Accelerometer

Dec 11, 2008 3 Replies
J

Hi,



I am planing to use an analog accelerometer ( ADXL330KCPZ) in a project. And i have following questions


  1. The accelerometer will place flat on the table. How can I get or calculate the angle information from the three outputs of the accelerometer? I will read the outputs via 12 bit analog to digital converter. So, there will be three numbers of 12 bit data.


  1. How can I calbriate the readings? For example, the accelerometer is no longer on the flat table but installed on the wall, the reference has changed.


Please advice!



Thanks John


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S

You have to integrate 3 signals twice, and end up with a highly unstable signal drifting all over the place. Also you have to add 2 gyros, and integrate those once. Airplanes use this, and those platforms cost ~ 100.000 dollars, to get the needed accuracy/stability.

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B

2) Assuming this accelerometer responds down to DC, you can calibrate simply by turning it in 90 degree steps: When its axis is vertical you have +1g, horzontal is 0g, inverted is -1g. Repeat for all 3 accelerometer axes.

Best regards,

Bob Masta DAQARTA v4.51 Data AcQuisition And Real-Time Analysis

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J

Expanding for question 1.,

1) The sensed acceleration varies from 0g to 1g according to the angle of the device's sensitive axis to the horizontal, from 0g when parallel to 1g when perpendicular. The angle with the horizontal will be the arcsin of the g value, or the arccos if referenced to a vertical line.
John
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