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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 ..."
The article was indeed interesting, and believable. But it has a bad case of [Citation-Needed].
Belief? Hope? Preference?The Existential Vortex
Who cares? When it's full, my laptop or cellphone works great. When it's empty, the thing stops working. When there's only a few bars left, I either plug it in / move to a different location. IMO, it perfectly performs its intended duty. Anything beyond that is geek pedantry and nitpicking.
An old-timer with old-timey ideas.
And I bet you're going to tell us next that DRM isn't for our own good and is just a way for conglomerates to steal more of our money with little effort done on their part. Hah!
skillful integration of two /. themes
"I already knew that"
"DRM is bad"
The engineers dilemma, at least for battery levels:
- how the real value taking into account all variances including current usage and thus constantly move up and down the value
- average out the results to something close, but not exact, since this is what satisfies most people
Jumpstart the tartan drive.
Is it just my luck or are all cars like that? You go 200km on the first 25% of the gauge, but can barely get to 550km before it's empty?
Signal strength and battery time remaining can get pretty complicated, the more you look into it. There are a ton of different measurements, historical information, performance expectations, etc. that are constantly changing based on how the device is being used, who is using it, etc. At some point, you need to condense all of that information into some pretty little bars that a *normal* user (i.e. someone who has never heard of Slashdot) can comprehend. Is there going to be some precision lost? Of course. Is the graphical representation going to convey all the data gathered and interpreted by the device? Of course not. But the idea is to make it as useful as possible.
Just because I can hook a shark from a boat, I do no offer to wrestle it in the water.
You statement implies that you think it is more useful for the battery meter to display the charge level of the battery rather than the approximate amount of run time left.
For 99.99999999% of the people on Earth (that's everyone other than you), I'm pretty sure that a linear run time indicator is wildly more useful than an actual charge indicator.
Nerd rage is the funniest rage.
There isn't standard regarding what reported dBm value should be associated with 1-5 bars. It is purely up to the discretion of the programmer. I have heard RSSI referred to as Relative Signal Strength Indication as well, because the value is at the mercy of internal A/D tolerances. I have seen several copies of the same radios in a lab, (Faraday Cage) report drastically different RSSI values (AKA Bars). Nearby RF sources can influence the signal levels as well.
So that part of the article is true. I dare say anyone who actually knows anything about RF won't claim, bars guarantee connectivity. To say that it is lying to you because you don't understand how it works, makes the submitter look silly. Definition of "Lie" from Wikipedia: "A lie (also called prevarication) is a type of deception in the form of an untruthful statement with the intention to deceive"
We aren't trying to deceive you, we give you the indication because it is better than nothing, and most of the time it is good enough.
[Showing signal to noise ratio] is then overruled by the marketing department because brand 'B' only uses the signal strength, so that makes your product look bad when compared side-by-side, since theirs has more signal bars.
Then show the signal in solid black bars and the noise in staticky bars. Suggest that the marketing department include something to this effect in the ad copy: "Sure you get a lot of bars, but are they good bars?"
Taking the article to heart, maybe the reason they have more bars in more places is because they start at 3 bars for no signal and go all the way up to 4 bars for full signal.
Nerd rage is the funniest rage.
It's simply Anthropomorphism. I talk to my car when it runs bad. I don't expect it to hear me or comprehend, but I do anyway. I talk to the computer, too.
When I talk to machines, for some reason it's always cursing, as in "GOD DAMNED PIECE OF SHIT..."
mcgrew's razor: Never attribute to stupidity that which can be explained by greedy self-interest
Not in the least because many common wifi chipsets don't make raw signal strength available to the rest of the system. Cellular modules do, but if you ask a phone maker how the number of bars corresponds to the error rate and signal strength, they won't tell you. Although a bit of experimentation reveals that as long as the error rate is low and the signal is above the noise floor, you get full bars. That's probably marketing.
The battery conspiracy thing is a bit silly. Rechargable battery chemistry follows an S-curve. There's a very short period at the beginning with the battery over the nominal voltage, a long and almost linear middle section, and a short period at the end where the voltage drops quickly. So a naive voltage measurement gives exactly as described in the article -- almost full most of the time with a quick drop at the end. A less naive measurement is very tricky because the voltage in the linear section depends not only on state of charge, but current draw, recent current draw, temperature, the age of the battery being used, etc. The best way to do it accurately is to track a particular battery through its charge cycle and monitor current in and current out. Smart batteries like those in laptops do. I don't think cell phone batteries are smart batteries.
You mean that something with as many variables as strength and quality of a wireless connection can't be reduced to a value of "bars" between one and five without loss of information? Say it isn't so.
Slow news day, apparently.
Or you could try to not get into an accident. The best way to do that is to drive a small, agile car and watch where you're going (I can tell you it really works wonders! Even just watching where you're going and minding the objects around you makes a huge difference!). But why go through all that trouble? It's better to get the biggest cudgel of a vehicle that's practical and let physics sort 'em out!*
*hint: your safety is not determined solely by the G-forces you experience in an accident.
"When information is power, privacy is freedom" - Jah-Wren Ryel
Or that the panels for your Trailblazer are cheaper than for the Cavalier. Repair costs have as much to do with insurance costs as the likelihood of an accident.
simon
I live in the snowbelt.
I've seen a lot of 4-wheel drive SUVs/trucks in the ditches, because they displace overconfidence (like you just did). Meanwhile I've driven a midsize or compact car, and have never had an accident in the snow. The key? "Don't drive faster than 30 miles an hour ya dope!"*
As for F=ma, there's also "energy absorbing crush zones" to consider. A crash-friendly chassis is more important than F=ma. i.e. 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). What matters is how well the vehicle ABSORBS the energy, not its weight. Also worthy of note: SUVs are more dangerous than cars. Why? SUVs rollover and smash the occupants.
* (By dope, I'm referring to those numerous persons I see driving 65 on the interstate during snowstorms... I always wonder how they think they're going to stop while driving on slush.)
The government is not your daddy. Its purpose is not to raid middle-class neighbors' wallets and give it to you.