Your Computer and Cell Phone Are Lying To You 479
Ant writes with a story from Dan's Data, which says that the battery meter and connection-strength displays in your portable electronics are lying to you, "and not just when they whisper to you in the night." Quoting: "Mobile phones, and most modern laptops, have signal strength and battery life displays. One or both of these displays has probably been the focus of all of your attention at one time or another. Neither display is actually telling you what you think it's telling you. The signal strength bars on a mobile phone or laptop do, at least, say something about how strong the local signal is. But they don't tell you the ratio between that signal and the inevitable, and often very considerable, noise that accompanies it ..."
My laptop tells me how much noise there is. (Score:5, Informative)
And I even have a little meter for it mixed in with my signal strength.
I find it pretty useful.. I'm pretty sure everyone's wireless chipset can tell them how much noise or at least how many mangled packets arrive. It's just the little dummy strength meter doesn't convey any of that. I liken most of those sorts of things to the CEL light in cars anyway. Good to know when something's not *perfect* but not so good for understanding why (nor whether it's just a gas tank cap seal broken, or a head gasket blown.)
Like my fuel tank (Score:2, Informative)
On another (more geeky) note, it's also like the progress bar of any install program. It take 2 minutes to get to 98% done, and another 5 minutes before the install is actually completed.
Progress bars, meters and measurement instruments are there only to give you an approximate indication of where you are compared to where you were. Some are more precise (ruler, multimeter) than others (battery life, signal strenght).
Re:Fuel gauges also lie (Score:3, Informative)
Comment removed (Score:3, Informative)
Re:No connection on a full signal (Score:4, Informative)
Ugh (Score:5, Informative)
#1, even with a voltmeter you can't reliably predict battery life. With an alkaline AA battery, you could watch the voltage drop from 1.5V down to 1.1 and know that it was now dead - but with newer rechargeable batteries, the voltage doesn't drop until it's completely dead, so you can't easily guess how long it will take. The only way to do it would be to have the device keep a history of how long it is able to work before the battery dies completely and statistically predict future performance. As if they are going to waste time doing that!
#2 Yes, noise should be considered, but an exact signal to noise ratio isn't going to predict bandwidth or call quality, either. I'm pretty sure that the "signal" they measure is actually signal-to-noise anyway. But even just signal strength is still useful, since you can assume that noise isn't changing that much.
Gas gauges? How many people see that their car stays "full" for a long time and then drops sharply? Or says that it is empty when there's still a few gallons left? Mine will tell me "0 miles to empty" and drive for another 50 miles without coming close to empty. Speedometers? They can be off by 5 or 10% right from the factory. Really every gauge is inaccurate by some amount.
My guess is that companies make the gauges vague on purpose, so that people DON'T try to get too much (false/misleading) information out of them. If your cell phone can make a phone call with "2 bars" of signal, that is all the information you should be taking away from that measure. And if your battery says full for 2 days and drops sharply on day 3, you know that when it starts to drop it's time to charge it. That's all the information you need. Does anybody really think that consumers will be happy with a voltage display? I don't even know what voltage my phone operates at, let alone what the low-end of operating voltage will be.
Re:Batteries (Score:5, Informative)
No, like the article, you dont get it:
They use this curves to make a voltage->charge conversion.
But take a look at them, and guess what will happen if there is only small calibration error/battery defect/heat influence, that shifts the voltage a few 10mV: Suddenly, you might already be on the curve sloping down while the device still thinks its in the middle of the platau.
Smart electronics try to learn from past discharge behaviours, but for many gadgets, its just not possible: The ipod you left in your car in the summer will behave diffrent for the next charging cycle than the one that was near freezing in the winter.
The cellphone that was just running for a week in standby will behave different after the next charge compared to the one that was drained dry in 3 hours by watching divx videos on it.
And dont even mention partial chargings, which add a hysteresis on top of this things.
Its a very difficult problem, and devices really try their best to solve it.
But there is a reason why the controller board of a bigger laptop battery (that has 1% accurate meassurements) is bigger than you whole cell phone...
Re:[Citation-Needed] (Score:5, Informative)
50% of the battery life at 3 bars
30% at 2 bars
15% at 1 bar
5% at 0 bars
And yes, this was customizable by the carrier to make it better or worse. Of course, this is hard to prove to the sceptics unless the software is open source.
There are numerous other technical reasons why the gauges might not be accurate, but this is a big factor.
