# Tri-axial Accelerometers

1. Dec 13, 2008

### Murs

Hi,

I am very new to accelerometers and I don't seem to be making any head way with them and I was wondering if someone could tell me what would be my first step in calculating acceleration on the X axis.

2. Dec 13, 2008

### brewnog

Well the tri-axial bit is irrelevant if you're only considering one axis. What type of accelerometer do you have, and what are you using to measure its output?

3. Dec 14, 2008

### Murs

Hi,
I am concerned with all the axis( X, Y, and Z ) but I figured if I was told how to find one. I would be able to figure out the others. I am using a ±1.5g Three Axis Low-g Micromachined Accelerometer. So far all I am seeing are the accelerometer ADC values

19.405 2318 2038 2037
19.605 2320 2044 2036
19.805 2323 2049 2035

In the Format: <timeSec> <accX> <accY> <accZ>

The problem is I don't know what to do with these values to find the acceleration in each of the axis.

4. Dec 14, 2008

### DyslexicHobo

I only worked with an acceleromter briefly 2 years ago as a freshman project, but shouldn't there be some sort of rating for the meter (I think the one I worked with happened to be .01v/g). Knowing the voltage output you can calculate acceleration.

I did only get a B for the course due to troubles with hooking it up to an 8-digit display, so I probably don't know what I'm talking about. :P

5. Dec 14, 2008

### Murs

Hi,

The voltage output for the
XOut @ 0g = 1.65V
YOut @ -1g = 0.85V
ZOut @ 0g = 1.6V

I would greatly appreciate it if you could tell me how the voltage output can help you calculate acceleration - Or anyone else that knows and can help me

Thanks!!

6. Dec 14, 2008

### DyslexicHobo

A spec sheet for your accelerometer may help. Do you have a model number?

7. Dec 14, 2008

### Murs

8. Dec 15, 2008

### timmay

You have a zero point and a sensitivity for each channel. Basically, using the values given in your data sheet (and comparing to what you've posted):

Acceleration (g) = (Output in mV - Zero point in mV) / (Sensitivity in mV/g)

So for example...

Acceleration (g) = (850 mV - 1650 mV) / 800 mV/g = -1g

Hope this helps.

9. Dec 15, 2008

### Murs

Thanks Man!!

Much appreciated