Accelerometers

[Eric]

Thanks for the kind works Ty,
Agh! I keep forgetting that such a magic device exists! Those little things are seriously slick

[Adrenalynn]

Look at it this way too:

An accelerometer gives you an acceleration vector ON an axis: X/Y/Z - Left/Right/Up/Down/In/Out - it doesn't give you any kind of positional data.

A gyroscope gives you rotation vector ABOUT an axis: Pitch/Yaw/Roll - it doesn't give you any kind of positional data

With both of the above, once you stop moving you are back at zero as far as they are concerned.

A compass gives you rotation ABOUT a single flat plane - it does give you absolute positional signal. Alas, it's not terribly accurate. (+/- a few degrees, typically)

You can also build a more accurate absolute compass using magnets and carefully positioned fixed hall effect sensors. They measure amount of magnetic field, similar to a compass, only in this case you'd be reading your magnets and ignoring the earth's magnetic field as "noise"

[Shozbot]

an accelerometer is: 4 strain gages mounted on a pair of hinges. the hinge holds a mass, like a very small door



strain gages are resistors that change resistance in proportion to changes in their length. NOT like pots, which have three connections. one single resistor that stretches or compresses. kind of a bungee resistor.

they are arranged in a Wheatstone bridge formation. I don't have the GAS to explain that on a sunday morning

the behavior of an accelerometer may be compared to the behavior of water in a bottle in a car. if the car is moving at a steady rate, or sitting still, the water is level. if the car accelerates or brakes, the surface of the water tilts. an accelerometer measures that tilt in one axis.