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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 ..."
Exsqueeze me?
I've written a wifi signal strength meter for an embedded product. During my research, I found it was pretty much standard to base the bumber of bars on the signal to noise ratio, not the raw signal strength.
This article gives me a hunch why my no-name laptop battery dies so quickly even when Ubuntu still thinks it has 10% charge and several minutes left. Didn't happen with the manufacturer's battery...
Ubuntu usually does an excellent job analysing how good your battery really is (not sure if it's the kernel ACPI or HAL or GNOME that's actually doing it). But when the battery lies so blatantly, it seems even Ubuntu can't keep my laptop from sudden death without a proper warning or shutdown.
Both my Blackberry and my Sony Ericsson sometimes decide not to connect a call when I have close to full signal. Judging from TFA this could then be because of high noise ratio.
At the same time, I have always wondered why my phones do not give me any indication why the calls were not connected at the time. They both just return to the main screen after a long period of connection attempts.
Dan doesn't seem to know much about batteries. Check out batter power discharge curves and such...
http://www.mpoweruk.com/performance.htm Remaining power is estimated based on the charge of the battery. If you notice on those graphs, when you get out to the end of the stored charge, it drops off very quickly, which is why the gauge goes from half to empty quickly.
It really does not matter what these meters say as long as they are consistent. From long experience, my grey-ware then interprets the bars to give me a realistic expectation of battery life or signal strength. Move along now please. Nothing of interest here.
The article was indeed interesting, and believable. But it has a bad case of [Citation-Needed].
Cites are not required for independently verifiable claims.
This is the difference between faith and science. If you give someone information that they can independently verify, and they base their belief on the results of their independent results, that's science (even if they are wrong, it's still application of the scientific method). If you ask someone to believe something based on the idea that a person who says it is trustworthy, that's faith (although not necessarily religious faith). Insistence on credible "cites" to bolster physically verifiable claims or observable reality is not functionally different from a belief in biblical inerrancy. Believing something "because [insert authority figure here] wrote it in a science book" is just swapping one shibboleth for another.
Well, actually it's a fancy way of saying that some humans decided to lie to you, because it was cheaper.
Suppose I were the great shaman Watta Sucka, and you came to me with a cold. You want it treated, and maybe some way to know how long it'll last. I have no clue how to tell you either. So I chant some incantations, smoke the holy hemp, and then tell you, "Oh, yes, the great spirits said that to be rid of your demons, you must journey on foot to the sacred lake behind the power company's dam, along the highway to the east, and wash yourself with the holy waters. And the closer to the lake you are, the better you will feel, as its great magic repels the demons of your illness. And for only $499 you can also buy the sacred ancestral GPS device, showing the progress of your illness in km to the lake. But, remember, you must travel on foot."
Basically I'd bet that a cold goes away in a week, walking to the lake takes about a week, and you'll probably start feeling better along the way. And even gave you a sort of a meter from sick to healthy, in the form of that GPS device.
Except it's bogus. It's a lie. I don't really know what's wrong with you and really how long it will take, and the GPS device doesn't either. Maybe it'll go away faster, maybe it's bird flu and you'll be dead by tomorrow, or maybe it's a pneumonia and you've earned yourself a lot of hurt and complications by trecking through the wilderness for a week instead of taking antibiotics and resting. But at any rate, it's a lie. The "meter" I gave you, doesn't measure what I claim. It measures distance, which may or may not correlate with how sick you still are, but it still just measures distance. It's a different variable.
One way to put it metaphorically is to say that that GPS device lies to you. But in practice, it was me, the great shaman Watta Sucka that really lied to you.
A lot of tech devices and meters and gizmos are really the same kind of lie, and whether its makers even realize it or not, they decided to lie to you. Really measuring X (whether that's battery life, or whatever) is often more complicated than they can bother to do, or costs more and thus would cut into their margins. So they decide to lie you instead, by putting a bogus meter there. It's the same kind of lie as my sacred GPS device.
A polar bear is a cartesian bear after a coordinate transform.
Car manufacturers so the same thing with the gas gauge. the top half is more than the bottom half. If the gauge on my car is sitting at half, I'm down to 24 Litres out of a 60 Litre tank. Also, there's a gallon or two left when the needle is at E.
