G-Tech meter

[Peter Ballam]

On Apr 30,  7:28am, dzorde wrote:

> How does it measure the distance (doppler effect ?), or does it calculate
> distance from your acceleration ?  If this is the case how does it go in
> hilly areas, bumpy roads, etc ?

>-- End of excerpt from dzorde

A few years ago I used to design airborne missile telemetry which uses amongst
other things accelerometers. I would speculate that the distance is calculated
from your acceleration. Effects like bumps and hills should have little effect
as the sensor is directional so only your cars forward direction is measured
plus/minus a tiny amount from the effects of gravity and bumps which will act
at 90 degrees to your measuring axis and so have the least effect. So unless
you are climbing up a wall the errors should be very small.

I would also speculate that the effects of wind/rh and your cars wind
resistance
would effect the values more, as would of course any wheel spin. So the close
readings may just be a coincidence, unless the device has lots of other
parameters etc to be entered so that most factors are taken into account.

To increase the accuracy you could always do a run in both directions to invert
the effect of any slope and the wind unless the wind is blustery rather than
constant.

			Bye,

-- 
Peter Ballam B(H)Eng            SGS Thomson Microelectronics,
CAD Development Engineer        1000 Aztec West, Almondsbury,
                                Bristol, England, BS12 4SQ.
Email peterb at bristol.st.com     Tel/Fax +44 1454 611380/617910.