Discussion:
Operating temperature derating
(too old to reply)
Don Y
2024-06-03 14:52:58 UTC
Permalink
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?
Phil Hobbs
2024-06-03 15:52:20 UTC
Permalink
Post by Don Y
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?
Varies by device and package, unfortunately.

For example, running a plastic package above its glass transition will make
the epoxy creep due to thermal expansion. There’s nothing much to make it
creep back again on cooling. Cycles of that will eventually create voids,
break bond wires, and so on.

Clive, previously Syd, will have lots more.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
john larkin
2024-06-03 16:03:10 UTC
Permalink
Post by Don Y
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.
Cursitor Doom
2024-06-03 21:41:59 UTC
Permalink
Post by john larkin
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.
Post by john larkin
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.
Post by john larkin
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.
john larkin
2024-06-03 22:05:58 UTC
Permalink
On Mon, 3 Jun 2024 21:41:59 -0000 (UTC), Cursitor Doom
Post by Cursitor Doom
Post by john larkin
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.
Post by john larkin
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.
Post by Cursitor Doom
Post by john larkin
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.
Cursitor Doom
2024-06-05 16:57:51 UTC
Permalink
Post by john larkin
On Mon, 3 Jun 2024 21:41:59 -0000 (UTC), Cursitor Doom
Post by Cursitor Doom
Post by john larkin
Post by Don Y
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.
Post by john larkin
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.
Yeah, RF biasing - well, everything to do with RF in fact is a blast,
isn't it? No wonder the guys at the cutting edge of it have always coined
the BIG BUCKS.
Post by john larkin
Post by Cursitor Doom
Post by john larkin
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.
Indeed. It's amazing how many decibels you can get out of even a 10uF
electrolytic.
Don Y
2024-06-04 13:22:15 UTC
Permalink
Post by Don Y
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!
Cursitor Doom
2024-06-05 16:59:54 UTC
Permalink
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
"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!
No wonder modern electronics - consumer electronics I mean - doesn't last
five minutes. :(
legg
2024-06-06 17:45:28 UTC
Permalink
Post by Don Y
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.

RL
Don Y
2024-06-06 21:01:04 UTC
Permalink
Post by legg
Post by Don Y
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).
legg
2024-06-07 13:35:38 UTC
Permalink
Post by Don Y
Post by legg
Post by Don Y
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).
The guidelines are derived from empirical data and accelerating
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
Don Y
2024-06-07 19:45:24 UTC
Permalink
Post by legg
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!
legg
2024-06-07 21:59:54 UTC
Permalink
Post by Don Y
Post by legg
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?

RL
Don Y
2024-06-07 22:16:49 UTC
Permalink
Post by legg
Post by Don Y
Post by legg
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?]
Phil Hobbs
2024-06-07 22:28:21 UTC
Permalink
Post by Don Y
Post by legg
Post by Don Y
Post by legg
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?]
We’ve had chipmaking folks here (including Miso, iirc) say that the abs max
ratings are primarily marketing driven, like most of the rest of the
datasheet.

You find out what your major customers are going to do with the part, and
derate it to match. That way you sell parts and still get to have a quiet
life.

Of course there are things like delamination, overvoltage and
electromigration that cause lifetime issues rather than prompt failures.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
legg
2024-06-08 04:25:25 UTC
Permalink
Post by Don Y
Post by legg
Post by Don Y
Post by legg
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 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.

RL
Don Y
2024-06-08 11:17:40 UTC
Permalink
Post by legg
Post by Don Y
[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!
Post by legg
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]
KevinJ93
2024-06-08 19:03:49 UTC
Permalink
Post by Don Y
Post by legg
Post by Don Y
[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!
Post by legg
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.

kw
Post by Don Y
[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]
Don Y
2024-06-08 20:35:16 UTC
Permalink
Post by Don Y
Post by legg
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??"
legg
2024-06-12 16:13:50 UTC
Permalink
Post by Don Y
Post by Don Y
Post by legg
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"?
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.
Post by Don Y
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.
Post by Don Y
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.
Post by Don Y
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.
Post by Don Y
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.
Post by Don Y
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?

RL
Don Y
2024-06-12 19:26:51 UTC
Permalink
Post by legg
Post by Don Y
Post by Don Y
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?
Post by legg
Post by Don Y
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.
Post by legg
Post by Don Y
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.
Post by Don Y
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.
Post by legg
Post by Don Y
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?
Post by legg
Post by Don Y
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??)
Post by legg
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]
legg
2024-06-13 11:51:59 UTC
Permalink
On Wed, 12 Jun 2024 12:26:51 -0700, Don Y
Post by Don Y
Post by legg
Post by Don Y
Post by Don Y
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 has something to do with the human body at reat, in the shade,
failing to be cooled by sweat in moving air at a certain temperature.
Cooling has then to be obtained by artificial means. It probably IS
a 'nice round number', as some are affected earlier than others.
A body will already be avoiding direct sun exposure with hats /
umbrellas, shade trees etc.
Post by Don Y
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)
Sorry to hear about your buddy. Senior citizens or health compromised
people have to take special care in the heat.

