helenebene / ardu-imu

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Conversion of acceleration seems wrong (via Accel_Scale macro) #12

Open GoogleCodeExporter opened 8 years ago

GoogleCodeExporter commented 8 years ago
What steps will reproduce the problem?

Serial.print(Accel_Scale(Accel_Vector[2]));

What is the expected output? What do you see instead?
Using the conversion from ADC-values to accelerations by the defined scaling:

#define Accel_Scale(x) x*(GRAVITY/9.81)//Scaling the raw data of the accel to 
actual acceleration in meters for seconds square

produces unexpected values. 

-> expected is an acceleration in m/s2 in z-direction of about 9.81

To be correct, the conversion should be defined as:

#define Accel_Scale(x) x*(9.81/GRAVITY)//Scaling the raw data of the accel to 
actual acceleration in meters for seconds square

to produce the expected output!

What version of the product are you using? On what operating system?
I'm using 1.5, but its still in 1.8 

Original issue reported on code.google.com by some...@online.de on 8 Jan 2011 at 12:40

GoogleCodeExporter commented 8 years ago
I believe the code is right but the comment is wrong. Accel_Scale actually 
takes an acceleration in m/s^2 (e.g. the centripetal acceleration) and scales 
it to an ADC value that is subtracted off of the measured accel ADC value.

Original comment by reiteran...@gmail.com on 20 Apr 2011 at 8:10

GoogleCodeExporter commented 8 years ago
Oho, yes, that makes sense too...

Original comment by some...@online.de on 23 Apr 2011 at 9:33

GoogleCodeExporter commented 8 years ago
...after thinking about it...

-> Accel_Vector is float, because of the Over-Sampling mean values of the ADC 
(not because its in m/s²), I'm fine ;-)

Thanks a lot!
Sven

Original comment by some...@online.de on 25 Apr 2011 at 11:53