine the design guidelines, but, yes, varying
degrees of physical testing is a standard element in design and
product verification.
Commercial considerations of free enterprise have always pushed
human behaviour towards banditry, so what can I tell you?
RL
That's entirely wrong. Whether you make spears or helicopters, you
need repeat business.
Tell it to the bandits. There are plenty of suckers out there and >>paper/internet bumph easily generated to suit them.
You can buy Sony or cheap no-name Chinese junk. Your choice. Would you
prefer to not have a choice?
Communist thugs are the genocidal bandits. They have a captive market
and no competition.
Compared to the large-scale kleptocracies that replaced them? . . .
The US and Europe have antitrust laws that pretty well ensure multiple >suppliers and competition. The real kleptocracy, in the USA or in
Russia or in China, is the government.
If you don 't want to buy a car from Honda, GM, Ford, Toyota, Kia,
Tesla, VW, or BMW, walk in the rain and snow like most of your
ancestors did. Few of our ancestors could afford a horse.
On Fri, 07 Jun 2024 09:35:38 -0400, legg <legg@nospam.magma.ca> wrote:
On Thu, 6 Jun 2024 14:01:04 -0700, Don Y <blockedofcourse@foo.invalid> >>wrote:
On 6/6/2024 10:45 AM, legg wrote:The guidelines are derived from empirical data and accelerating
On Mon, 3 Jun 2024 07:52:58 -0700, Don Y <blockedofcourse@foo.invalid> >>>> wrote:
Presumably, one should feel comfortable using a device at the
published operating temperature extremes "forever".
But, what sort of derating likely went into that specification
in the first place? Sad another way, how much *beyond* those
limits might want suspect you could operate the device?
There are two basic limits to operating environment temperatures.
Junction temperature limits are usually proscribed below book
Tjmax for an agreed mtbf. Sometimes the environmental limits
can be extended under reduced performance guidelines, without
exceeding agreed Tj limits.
For a whole product, there's usually other component limiting factors
that occur first - electrolytic and film capacitors, insulation system >>>> ratings and surface touch restrictions.
Performance is measured with these specified limits in mind.
or not.
Yes, but is it (measured)? Or, actively designed with as a target?
Or, do you just use rules of thumb knowing that the typical *operating* >>>environment is likely to be X and chose components specified for Y > X >>>(but not necessarily Y >> X)?
Note this iPhone claims a max operating of 93F and storage of 113F.
It is now 108F outside -- does that mean I can't use it outdoors?
And, when the temperature climbs to 115, I'll have to set it in an
ice bath? (I'm being facetious, of course).
I suspect there isn't a place in the lower 48 that doesn't
see ambient temperatures above 93F at least part of the year.
And, Apple isn't a garage shop with few design/test resources at
its disposal.
So, clearly there is margin in these specifications. Whether it
is intended -- and to what extent -- is my point.
When designing for industrial/commercial applications, we were always >>>extremely careful to *ensure* our products would operate in the temperature >>>ranges (and other environmental factors) that we specified. A fisherman >>>out on the North Atlantic would be miffed if his kit stopped working >>>because it was too cold or too hot (or, too much salt spray). A craftsman >>>would be annoyed if the tip of his screwdriver sheared off from "excessive" >>>torque.
Similarly, a factory floor can't shut down because it's an unusually
warm day in the shop...
Consumer kit *seems* to have a far more cavalier attitude towards
these things. And, one that doesn't really hold up to close inspection >>>(e.g., the iPhone).
factors are determined. The arrhenius equation comes to mind.
Predictors determine the design guidelines, but, yes, varying
degrees of physical testing is a standard element in design and
product verification.
Commercial considerations of free enterprise have always pushed
human behaviour towards banditry, so what can I tell you?
RL
That's entirely wrong. Whether you make spears or helicopters, you
need repeat business.
Communist thugs are the genocidal bandits. They have a captive market
and no competition.
On 6/8/2024 12:03 PM, KevinJ93 wrote:
I often kick mysellf in the head when I realize that shortcomings
in product performance were actually predicted in the written
specification - that the performance that I was expecting was not
only outside published spec, but might not be physically
possible, using current materials and techniques.