Cadillac invented this in 1984 when they rolled out the electronic gauges which were linear. Customers complained about bad mileage despite the car being thriftier than it's predecessor. Some research showed that they were going by *how*often* they were filling up, not by *how*much*. So they made the gauge logarithmic and allowed another unaccounted for gallon at the end for safety.
It is dangerous to be right when the government is wrong.
They REALLY should bring that back, Hell, all manufacturers should put that kind of thing in their cars. I can't think of a better way to make going for high mileage widely "cool". Like trying for the high score on an arcade game.
"Hey, guess what? I got 48MPG on my way to work!"
"Oh yeah? Well I got 52MPG! Beat that!"
Just simply harnessing people's competitive drive (not to mention the desire to save money) could do more than all the hybrids in the world, though that would likely lead to people buying hybrids in a quest for ever higher mileage.
upon the advice of my lawyer, i have no sig at this time
There are a lot of factors involved that cause fuel tank gauges to not read linearly. For one, there is a "float" in the tank attached to a pivot arm that moves an arm across a rheostat to change resistance depending on tank level. Since the arm swings in an arc, the resistance change is not linear. Second, the tank is oddly shaped which throws off the reading. Third, there is usually a "reserve" capacity built in where the gauge may read empty, but there is still fuel in the tank below the level of the float. Fourth, there is usually a sump at the bottom of the tank whose purpose is to hold fuel while the vehicle turns around corners and such to avoid starving the engine of fuel during maneuvers. Fifth, during heavy maneuvers, fuel will slosh around the tank and cause the float to move up and down as it rides the waves, distorting the reading.
As you can see, it's complicated. Modern vehicles do a bit of signal processing to smooth out the reading (especially in cases like example #5 above, fuel sloshing around the tank) but it's not perfect. It's close enough though, and that's what counts.
I have AT&T and I think they got more bars in more places by using this simple formula. I now NEED 3 bars to reliably make a call. I used to be able to have some hope at 1 or 2, but not in the last year or so. I realize the point of this article is that bars don't mean anything anyway, but I feel they have been adjusted a lot recently.
1) Cell phones.
Cell phones use a so called RSSI value for the number of the bars. RSSI is a Relative Signal Strength Indication, which is a best guess of the device how well the data transmission will go. Most use SNR directly, some use a product of signal strength and bit error rate (BER).
The reason why it doesn't always match reality is that it's really a best guess by the phone, and reality is much more complicated than just that.
2) Laptop batteries.
Laptop batteries are using charge counters. Those are resistors with very small resistance ( 0.1 Ohm) tied to a precise voltmeter in a controller chip. By integration the controller knows rather well how much charge (how many electrons) have passed through it. With Li-Ion and Li-Pol batteries in use today, however, the situation got harder because the voltage of the battery varies a lot during discharge. Nowadays, modern batteries count energy, that is the product of charge and voltage as it moves in an out, giving a very precise output of remaining energy.
The reason some batteries die very quickly once they stop showing full is because as Li-Ion batteries age, their internal resistance increases. More energy is lost within the battery during the discharge process and the amount of energy lost (and voltage decrease) is directly proportional to the current taken from the battery. At the same time, modern devices have switching regulators which take more current when voltage decreases to provide the same flow of energy to the device. Combined, this means that once the battery voltage of an aged battery starts dropping, it drops very fast.
For cell phones, this is even harder, since they don't have charge counters - the batteries have to be cheap. There the remaining energy is guessed purely based on voltage. And old Li-Ion batteries will have almost full voltage when under light load, and fail when the load is applied, causing a phone to switch off.
just like car manufacturers are telling you that driving an SUV is good for your safety while they make them with cheap truck chassis that are less maneuverable and do not reduce the impact of a collision nearly as much as a car chassis.
Based on some of the replies in this thread, the manufacturers propaganda is working well. Suckers seem to be lining up to defend their death trap SUVs.
But your post has been modded funny, no doubt as an attempt by someone who has a bad case of buyers-remorse that they can't admit to, to attempt to undermine your insight by getting your post labelled funny.
I bet the crack-addled moderator likes the laughter track on "comedy" like Friends because it tells him when he should be laughing. So he projects this logic onto others, and cleverly comes up with modding you funny so the other SUV owners will think you were joking rather than being serious.
No doubt I'll get a smack for this... better leave the karma bonus on so they have to waste more mod points...
Car analogies break down.