Muthu,

I'm no expert, but that won't stop me from trying to keep the
conversation going :-) [in fact, Feynman said that makes me
particularly qualified to keep the conversation going!]

Every sensor has precision with respect to full scale, and usually has
trouble measuring well at the lower end of range.  If you think of an
accelerometer as a block(weight) on a spring - kind of like a fish
scale.  The scale used to weigh a guppy will not be the same scale
used to weigh a tuna. The guppy will not even register on the tuna
scale.  And if you put the tuna on the guppy scale, unless it has
great bottom out protection, the tuna is going to break it and the
guppy scale will not measure correctly during the process.

From a G perspective, the kart is a tuna and the shopping cart is a
guppy. When apple demoed the i-phone as a gaming device in March,
[minute 41 forward http://www.apple.com/quicktime/qtv/iphoneroadmap/ ]
it looked like shopping cart resolution was within reach to me because
the motions were not so exaggerated. I was thinking of the
accelerometer as an accelerometer rather than a tilt sensor so I may
have misunderstood current capability. Early micro-machined elements
were a bit more like tuna scales, but they have always been good about
putting in hard stops to protect the sensor. A while back there was a
link to UCLA folks using accelerometers to analyze the difference in
smoothness between a skilled and beginning rock climber (pre fall).
That should be close to enough resolution to measure a shopping
cart...

So what I have been trying to communicate for a while here is:

1. The cell phone market is large enough to support micro-machined
market specific products - even if that includes multiple cascaded
sensors in a single device [it could be several different spring mass
scales or just different circuits looking at the same element].

2. Accelerometers can bridge GPS or tower based location data at a
much lower energy cost per data point delivered than anything except
maybe a card compass.  And this function should be ubiquitous as the
robustness of function in tough environments is better and handset
costs to implement this should be lower. Cost to society is less so
more people stand to realize benefits.

3. There are compelling use models that make the return on deploying
good accelerometers in inexpensive phones positive for society.

http://www.deutsche-telekom-laboratories.de/~esslgeor/georg_papers/ICMC07.pdf

http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1600617

http://www.dotdust.com/unconventional-use-of-your-mobile-phone-accelerometer-319.htm

http://www.allaboutsymbian.com/features/item/Accelerometers_Tilt_Sensors_on_Symbian_S60_3rd_Edition_smartphones.php

I had an older cousin get killed on a motorcycle and I have a finite
budget, so I gravitate toward non-motor sports... like mountain
biking... This guy is pretty good at it.  Wipes out at the end and
still finishes 3rd. I don't see that happening in motor sports:

http://www.freecaster.com/live/1000006_1005144

The menu on the lower right corner gets a walk though that is pretty
impressive. A good accelerometer can help capture details to improve
technique.

On Jul 8, 11:08 pm, "Muthu Ramadoss" <[EMAIL PROTECTED]> wrote:
> What's the noise? If the accelerometer cannot detect a device moving at a
> walking pace, then what's the real use for it? I'm not an expert, so asking
> the experts here :)
>
>
>
> On Wed, Jul 9, 2008 at 9:00 AM, JP <[EMAIL PROTECTED]> wrote:
>
> > On Jul 8, 4:20 pm, "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote:
> > > This one needs a little clarification.
> > > Kart racers have been using accelerometer based data acquisition
> > > systems with trackside beacons for accurate lap times for a while
> > > now.
> > Have you driven a kart? These things GO. This means accelerometers
> > have plenty to work with. A person pushing a shopping cart around a
> > shop is probably not even raising sensor input levels over noise.
>
> --
> take care,
> Muthu Ramadoss.
>
> http://cookingcapsules.com- nourish your droid.http://mobeegal.in- find stuff 
> closer.
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