Would you expect a cell phone to operate in the same nominal environments >>> that a human being would encounter in their normal living? If it FAILED >>> to operate "above 93F" (which is likely most of the lower 48, at some
portion of the day, lately), you'd likely be looking for another device
as you would always have to be in an air conditioned environment to make >>> that guarantee.
I used to be in the iPhone design team. At the time we used a 40 deg C as the
maximum ambient temperature.
It's that, here, now (103F) -- and another 5-10 degrees expected before
temps start back down. And, I imagine a few million people are experiencing >that same sort of temperature. If 20% have iPhones, that's a shitload of >devices operating at or above their design maxima.
Where did the "40" come from? Why not 41C (was that not "round enough"?)
Or, "100F"? I.e., was it arrived at by deliberate thought or just picked
out of the air as "good enough"?
As part of the development we would run a "thermal virus" software to cause the
CPU to dissipate an approximation for the maximum possible.
Under those conditions the internal temperature could get to the 70 deg C
region. If excessive temperatures were reached the CPU would be throttled to >> avoid damage.
Makes sense. But, has limits to its applicability. I.e., if the CPU >couldn't support the load of running the cellular radio, then you've >prevented damage but still rendered the phone inoperative.
I was working on the display/touch hardware; LCD displays stop working at about
75 deg C (they just turn black)
Yes. The technology has lots of environmental limits. And, too cold
and it gets sluggish (not a good thing for an AC device).
Since the display was within a couple mm of
the CPU there was not margin.
Under less stressed conditions the internal temperature was much lower.
I suspect that the battery is probably the most sensitive item for storage >> temperature while not operating, especially if fully charged.
And the battery's failure mode can be spectacular. So, do they
rely on the printed specifications to bail them out of any liability >lawsuits?
Note that you don't tend to see different "grades" of consumer kit
as you would encounter in commercial/industrial markets -- where
the consumer can buy an option/upgrade/upsell to address a market
that he feels more typically reflects his usage.
How many consumers actually are aware of these parameters for
the kit they've bought (often at very dear prices)?
When we were last looking at vehicles, we noticed many of the
"front-facing technology" would throw errors, before you even
made it onto the road for a test drive. "Oh, the electronics
are overheating from being out in the sun..." "WTF? So, can
I only drive at night? And, how many kilobucks for this bit
of kit??"
Would you expect a cell phone to operate in the same nominal environments >>>> that a human being would encounter in their normal living? If it FAILED >>>> to operate "above 93F" (which is likely most of the lower 48, at some
portion of the day, lately), you'd likely be looking for another device >>>> as you would always have to be in an air conditioned environment to make >>>> that guarantee.
I used to be in the iPhone design team. At the time we used a 40 deg C as the
maximum ambient temperature.
It's that, here, now (103F) -- and another 5-10 degrees expected before
temps start back down. And, I imagine a few million people are experiencing >> that same sort of temperature. If 20% have iPhones, that's a shitload of
devices operating at or above their design maxima.
Where did the "40" come from? Why not 41C (was that not "round enough"?)
Or, "100F"? I.e., was it arrived at by deliberate thought or just picked
out of the air as "good enough"?
40C is the ambient temperature where public health safety warnings are
issued in most jurisdictions. Schools will cancel track meets etc.
Some ammend that to wet bulb temperatures, which can be reached in as
low as 36C environment.Don't confuse it with the Fahrenheit scale.
As part of the development we would run a "thermal virus" software to cause the
CPU to dissipate an approximation for the maximum possible.
Under those conditions the internal temperature could get to the 70 deg C >>> region. If excessive temperatures were reached the CPU would be throttled to
avoid damage.
Makes sense. But, has limits to its applicability. I.e., if the CPU
couldn't support the load of running the cellular radio, then you've
prevented damage but still rendered the phone inoperative.
I was working on the display/touch hardware; LCD displays stop working at about
75 deg C (they just turn black)
You'd probably find that surface touch temperature limits are exceeded
before that - screens having direct access to the external
environment.
