I was wondering why ACCELERATION data is not equal or close to zero. Do I need to calibrate by myself or maybe I totally misunderstand the ACCELERATION(then forgive my ignorance:)


Your tag is accelerating roughly at 9.81 m/s^2 (or 1000 mG) towards the center of the Earth :wink:
You can apply high-pass filter to data if you want to get rid of the gravity component in acceleration data.

As Otso wrote, the resulting vector should be 1000. Since this is the resulting vector, the values of x, y and z will depend on the orientation of your sensor. If by calibrating you mean to get a value of zero at rest, this could prove a bit tricky.

I am currently using a Ruuvi Tag to detect movements on my front door. It is working very well and I get a Pushbullet warning every time the door moves. Since I have a fairly fixed setup, I use a calibration process to “zero” x, y and z so as to easily detect movements registering more than 200 mG.

I can also log the data to

If you want you can try my soft (AutoBuddy) but if you do, let me know so I can update the config process to include logging :wink:

You would also need the version of the firmware I wrote. (Download here)

As the guys already pointed out, on earth you’ll see that kind of result, which will vary slightly based on your geological location and altitude.

The reason behind this is that the accelerometer measures proper acceleration which is the physical acceleration experienced by an object, for example due to gravity or change in velocity by waving the tag in your hands (which is coordinate acceleration).

Based on your message, I assume you want to measure coordinate acceleration, which can be difficult depending on your scenario, as @frawau pointed out.
Usually the easiest way to do this is to know the orientation of the tag so you can then subtract the gravitational acceleration from the measurements and you’ll end up with only the coordinate acceleration.
Most mobile phones do this by measuring the change in the magnetic field direction and using a gyroscope (among other things) to detect the true orientation of the device, however unfortunately the RuuviTags have no magnetometer or gyroscope so you need to get creative with this one.

1 Like