With Bitty Data Logger you can capture and chart accelerometer, magnetometer and temperature data from your micro:bit over Bluetooth. You can also export captured data for analysis in a spreadsheet or other application.
After capturing data, you can upload it to the internet and then download the data to a desktop computer for analysis in, for example, a spreadsheet. Perfect for school projects!
The associated micro:bit coding tutorial will teach you how to send sensor data from your micro:bit to Bitty Data Logger running on a smartphone or tablet over Bluetooth.
Accelermeters measure *acceleration* and express this as three values which we refer to as X, Y and Z. These values are "vectors" meaning they express both a magnitude (amount) and direction. In the case of the BBC micro:bit, with the micro:bit held flat with its LED display facing upwards and the edge connector facing toward you, the X value measures the amount of acceleration to the left and right of you. Y measures the acceleration in the direction away from you or back towards you whilst Z measures acceleration up or down. So X and Y describe acceleration in the two horizontal planes whereas Z measures acceleration in the vertical plane. Perhaps a picture would help :-)
The micro:bit uses values which are in multiples of one "milli-g" i.e. one thousandth of the acceleration due to gravity. Bitty Data Logger scales the values up to be relative to g itself.
Magnetometer data is available over Bluetooth from the micro:bit in two forms.
In the first form, simply entitled "magnetometer data" in the Bitty Data Logger application, magnetic forces are expressed as a collection of X, Y and Z vector values very much like the data we can obtain from the micro:bit accelerometer. The vector values measure the strength of magnetic force in the following three directions:
The strength of the force in a given direction and therefore the value of X, Y or Z is expressed in Teslas.
It's also possible to obtain data which provides a 'bearing' measured in degrees from magnetic north.
When you first power up your micro:bit after installing a hex file which supports magnetometer data over Bluetooth, you will be prompted to "draw a circle" by a message which scrolls across the display. Hold your micro:bit so that the display is oriented in the vertical plane and then slowly rotate it through 360 degrees. You should see a single LED pixel lit and it should move to the bottom of the display with respect to gravity. This strange process involves collecting both data about magnetic fields in the local environment and motion and results in your micro:bit being properly calibrated for use in that environment.
The magnetometer may generate strange looking data if used in an environment other than that in which the calibration procedure was performed. Motion may also affect magnetometer data. For best results, always reinstall the hex file and recalibrate in any environment in which you want to capture magnetometer data.