Yes. The technology has lots of environmental limits. And, too cold
and it gets sluggish (not a good thing for an AC device).
LCD screens also become unreadable at ~ -20C. Again - don't confuse it
with the Fahrenheit scale.
Since the display was within a couple mm of
the CPU there was not margin.
Under less stressed conditions the internal temperature was much lower.
I suspect that the battery is probably the most sensitive item for storage >>> temperature while not operating, especially if fully charged.
And the battery's failure mode can be spectacular. So, do they
rely on the printed specifications to bail them out of any liability
lawsuits?
He's talking about aging, loss of capacity and charging voltage
tolernce restrictions. Lithium battery 'cook-off' temperatures
are much higher.
Note that you don't tend to see different "grades" of consumer kit
as you would encounter in commercial/industrial markets -- where
the consumer can buy an option/upgrade/upsell to address a market
that he feels more typically reflects his usage.
How many consumers actually are aware of these parameters for
the kit they've bought (often at very dear prices)?
Industrial grade components and equipment are designed for
higher operating ambients - but equipment designed for personal
(hand-held or pocket) use assume the limits for human physical
comfort and safety.
When we were last looking at vehicles, we noticed many of the
"front-facing technology" would throw errors, before you even
made it onto the road for a test drive. "Oh, the electronics
are overheating from being out in the sun..." "WTF? So, can
I only drive at night? And, how many kilobucks for this bit
of kit??"
Vehicular operating environmental limits differ from consumer
equipment standards.
What's your actual problem?
On 6/12/2024 9:13 AM, legg wrote:
Would you expect a cell phone to operate in the same nominal environments >>>>> that a human being would encounter in their normal living? If it FAILED >>>>> to operate "above 93F" (which is likely most of the lower 48, at some >>>>> portion of the day, lately), you'd likely be looking for another device >>>>> as you would always have to be in an air conditioned environment to make >>>>> that guarantee.
I used to be in the iPhone design team. At the time we used a 40 deg C as the
maximum ambient temperature.
It's that, here, now (103F) -- and another 5-10 degrees expected before
temps start back down. And, I imagine a few million people are experiencing
that same sort of temperature. If 20% have iPhones, that's a shitload of >>> devices operating at or above their design maxima.
Where did the "40" come from? Why not 41C (was that not "round enough"?) >>> Or, "100F"? I.e., was it arrived at by deliberate thought or just picked >>> out of the air as "good enough"?
40C is the ambient temperature where public health safety warnings are
issued in most jurisdictions. Schools will cancel track meets etc.
Some ammend that to wet bulb temperatures, which can be reached in as
low as 36C environment.Don't confuse it with the Fahrenheit scale.
I'm not "confusing it" -- rather, deliberately using "100" as a "nice round >number" (note my comment re: 41C vs 40C) Is it just "coincidence" that
the "safety warnings" are issued at 40 and not 39? Or, 41? Is there >something "magical" about "40" -- other than it ends in a '0'?
It's been above 100F (38C) for 16 days, already. People are still working >their normal outdoor jobs, looking at cars on dealer lots, walking 100 yards >across uncovered parking lots to gain entry to stores, etc.
Are phones NOT expected to work in these environments? (Gee, I wanted to >telephone emergency services to get help for my buddy who collapsed in
the heat but it was too hot for my phone to make the call)
We expect cars to continue to operate in those temperatures. What's the >criteria that we use to determine what should and shouldn't be expected
to remain operational?
And, how do these limits differ from the (somewhat arbitrary) figures
that we publish as specifications?
As part of the development we would run a "thermal virus" software to cause the
CPU to dissipate an approximation for the maximum possible.
Under those conditions the internal temperature could get to the 70 deg C >>>> region. If excessive temperatures were reached the CPU would be throttled to
avoid damage.
Makes sense. But, has limits to its applicability. I.e., if the CPU
couldn't support the load of running the cellular radio, then you've
prevented damage but still rendered the phone inoperative.
I was working on the display/touch hardware; LCD displays stop working at about
75 deg C (they just turn black)
You'd probably find that surface touch temperature limits are exceeded
before that - screens having direct access to the external
environment.
