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 ..."

Comments

Pshaw

[MistaE]

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!

Re:Pshaw

[cushdan]

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"

Re:Pshaw

[Godji]

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, 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. Hah!

Re:Pshaw

[GameboyRMH]

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.

Re:Pshaw

[Shinobi]

Hint: Rally is done in small, agile cars, not in SUV's

Re:Pshaw

[electrictroy]

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.)

Re:Pshaw

[element-o.p.]

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.

[Citation-Needed]

[FredFredrickson]

The article was indeed interesting, and believable. But it has a bad case of [Citation-Needed].

Re:[Citation-Needed]

[zappepcs]

There is no citation needed. I can personally attest to the fact that unless you pay tens of thousands for the equipment it's metering capabilities are ONLY an indicator, more or less like your gas gauge, and not some sensitive sensing system. period. ever.

Most of the work done on electronics in the world is done without exacting measuring equipment. Yes, there will be those that argue, but *MOST* work is done with less than optimal equipment. Think that mechanic working on your car is using micrometers to do everything, or $2500 torque wrenches? For most of the world, good enough is ... well, good enough. Battery monitoring systems can only count down from full charge based on use and time. At best it is a simple calculation that cannot do much to account for aging of the battery or temperature compensation.

No citation needed. That is simply how life is, and why this is a huge 'duh' article, even if joe bloggs doesn't realize it. It's the reason that your vehicle gauges are not calibrated. This applies to just about everything we use.

Re:[Citation-Needed]

[fabs64]

I know it's de rigeur, but that was quite a lot of writing for someone who didn't RTFA.

Dan is claiming that (at least in cell phones) there is a deliberately misleading fudge factor.

Re:[Citation-Needed]

[amram9999]

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.

Re:[Citation-Needed]

[dotancohen]

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.

Re:[Citation-Needed]

[electrictroy]

Every car I've ever owned has worked the same way. The bar will remain on "F" until 60% is reached, and then it gradually starts dropping. When the gauge claims I have "1/4" I really only have 15% of my fuel tank left.

I've heard stories of car companies trying to make more accurate gauges, but the customers complained that the car was "half empty" after "only" 150 miles. They prefered the old gauges that still showed almost-full, even though those gauges were lying.

So I suspect the real conspiracy is just "the ignorance of the average citizen" that led to deceptive gasoline and battery meters.

   

pedantry

[caffeinemessiah]

Neither display is actually telling you what you think it's telling you.

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.

Re:pedantry

[PlatyPaul]

Hey! My battery bar is full! That's must mean I have at least a few hours le

Re:pedantry

[urcreepyneighbor]

Anything beyond that is geek pedantry and nitpicking.

That is Slashdot.

Re:pedantry

[Anonymous Coward]

These types of posts are getting on my nerves.
If you battery went you would not of made the post at all...I'm not stupid.

Re:pedantry

[travdaddy]

Maybe he was dictating it.

Re:pedantry

[jez9999]

Actually, (s)he could have made the post if their battery went half way through, and here's why. The char

Re:pedantry

[dotancohen]

what's the English word for using a meme incorrectly?

/.

My laptop tells me how much noise there is.

[sudog]

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.)

Wifi meters

[lisaparratt]

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.

Re:Wifi meters

[lisaparratt]

Not only can I write software, but since I can multitask, I can do your mom at the same time.

Re:Wifi meters

[tlhIngan]

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.

... which 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.

In the case of cellphones, it's the carrier that determines how the bars map to signal strength (or quality, if it's possible to estimate). Some carriers demand that you show 5 bars down to a really pathetic signal strength value (I've seen close to -100dbi - just as a quick comparison, most wifi chipsets lose all connectivity between -80 to -90dbi, and the best tend to disconnect around -96dbi). The headroom between that and when the baseband loses the signal completely isn't that much.

Which is why I laugh when I hear "More bars in more places". It's easy to get a "stronger" signal if you mandate that a phone must show more bars all the time.

Now, this was for a non-GSM phone, so it was mandatory to get carrier qualified. But GSM carriers are equally bad, except they don't have as much control since you can bring in any compatible phone onto the network. The only thing the carrier can claim is their phones get a "better" signal (see? more bars than your phone!).

I wonder if Apple had to jump through these hoops with the iPhone or just said to the carriers to screw it - they're designing the software their way and that includes battery and signal strength meters that make sense. Given what I see of cellphones, there's often a special baseband/firmware build for each carrier to cope with the differences... but the iPhone software seems to be either unified, or just a single build around the world. (Carriers oblige because the customers want the phone).

Re:Wifi meters

[russotto]

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.

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.

Laptop Battery Dying Too Soon

[Renegade Lisp]

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.

Batteries

[fitten]

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.

Re:Batteries

[maxume]

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.

Re:Batteries

[imsabbel]

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...

Grey-ware needs input.

[Therefore I am]

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.

GASP

[oodaloop]

Are you trying to tell me that the constantly changing field of electro-magnetic radiation pouring through my laptop does not always match up precisely to the five bars in the display? Frankly, I find that hard to believe.

Comment removed

[account_deleted]

Comment removed based on user account deletion

Re:Ummm, doesn't "lying" imply free will?

[hansraj]

I would have given you the answer, but I suppose you would rather that I speak axiomatic set theory or such.

Re:No connection on a full signal

[Steve J 83]

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.

Easier for sales

[glindsey]

Cingular loves to tout "More bars in more places".

"Higher signal-to-noise ratio across a broader range of the United States" just isn't quite as catchy a slogan.

Ugh

[Se7enLC]

#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.

Oh thank God!

[oahazmatt]

Your Computer and Cell Phone Are Lying To You

Oh, thank God! I was worried I was the only one who could hear them!

Re:Ummm, doesn't "lying" imply free will?

[rodney dill]

anthropomorphism is a common human tendency... get over it.

now if I can just get my laptop to stop humping my leg....

As a developer

[timias1]

I have written code specifically around converting RSSI (Received Signal Strength Indication) into those signal bars, and a couple of things.

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.

Re:Ummm, doesn't "lying" imply free will?

[sm62704]

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..."

Re:gauges

[compro01]

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.