[SOLVED] how to calculate scale of adxl345 Accelerometer

[uday mehta]

I am new to use Accelerometer. I read datasheet of adxl345. but I didn't get what is its scale range.
I mean if I will use 16G then what what will be the maximum output. and how to calculate it?
(if the sensitivity is 35 lsb/g at 10-bit resolution).

 

[srizbf]

If the 10bit resolution is selected , then the maximum o/p is obvious.
maybe , you may refine your question , as it is not clear what is reqd?

 

[uday mehta]

If the 10bit resolution is selected , then the maximum o/p is obvious.
maybe , you may refine your question , as it is not clear what is reqd?

\

I am just testing a program and I got these values

256, -384, 1116
732, -494, -654
-2582, 838, 302
2794, -664, -3150

I didn't understand these values.
in datasheet of adxl345 I read that at 16g it has 13 bit resolution. so what would be the maximum output?

also Accelerometer measures acceleration forces
then why in still position(no movement) I am getting some output like
-38, 14, -280
38, 18, -276
?

 

[srizbf]

the three values are 'g' values in x, y and z direction.

the first set,
256, -384, 1116

indicates : x=256 , y=-364 and z=1116

adxl345 measures g values in + and - directions of the
three axis x , y and z.

unless you program it for 13 bit reading , adxl will give only 10 bits.

\
....also Accelerometer measures acceleration forces
then why in still position(no movement) I am getting some output like
-38, 14, -280
38, 18, -276
?

in still position , it will read the g values in the three axis , depending upon its orientation (wrt to earth?).


just , try to change the position of the pcb of adxl , you can see that the values changes.


keep it perfectly horizontal , then it will give reading for z axis only.

 

[uday mehta]

thyanks srizbf.
if I select 13 bit resolution then will the max output +/- 4096.

 

[srizbf]

13bit resolution , gives that. yes.