Problem with 6dof accelerometers (ADXL320 version)

Archive SparkFun Site Questions/Comments
1

Hey

I’ve been messing with my 6dof with the adxrs150’s and the adxl320’s. There seems to be a persistent problem with all three adxl320’s. Their sensitivity seems to be much higher when tilting to one side than the other. For example, on the roll axis, tilt (left down, right up) causes a very sensitive adc out change while a tilt (right down left up) scrolls through 3-4 values (center and 2-3 more values: 510-517-531-548) until the maximum value. It’s almost as if the accelerometers were not designed to measure “negative” tilts/deaccelerations.

Has anyone experienced this behaviour? I read the data sheet from www.analog-devices.com and did not found any reference to this behaviour.

My first thought was that i might have chosen a wrong sensitivity/resolution for my application (i chose the 320’s which do +/- 5g’s) but if that were the case, the problem should persist nomatter which direction i tilted the platform to, right?

I can post a movie (screen + imu board) with this effect if anyone is interested.

2

This is very odd indeed. The accelerometers don’t care which way you tilt them, they should be equal.

I don’t have a good answer. Have you noticed anything else?

-Nathan

3

Not really. I thought it could be some problem with either the mcu or the mux but it happens on all axis and the sensitive values come from the same pins as the not-so-sensitive ones.

I’ll mess some more with it this week and weekend and post back more feedback plus a link to a movie with the reading captures and board tilting.

Filipe

4

if u need temp hosting for the movie, email me with the move and i will put it on a server.