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184370_en-US
184370_en-US
Hey All,
My values with the MMA7455L seem a little strange to me. The MMA7455L is in 2g measurement mode, and the device is mounted top facing up.
Having said that my X, Y, Z are as follows:
X = 3F
Y = 3A
Z = 10
I am expecting Z to be closer to 3F as per the data sheet (http://www.freescale.com/files/sensors/doc/data_sheet/MMA7455L.pdf)
Any idea why this might occur?
Best Regards,
Mike
Hi Mike,
The numbers you show just look like gravity to me: two axes at close to the same value, and the third axis about 1g different. Although it the Z axis looks to be reading more than 1g from X and Y, I don't think it is out-of-bounds for an uncalibrated reading.
You could simply turn the board over and see if the reading reverses.
Depending on how your board is mounted the axis which contains g will change. If you are using the eval board and it is flat on a table then you can expect 1g on the z-axis. The accelerometer will have an offset on each axis which does need to be calibrated out. Each device will have a slightly different offset on each axis without the correction. The app notes for this device explain this. See AN3468.
Peter
I don't understand your response. With gravity pulling the accelerometer towards the center of the earth, the data sheet says the expected value is $3F. Not 0x00.
Gravity?