Re:Ugh (Score:3, Informative)
That's a guiding principal for conveying quantitative information. There's accuracy, and there's precision. The accuracy of a measurement tells you how correct the measurement is relative to the actual value you're trying to measure. The precision tells you how specific the measurement is, or to put it another way, now narrow the range of actual values the measurement covers (since there is always a bit of uncertainty in a measurement.)
For example, I could tell you that the temperature is 95F outside. There is an implied precision of 1F (+/- 0.5F) in that measurement. I could also say that the temperature is in the 90s, which has an implied precision of 10F. (+/- 5F). That's precision. If the actual temperature is 65F, then despite the precision of my measurements, they're very inaccurate.
The guiding principle is that the precision with which you convey information should match the accuracy. If you have a digital thermometer that shows the temperature in tenths of a degree, it had better be accurate to within a tenth of a degree, otherwise it is misleading. On the other hand, if your thermometer is a color changing material that is blue when it's cold, green when it's moderate, and red when it's hot, you'd better label it 'cold moderate hot' rather than put a temperature scale with 1 degree precision on it.
Many developers (and other people) get this completely wrong, and report numbers with far too much precision.
Re:Remember retractable cell phone antennas? (Score:3, Informative)
It doesn't matter whether it was connected or not. It had an effect, thanks to the black magic which is RF. Moving pieces of metal (or even plastic, if they weren't metal) around in a cell phone can't help but have an effect. Granted, it may not have been the effect the users wanted, but it was an effect.
Re:Ugh (Score:4, Informative)
1) Li-Ion and Li-Po batteries have internal chips that can tell exactly how much charge is in a battery (you've never over-charged a Li-based battery). The curves are much more flat but under load it's not especially difficult to know the charge state quite accurately. Heck, IBM even will tell you the charge/discharge current to two decimal places with some of their utilities.
2) You're guessing. In addition, noise is often more dynamic than signal levels. SNR is a MUCH more accurate determination of quality of bandwidth.
Gas guages, yes they're inaccurate - likely because manufactureres assume people are stupid. I just watch the pump and see how much gas i put in, subtract from the full-tank size and it's not so hard to determine how accurate the guage is. Speedo's are allowed to be a certain % off of actual but you have to take into account that the diameter of the tires on a car change as they wear. So yes, consipracy theory this and that but a speedo is not going to be perfectly accurate by measuring the drive shaft rotation.
Did you even glance at TFA? You're simple repeating much of what was said. The rest - assuming people are incapable of reading a simple guage frightens me. I mean, if you have to coddle the general population because they're all THAT stupid we've got bigger issues than the last 3 minutes of talk time on your cell.
gauges (Score:2, Informative)
Along with that they had a somewhat nice MPG readout that you could see fluctuate widely, if you punched it from a complete stop, it dropped to something dismal like 6-7 MPG, on the highway, flat, cruising just the double nickle and back off a little it would briefly hit 44 MPG, then settle down again to like around 28 or so IIRC, been a long time now.. At least that is what I remember of them, that particular one was en el dorado, used to work on this medium rich guy's small fleet of vehicles for him so I drove all of them on occasion.
Reasons for inaccurate battery data (Score:3, Informative)
It is quite common for laptop batteries to overestimate the remaining time, it even gets worse the older the batteries are: As they expose a sudden and sharp voltage drop at the lower end of their capacity, it really is hard to determine, how much time really is left.
So even though the manufacturers tend to program too optimistic parameters into the drivers, they are bound to be inaccurate as time is passing and the batteries get old.
You can use tools like IBAM from http://ibam.sourceforge.net/ to profile your batteries more accurately and gain more trustworthy readings for your time left running on batteries.
Re:Ugh (Score:1, Informative)
but with newer rechargeable batteries, the voltage doesn't drop until it's completely dead, so you can't easily guess how long it will take.
It really is possible to gain some information from the voltage, but it is not as linear as with alkaline batteries: First the voltage declines very slowly during discharge, and then there is the sharp drop. So it is harder, but not impossible.
The only way to do it would be to have the device keep a history of how long it is able to work before the battery dies completely and statistically predict future performance. As if they are going to waste time doing that!
With "more intelligent" batteries they continuously measure and add the discharge and charge currents to estimate the remaining capacity.
Still this isn't too accurate either as the batteries are not 100% efficient and they do wear out over time.
But you can get your accurate statistics you were talking about using ibam [sf.net] on your smart phone or laptop.
