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Your Computer and Cell Phone Are Lying To You
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 ..."
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.)
No, that's because the base station that you're getting your signal from has no bandwidth left. You could be standing next to the antenna, and have 'full' signal, but if 'all circuits are busy' you're SOL regardless of the signal strength.
#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.
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...
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
I used to work for Motorola, and I can attest that the standard 3 bar battery gauge showed:
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.
Hint: Rally is done in small, agile cars, not in SUV's
After living in Alaska for nearly 20 years, I have found that if the road surface is so slick that braking is essentially nil, I can almost always stop the car and avoid an accident by gently nudging the curb with my tires. Unless you've already screwed up so badly that you are spinning out of control, there is almost always enough traction to change your direction of travel by a few degrees, and by rubbing your front tires against the curb, you can get enough traction to stop just about every time. I've only had to do this a couple of times when road conditions at an intersection were much worse than the conditions on the rest of the road, but it has always worked.
MCSE? No, sir...I don't do Windows. Yes, I am an idealist. What's your point?