topic Accelerometer problem MMA7455L in Sensors

Accelerometer problem MMA7455L

vishu — Tue, 03 Feb 2026 22:18:54 GMT

Hi,

I am using the accelerometer MMA7455L which is connected to the micro controller (9s08Aw32) via the I2C bus. I am able to communicate to the accelerometer and read the X, Y and Z axis values from the accelerometer. But, even when the board is idle, the X, Y and Z axis values are changing everytime I read.

For Example: When the accelerometer is not moving, the X and Y axis values should be 0 and Z axis value should be 1. Even there are any deviations in these values, it can be calibrated to show the proper values. But I am not getting any constant values everytime I read the accelerometer. The values are varying in a range of 30 to 40 points which is not acceptable.

Does anybody has any idea as to why this might be happening?

regards

Vishu

Re: Accelerometer problem MMA7455L

mcarino — Wed, 15 Oct 2008 03:18:10 GMT

Use a moving-average (low-pass) filtering algorithm for the input data.

Re: Accelerometer problem MMA7455L

vishu — Wed, 15 Oct 2008 04:10:12 GMT

Hi,

Thanks for the suggestions.

But is the behaviour of the accelerometer is correct?

Is this how the accelerometer outputs will be?

regards

Vishu

Re: Accelerometer problem MMA7455L

mcarino — Wed, 15 Oct 2008 10:41:33 GMT

You weren't very specific as to what the measurements "are," but as long as you followed everything that's suggested in the datasheet, then yes. According to the datasheet, the 0g measurement can vary by as much as 40 ticks (I really shouldn't be doing this for you, vishu).

If you want less quantization error, make sure you use 2g measurement sensitivity. Also make sure you've decoupled all of the supply inputs.

Like I said, you can get a nice accurate measurement if you low-pass the measurements from the accel.

Message Edited by mcarino on 2008-10-15 04:43 AM