Uhh... (Score:2, Informative)
What is the part from:
"Cites are not required for - independently verifiable - claims."
you do not understood? You really not a scientist
Is too easy to create many "citations" and put then on article to say "Hey, this is true because have citations!", I can say "my citation is from is the holy bible!" :)
But, a thing you can explain to others "how to test yourselves and conclude this is true" is a different matter and do not need a [insert your favorite VIP here] to say "is true", you only need to test yourself
Re:Pshaw (Score:5, Informative)
Hint: Rally is done in small, agile cars, not in SUV's
Re:Pshaw (Score:1, Informative)
http://en.wikipedia.org/wiki/Tire#Mud_and_Snow [wikipedia.org]
Re:Pshaw (Score:1, Informative)
The personal downside is that you're more likely to be in an accident if you are in an SUV
That's because the vast majority of people that drive them are arseholes.
Re:Pshaw (Score:5, Informative)
Re:Pshaw (Score:2, Informative)
Indeed. Much better to drive an Abrams tank down the road and get 4MPG @ $4+ /gal than say... a smaller more fuel efficient vehicle. God only knows what people like me do (I drive a 2007 Ford Focus.) Oh wait... I look around and pay attention to the people on the road. Like the guy who cut across 3 lanes of traffic traveling at ~75MPH in an SUV. Why? Simple...what am I going to do, NOT move out of his way?
I've noticed that a slight majority of people who drive SUV's drive them like tanks. I've been flipped off, laughed at and cut off more times than I can count by them. All because of F=ma and the low-brow neanderthalic thinking that a lot of people get by driving the biggest thing they can get their hands on.
Archangel_azazel
Re:Pshaw (Score:2, Informative)
Depends on where you live in the Midwest actually...
--Veteran of far to many pop vs. soda holy war discussions from college
Re:Pshaw (Score:1, Informative)
WRONG!
Hint: Rally is done in whatever works. Porsche won the 1986 Paris-Dakar rally in a modified 959, which was a fancy ass version of the 911 sports car (smallish, but not what the guy in 2nd expected to be following)
And just a few weeks ago, Porsche won 9 of the top 10 spots on the Transsyberia rally from Moscow to Mongolia with a bunch of Cayenne S *SUV's*. (The ones old "purist" Porsche fans love to hate) Toyota made it into 7th with one car. Subaru was completely missing from the top 10. oops.
http://www.motorsport.com/news/article.asp?ID=300056&FS= [motorsport.com]
since your confusion about rallies seems to have prevented you from doing a 20 second search of Google before spouting such silliness in public.
Re:Pshaw (Score:2, Informative)
A better equation is f=dp/dt. Not only is it more correct (consistent with relativity), but it is important to consider the change in momentum, not just the mass of the object when talking about vehicle collisions.
>A 5000 pound SUV that remains solid like a brick (but turns its occupants into scrambled eggs) is a lot more dangerous than a 2000 pound civic that crumples like a wad of paper (but protects its passengers from damage).
while it's true that the ability to absorb energy is important to vehicle safety, this statement is simply incorrect.
The statement is half correct when your talking about hitting a (mainly) unmoveable object (like a wall) (your explanation is wrong). Yes the force on the car will equal the cars weight times the instantaneous acceleration (of the car), but the force on the human will only be the humans weight times the instantaneous acceleration (of the human). And I'm pretty sure your weight does not change regardless of what car you drive. The reason for driving a car that crumples is that it speads out the total change in momentum (impulse) over a longer duration of time, when compared to a car that remains rigid (your total impulse depends on your mass, your initial velocity and your final velocity). As a result the maximum force on your body will more likely be lower due to lower dp per dt (Likely because we are talking about instantanous momentum change which will depend on how the cars are built. the average force will definitly be lower if the impluse is the same as the car that crumples will have a longer collision time).
Your statement is incorrect when your talking about a collision between two vehicles, in which case, the heavier car will win out almost every time (assuming same safety features, i.e. airbags and seatbelts, and weight of driver). The reason for this is because the driver of the heavier vehicle will always experience a lower total impulse. Example: head on collision between two cars (Weight including drivers: 5000kg going to the right and 2000kg going to the left) at 30m/s; drivers weight 100kg; inelastic collision.
Momentum Heavier car: 150000Ns -->
Momentum Lighter car: 60000Ns Final momentum: 90000Ns --> Final velocity: 12.86m/s -->
Total impulse of driver of heavier car: |100kg*(30m/s-12.86m/s)|=1714Ns
Total impulse of driver of lighter car: |100kg*(-30m/s-12.86m/s)|=4285Ns
Now the total time of collision will be the same for both drivers, hence the driver of the heavier car experience less force. (Note: the total impulse of driver and car is the same for both vehicles but not the total impulse just of the driver)
This scenario plays out in a similar way with different kind of vehicle to vehicle collisions as well (assuming inelastic collision).