You don't need to use a bare finger to activate a screen. And, with most >phones, can use voice dialing.
Yes. The technology has lots of environmental limits. And, too cold
and it gets sluggish (not a good thing for an AC device).
LCD screens also become unreadable at ~ -20C. Again - don't confuse it
with the Fahrenheit scale.
Since the display was within a couple mm of
the CPU there was not margin.
Under less stressed conditions the internal temperature was much lower. >>>>
I suspect that the battery is probably the most sensitive item for storage >>>> temperature while not operating, especially if fully charged.
And the battery's failure mode can be spectacular. So, do they
rely on the printed specifications to bail them out of any liability
lawsuits?
He's talking about aging, loss of capacity and charging voltage
tolernce restrictions. Lithium battery 'cook-off' temperatures
are much higher.
So, a battery stored 1C beyond that maximum storage temperature
is crap? Of course not. For *components*, we have graphs that
make these relationships more explicit. So, I can trade off
temperature vs. performance, etc.
For *devices*, we rely on a single number to express a limit
(operating or storage). It's fairly obvious that these
limits are not hard and fast and have fudge factors built in.
How large those are is up to the person designing the product and
writing the published specification.
Note that you don't tend to see different "grades" of consumer kit
as you would encounter in commercial/industrial markets -- where
the consumer can buy an option/upgrade/upsell to address a market
that he feels more typically reflects his usage.
How many consumers actually are aware of these parameters for
the kit they've bought (often at very dear prices)?
Industrial grade components and equipment are designed for
higher operating ambients - but equipment designed for personal
(hand-held or pocket) use assume the limits for human physical
comfort and safety.
But that's not true. Sit outside in 93F temperatures (the published
spec for the iPhones I researched) and you will neither be comfortable
nor safe. Why doesn't everything operate at 25C which is where we
tend to be most comfortable and feel most safe? Ans: because we
live in conditions that extend well above and below those limits.
I can recall being outdoors in -26F and +117F. I was much more
uncomfortable at -26F than at 117F (I was actually hauling 20T of
stone and, aside from the weight of the stone, more comfortable
than I'd been at 80F in New England)
So, what value writing a published specification limit that
you KNOW will be exceeded, REGULARLY? Are you looking for a
legal leg to stand on when the user tries to dial "911" and
the phone fails to perform as expected -- because it was 94F
at the time?
When we were last looking at vehicles, we noticed many of the
"front-facing technology" would throw errors, before you even
made it onto the road for a test drive. "Oh, the electronics
are overheating from being out in the sun..." "WTF? So, can
I only drive at night? And, how many kilobucks for this bit
of kit??"
Vehicular operating environmental limits differ from consumer
equipment standards.
But kit designed for the vehicle should be operable IN the
conditions that the vehicle is expected to experience, right?
Or, am I supposed to stand outside the vehicle until the
passenger compartment (which houses the kit in question) drops
to "human limits" (how do I start the vehicle to move it into
the shade? or, activate the air conditioning? will the air
conditioning sensors operate in those "above human" limits??)
What's your actual problem?
If I have a device that claims an operating (or storage) temperature range
of [X,Y] what is the ACTUAL operating range LIKELY *designed* into the device.
Ask yourself what YOUR design process is. Do you design something and
then put some numbers on it's operating range after the design is
complete? By measuring it's capabilities? By SWAG?
Do you write a target specification and then keep tweeking your
design to ensure that it continues to satisfy those constraints?
Do you then verify this, empirically? Or, do you say, "I've got
12 degrees of margin and the temperature rise in the enclosure
will never exceed 7 degrees so I rationalize that I am safe"?
Why do we derate other attributes of our designs (and components)?
Do we not also derate more general characteristics -- like operating >temperature (clearly this happens; the question is whether or not
there is a conscious effort made and what the criteria are besides
"this is how we EXPECT it to be used")
I specify the TIMEliness of my systems' responses. There's margin
in those figures. A customer can rely on my meeting them ALWAYS,
because I have addressed all of the (unlikely) issues that could
cause them to vary. I *design* to a tighter set of values and
derate that specification, deliberately, to give customers
confidence that they won't be operating at the bleeding edge
of the design *if* they use the published figures.
