Memsic Accelerometer Measuring Inclination
I have seen trying, without success, to measure inclination using Parallax's dual axis Memsic accelerometer per the following application paper and equation given therein:
http://www.memsic.com/data/pdfs/an-00mx-012.pdf
Which gives the resulting equation:
angle of inclination = arccos ( 0.707 x [noparse][[/noparse]Ax+Ay] / g)
The problem is that the result in terms of [noparse][[/noparse]xmG + ymG] gives·practically no·output. I wonder if the equation is in error or, more likely, I am not applying it correctly. The only puzzlement I note in the application paper is that in figure 1 the y axis is noted to be conforming to the lefthand rule; rather than the called for righthand rule. Even with this in mind, as Red Skelton would say, "Things just don't look right to me."
Please note: My application is for use in a moving vehicle, for which I need to eliminate vehicle acceleration. And, I need some magnitude of resolution in order to measure low inclinations. I can, of course, take care of nonlinear output and data smoothing.
Any math/Pbasic coding help is greatly appreciated,
David
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- Stephen
In Smart Sensors and Applications (available for free download from that link), Chapter 3 covers tilt with the Memsic Dual-Axis Accelerometer. This chapter covers the basics of obtaining tilt measurements, as well as scaling and angle conversion. You can also take a look at Chapter 6 Activity #5 which demonstrates datalogging acceleration forces.
I hope this helps, happy developing!
Jessica
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Jessica Uelmen
Education Department
Parallax, Inc.
I did not include any coding as I wanted some new thinking on the physics/math/Pbasic coding based on the application paper I referenced. I could have mentioned that, after many coding trials, I simply added the line:
tilt = xmG + ymG
to Parallax's demo program "MEMSIC2125-Dual.BS2" in the subroutine "Read_G_Force:". [noparse][[/noparse]Of course after defining 'tilt' as a 'VAR Word', and the debug command to display it.
I made up an experimental tilt rig, including a woodworker's digital angle meter to calibrate any 'tilt' output. The sensor was mounted in the vertical plane with the x axis at counterclockwise 45 degrees to the horizontal. Essentially there wasn't any change in·output when the rig was tilted·.?
I had reviewed the 'Smart Sensors & Applications' lessons but those programs, I believe, assumed that the sensor was to be used in a 'nonmoving' application in which any parasitic horizontal acceleration was zero.
Again, thanks for your interest. I will keep exploring.
The following was taken from another forum entry :-) :
"If it Stinks it is Chemistry
If it is Mushy its Biology
If it doesn't work its Physics"
cheers, David