How do you know that was the problem with the phone?
What were the phone's symptoms?
Post by Don Y
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?
Already said - automotive component temperature limits are set by
other standards. That being said, it's a test of your vehicles
integrity to do hard work at elevated temperatures. For the benefit
of passengers, some attempt is made to keep the cabin below 40C.
Post by Don Y
And, how do these limits differ from the (somewhat arbitrary) figures
that we publish as specifications?
A company will have stated limits for a project in the earliest design
stages. They will use limits expected by their industry, unless there
are reasons to do otherwise. Stupidity would be a pretty bad reason.
Post by Don Y
Post by legg
Post by Don Y
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.
Are you serious? Touch temperature is the surface temperature in
contact with operator, usually the hand. If it's not meant to be
held, you can get away with visible surface temperature warnings.
Anything made to be touched doesn't get an exemption.
Post by Don Y
Post by legg
Post by Don Y
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.
Post by Don Y
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.
Post by legg
Post by Don Y
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.
Safety standards are pretty explicit w/r to operator environment.

Humans do not, in fact, operate well over any environmental extreme.
That's why we wear clothes; live in temperature-suitable dwellings,
don space suits etc.
Post by Don Y
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?
Commodities respond to market requirements.
Post by Don Y
Post by legg
Post by Don Y
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??)
Post by legg
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]
I think, at this stage, you're just being fractious.

I'm out of here.

RL
Don Y
2024-06-14 01:13:01 UTC
Permalink
Post by legg
Post by Don Y
Post by legg
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.
And I think you're just unable to answer the question. Don't feel bad;
I've asked this in two other places and have been met with similar
<mumbly> answers. No one seems to design "consumer kit" so there are no
REAL processes to describe. Commercial and Industrial designs are
handled much differently and more formally.

But, what the question HAS done is piqued interest in the *specifics*
of various bits of consumer kit; so, lots of examples of specific devices
with:
- UNspecified operating limits
- "fantasy" operating limits,
- limits that obviously have HUGE margins (e.g., the phone examples)
- *seemingly* well thought out limits (inferred by the wider range of
operating conditions that obviously exceed the sorts of conditions
they would likely experience... "temperatures never encountered on earth").

It seems like folks have suddenly become aware that they *don't* know
what the bits of kit that they've purchased CAN do and are now taking an
active interest in those figures.

It's educational to see which types of devices fit in each category as well
as which manufacturers.

But, still doesn't answer the question posed (as none of the designers
of these items are apparently available to shed specific light on their
design process/criteria)
Post by legg
I'm out of here.
KevinJ93
2024-06-13 19:42:47 UTC
Permalink
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.

kw
<...>
Don Y
2024-06-14 01:09:45 UTC
Permalink
<...>
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.
But, "applications may not work as fast" if multiple applications are running
or if you've installed some "service" that competes for resources. Where's
the disclaimer about that?

And, what's the caveat when the phone is being *operated* at a temperature
that exceeds its *storage* temperature? It's been hotter than 113 (iPhone
storage max) several times, here, already -- and summer doesn't officially
start for another week or so.

The idea of *carrying* a phone on my person is anathema to me. So, any 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 phones but
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?

My $40K electric wheelchair tells me to recharge the batteries in a certain
temperature range. But, doesn't tell me in what range of temperatures I can
OPERATE that chair! Surely this is important -- whether I live in Alaska or
Florida -- as a chair that won't move would leave me stranded!

I know I can operate (and "store" when not actively being operated) TVs on
the back porch despite the fact that the ambient climbs to well above 110.
Yet, the TVs don't tell me that this is possible.
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.
Of course you don't need to hold a phone to use it. My blind friends use
the voice interfaces to their phones (ear buds) -- leaving them in a fanny-pack
(or purse) so they can have their hands free for walking canes. That seems to
be increasingly common.

The fact that you design components for a 75C range suggests you expect the
phone's interior (at the die level) to approach that temperature. You
didn't, for example, design for 50C (and, in those sorts of volumes, you can
pick whatever point on the process/price/performance curve best suits your
needs/requirements instead of being constrained to "standard products")
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!
KevinJ93
2024-06-14 02:02:46 UTC
Permalink
<...>
The idea of *carrying* a phone on my person is anathema to me.  So, any
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)
Post by KevinJ93
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
phones but
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.