But, I know that my derated figures are adequate for the market
that I am serving. I don't make devices that aren't GUARANTEED
to be operable in the conditions that you WILL encounter.
Clearly, a phone that claims to operate to 93F is not designed
to operate in the temperature ranges that MOST customers encounter!
Yet, no one cautions them to avoid these phones.
[Repeat for the other examples I have given]
It's been above 100F (38C) for 16 days, already. People are still working their normal outdoor jobs, looking at cars on dealer lots, walking 100
yards
across uncovered parking lots to gain entry to stores, etc.
Are phones NOT expected to work in these environments? (Gee, I wanted to telephone emergency services to get help for my buddy who collapsed in
the heat but it was too hot for my phone to make the call)
We expect cars to continue to operate in those temperatures. What's the criteria that we use to determine what should and shouldn't be expected
to remain operational?
What's your actual problem?
If I have a device that claims an operating (or storage) temperature range >> of [X,Y] what is the ACTUAL operating range LIKELY *designed* into the device.
I think, at this stage, you're just being fractious.
I'm out of here.
On 6/12/24 12:26 PM, Don Y wrote:
<...>
It's been above 100F (38C) for 16 days, already. People are still working >> their normal outdoor jobs, looking at cars on dealer lots, walking 100 yards >> across uncovered parking lots to gain entry to stores, etc.
Are phones NOT expected to work in these environments? (Gee, I wanted to >> telephone emergency services to get help for my buddy who collapsed in
the heat but it was too hot for my phone to make the call)
The phones may not stop working but may not meet performance specifications. For example applications may not work as fast as at lower temperatures.
I've never heard of lower level software being compromised at high temperatures
so basic phone calls would be ok but action video games would run slower.
The ASICs I worked on had a -25C to +75C operating range. When the CPU was idle
the phone would be too hot to hold if the internals were at 75C.
We expect cars to continue to operate in those temperatures. What's the
criteria that we use to determine what should and shouldn't be expected
to remain operational?
Automotive devices that expect to be in the engine compartment are designed for
-40C to +125C or +150C.
On 6/13/2024 12:42 PM, KevinJ93 wrote:<...>
The idea of *carrying* a phone on my person is anathema to me. So, anyphones but
time
I take a phone out of the house, it sits in the car while I run my errands. After half an hour, the interior of the car exceeds 130F with certain surfaces
approaching 160F (seats are ~125F).
Yet, the phone operates.
Well beyond max operating *and* storage. (thus, "margin" -- just no way to put an actual figure on it, besides for one exemplar)
I've never heard of lower level software being compromised at high
temperatures so basic phone calls would be ok but action video games
would run slower.
The fact that the phone (and other exemplars) operates outside of its "operating range" confirms there is margin in the design. We know that. > But, no one seems to know *what* this margin is. (It's not just
almost all consumer kit -- excepting those for which NO operating/storage conditions are specified!)
This suggests that it is NOT a part of the design process but, rather, "whatever it is, it is".
If I tried to make a call and the phone was 160F -- because it sat in my
car for three hours in the sun -- would it work? Is there ANYONE at Apple who could answer that question?
We expect cars to continue to operate in those temperatures. What's the >>> criteria that we use to determine what should and shouldn't be expected
to remain operational?
Automotive devices that expect to be in the engine compartment are
designed for -40C to +125C or +150C.
The devices I mentioned are located in the *passenger* compartment.
What value an engine compartment that can't be *controlled* by devices
in the passenger compartment? :>
Will the GPS operate when the vehicle's interior reaches 160F? What about the roadside assistance feature? Backup camera? Will the electronics that govern the cycling of the air conditioning compressor function? Do you recall
ever hearing someone complain of the electronics in their vehicles NOT working
when they returned to their parked vehicle after work? ("margin")
The fact that the car manufacturers recognized these some devices WOULD
fail
(and added a variety of idiot lights on the dash to signify those failures) suggests they either couldn't make them operate over these extremes *or* couldn't AFFORD to make them operate over these extremes.
