How to calibrate accelerometer?

Have you tested your accelerometer by CSD Tools? If not, try it. To enter CST Tools type ##310## in Phone app. Then choose Individual tests and Gyro & Accelerometer.

@atlochowski I did that and it's within acceptable bounds for that test but I would still like to calibrate it if it's somehow possible. Y-axis's acceptable bounds were -3 to 3 and that's more than I would like accept.

For everyone's information, the code for accessing CSD Tool is *#*#310#*#* not ##310##

Actual calibration of an accelerometer requires very expensive equipment, but I assume you wish to check the reading in static situation. Just placing the phone on table when using the CSD tool is not necessarily very accurate. If you wish to be more certain, you can use a simple bubble level to determine the plane perpendicular to the direction of gravity more precisely.

Unfortunately, I have no precise information on the Aquafish accelerometer, but it is normal that a MEMS accelerometer may have some transverse sensitivity, which may be couple of percent. In addition there is always some noise in the signal. Any acceleration measurements normally have an error boundary which is something like ± 3...5 % at least. As a result, trying to calibrate this kind of sensors very precisely is quite pointless in most of the cases.

@kkarioja Well I guess I don't want to actually calibrate the accelerometer but to correct the values digitally in the way Vatupassi app let's you calibrate its values to 0°. Right now in order to get y-axis to 0 the top of the phone needs to be lifted to a very noticable angle and I'd like to have that a bit more approximately fixed. I was just wondering if there's any possibility for an easy fix like that.