<...>
Post by KevinJ93
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.

kw
Don Y
2024-06-14 02:27:51 UTC
Permalink
Post by Don Y
Post by Don Y
Post by KevinJ93
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
phones but
Post by Don Y
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.
Of course! And, I am just using phones as an example as they are ubiquitous.
If you wander around your home, there are undoubtedly countless items that
all have real limits on their operation -- yet DETERMINING those would be
difficult (especially if you wanted to know REAL limits and not just
PUBLISHED limits)
Post by Don Y
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.
But that's exactly my point! The phone, AS DOCUMENTED, is considerably less
capable than it is, in reality! If it adhered to its published specifications,
I suspect a good many people would not use it -- because they routinely
encounter conditions that exceed those published for the phone.

SOMEONE (at Apple) knows this to be the case as they wouldn't market
a product that had millions of users complaining that their phones stopped
working in the summer (winter?) months.
Post by Don Y
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.
Of course. I've used this as an example of how WIDE the margin is in
the phone's design (*my* phone isn't an iPhone). I doubt many people
worry that the car interior may get too hot for their phones -- because
most people have never had a phone refuse to operate due to temperature
extremes!
Post by Don Y
Post by Don Y
Post by KevinJ93
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.
Dash gets up above 160. I've been amused that the ambient temperature
sensor is so acurate -- yet "sees" the heat reflected off the (180F)
pavement! Clearly some "engineering" at play, there.
Post by Don Y
Post by Don Y
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.
Yes, but over the course of an 8 hour "work day" (baking in the sun), I
suspect there are no "refuges" in the vehicle's interior. If the air
temperature is 113, then the car *will* climb to 113, over time.

(It will *drop* to 90 degrees after 10PM, tonight -- and today was relatively
cool -- just barely 100F)
Post by Don Y
Post by Don Y
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.
If you are charging a premium for certain technology features, it seems
like you would take steps to ensure that they *worked* in every market
in which they were offered.

As I said, I stepped behind the wheel of certain vehicles and watched
failure indicators illuminate in rapid succession: "That's because
the car is in the sun..." "Ah, OK. So, if I want those features, I
should keep the car in the shade? How do I do that on the roadways?"
Post by Don Y
Post by Don Y
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.
Price is a dominant factor in *many* decisions. Until performance
problems capture headlines. I'm sure the airlines that bought
Boeing products did so largely on price/performance/reputation issues...

Consumers tend to be largely ignorant of product capabilities and
limitations. They buy *features* -- without even guarantees that
those features work! And, because they often don't understand
what they have bought, they are never quite sure that a problem
is "theirs" or the *device's*

john larkin
2024-06-07 22:19:50 UTC
Permalink
Post by legg
Post by Don Y
Post by legg
Post by Don Y
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).
The guidelines are derived from empirical data and accelerating
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.
legg
2024-06-08 04:29:20 UTC
Permalink
Post by john larkin
Post by legg
Post by Don Y
Post by legg
Post by Don Y
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).
The guidelines are derived from empirical data and accelerating
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.
Post by john larkin
Communist thugs are the genocidal bandits. They have a captive market
and no competition.
Compared to the large-scale kleptocracies that replaced them? . . .

RL
john larkin
2024-06-08 14:40:50 UTC
Permalink
Post by legg
Post by john larkin
Post by legg
Post by Don Y
Post by legg
Post by Don Y
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).
The guidelines are derived from empirical data and accelerating
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?
Post by legg
Post by john larkin
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.
legg
2024-06-09 05:36:43 UTC
Permalink
Post by john larkin
Post by legg
Post by john larkin
Post by legg
Post by Don Y
Post by legg
Post by Don Y
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).
The guidelines are derived from empirical data and accelerating
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?
Post by legg
Post by john larkin
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.
In the US, the govt ensures that wall street is not inconvenienced.
Assets are stripped to pay dividends, labor juggled for a similar
benefit. Industry in north america is just not delivering.
Post by john larkin
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.
You're forgetting BYD, Brilliance, Chery, Changfeng, Geely, Great Wall
or any of the european-name-brand subsidiaries in India.

I've only ever paid for one car - had to pay for the telephone pole it
was totalled against, as well (it was that long ago).

Anyways - a bit of a non-sequitur , neh?

RL
Jasen Betts
2024-06-12 10:22:59 UTC
Permalink
Post by john larkin
Post by legg
Post by Don Y
Post by legg
Post by Don Y
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).
The guidelines are derived from empirical data and accelerating
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.
Or maybe you are the United Fruit Company.
Post by john larkin
Communist thugs are the genocidal bandits. They have a captive market
and no competition.
Not the only ones.
--
Jasen.
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