But, as a buyer looking to drop $50+K on a vehicle, what assurances do
you have that those systems (for which you are paying additional monies)
WILL operate when you are the vehicle's owner? If they won't operate
when the vehicle is sitting on the *dealer's* lot, will they operate when
the vehicle is sitting in the grocery store's lot? Your employer's lot? Your driveway? On the highway? (etc)
Vendors seem to treat *consumers* as ignorant dweebs; the same sorts of hand-waving wouldn't be tolerated by an industrial/commercial customer!
phones butI've never heard of lower level software being compromised at high
temperatures so basic phone calls would be ok but action video games would >>> run slower.
The fact that the phone (and other exemplars) operates outside of its
"operating range" confirms there is margin in the design. We know that. > >> But, no one seems to know *what* this margin is. (It's not just
almost all consumer kit -- excepting those for which NO operating/storage
conditions are specified!)
This suggests that it is NOT a part of the design process but, rather,
"whatever it is, it is".
If I tried to make a call and the phone was 160F -- because it sat in my
car for three hours in the sun -- would it work? Is there ANYONE at Apple >> who could answer that question?
160F is 71C so the the circuitry I was involved with could be guaranteed to work provided the internal temperature of the phone was not significantly higher than that 160F.
I believe similar limits would apply to other parts of the phone.
However if the internal temperature had been raised significantly by any internal power dissipation then all bets are off.
CPUs are especially challenging as they can dissipate 5-10 Watts at extremes -
there is no room for anything in the way of heat sinks or fans etc. The best they can do is to thermally couple them to the case.
The power amplifiers in the RF section are also significant heat generating items.
Your question has a multi-dimensional answer, it depends upon a host of other things including the recent usage of the phone.
A phone could be designed to guarantee operation at the temperatures you state
but that phone would certainly cost more, be physically larger, heavier etc. The current specifications have been accepted as adequate by the majority of customers. Probably there do exist ones with extended environmental specs for specialized applications such as the military where that is more important than
cost, weight, size etc.
If you want to improve the likelihood that your phone works when you need it -
don't leave it lying in sun. Even in a hot car some places are cooler than others.
We expect cars to continue to operate in those temperatures. What's the >>>> criteria that we use to determine what should and shouldn't be expected >>>> to remain operational?
Automotive devices that expect to be in the engine compartment are designed >>> for -40C to +125C or +150C.
The devices I mentioned are located in the *passenger* compartment.
What value an engine compartment that can't be *controlled* by devices
in the passenger compartment? :>
I've also worked in some aspects of automobile design and there were multiple environmental zones defined - the cabin being the most benign.
Probably parts there are specified to 105C. Although it can get pretty toasty at the top of the dashboard.
Will the GPS operate when the vehicle's interior reaches 160F? What about >> the roadside assistance feature? Backup camera? Will the electronics that
govern the cycling of the air conditioning compressor function? Do you recall
ever hearing someone complain of the electronics in their vehicles NOT working
when they returned to their parked vehicle after work? ("margin")
The temperature is not uniform in the car and often electronics are placed in areas where they won't reach the high temperatures you mention - in some of my
cars for example the electronics were under the seats or behind the glovebox.
The fact that the car manufacturers recognized these some devices WOULD fail >> (and added a variety of idiot lights on the dash to signify those failures) >> suggests they either couldn't make them operate over these extremes *or*
couldn't AFFORD to make them operate over these extremes.
But, as a buyer looking to drop $50+K on a vehicle, what assurances do
you have that those systems (for which you are paying additional monies)
WILL operate when you are the vehicle's owner? If they won't operate
when the vehicle is sitting on the *dealer's* lot, will they operate when
the vehicle is sitting in the grocery store's lot? Your employer's lot?
Your driveway? On the highway? (etc)
Modern cars are impressively reliable but they may not be guaranteed to operate
over the full gamut of environmental conditions and usage. They just have meet
the great majority of the customers' expectations.
Vendors seem to treat *consumers* as ignorant dweebs; the same sorts of
hand-waving wouldn't be tolerated by an industrial/commercial customer!
The market decides. Price is a dominant factor in vehicle sales.
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