Need help for accelerometer use

[Manu68350]

Hello, all world. (sory for my english i'm french)

 

i use the mpu6050 for read the gyro and accelerometer.

 

i make actualy a submarine, the gyro are ok i read good the value,

 

For the accelerometer i not understood, what is the output value on real and world, because if i read the fifo directly i can look

i have g, ex: 8192 is 1g and the accelerometer tell me the good value.

if i read the real or the world the value is most not like the same data. if you can help me for understood this, your welcome.

 

 

and finaly my real problem is i not will g , i will km/h (speed)

 

i  have read a post forum about velocity meabe i not understood this.

 

if you can help me

 

Thanks a lot

 

Emmanuel

 

[rgsteele]

Hi Emmanuel,

 

In the output from REALACCEL and WORLDACCE, the acceleration due to gravity is subtracted from the result. In other words, if the accelerometer is stationary, the output for each axis will be zero. You can read an explanation of the difference between REALACCEL and WORLDACCEL here:

 

http://www.i2cdevlib.com/forums/topic/45-realaccel-vs-worldaccel-for-dummies/

 

As for velocity, well, I'm afraid you're out of luck. An accelerometer cannot measure velocity, only a change in velocity. If you know your initial velocity, you can integrate acceleration over time to approximate your velocity, but the accumulated error will quickly make your measurement inaccurate.