Accelerometer: different values on different devices?

Question

I am needing to implement a shake recognizer, and I am using the accelerometer on the device to that. However, when I check the values I get from the sensor, it appears that they vary wildly from device to device. For instance, I get a value range of 0-8 as force (after some calculations) on one device, and on the other 0 - 4.

So it looks like they have very different ranges.

Is there anything I can do to make these ranges equal. Or are there some variables that I can use to somehow calculate what a fairly hard shake would be?

Answer 1

The sensor should be calibrated.

Apparently it isn't. If the gain in the different directions (that is x, y, z) is not significantly different then it is enough to look for sudden changes in the length^2 of the accelerometer vector: x^2+y^2+z^2.

If the gains are also significantly different then you have no choice but to write an app for accelerometer calibration...

By the way, you are not the first one to report gross inaccuracies, see for example Android: the range of z-value in the accelerometer sensor are different on different devices.

Answer 2

The physical placement of the chip on the pcb and the securing of the pcb within the device and the construction of the device could all lead to different damping effects in responce to your shaking input force.

You don't say how your processing the sensor data there may well be effects related to sampleing and filtering performed at the driver level.

You clearly need to be flexible in your code with the range of values you expect and test on a good range of devices.

Answer 3

According to specification accelerometer should return Measures the acceleration force in m/s2. So it should be calibrated. One thing you could check however is the Sensor class's getMaximumRange() and getResolution()