Your device *must* be equipped with a gyroscope for Gyroscope Explorer to work. I cannot stress this enough. Gyroscope Explorer does not give your device a gyroscope, it must be equipped with a gyroscope from the manufacturer.
Gyroscopes are relatively new on Android devices and are usually only equipped on device manufacturers "flagship" phones/tablets. So, unless you have recently purchased one of the more high-end devices available, the chances are that your device does *not* have a gyroscope. If you open Gyroscope Explorer and you get a message saying that the gyroscope does not exist on your device, your device is either not equipped with a gyroscope, the device has been rooted or the manufacturer never implemented the gyroscope in the Android API.
If you do have a gyroscope, be aware that the quality of the drift compensations on the gyroscope sensor vary considerably among devices. In the case that your device has a gyroscope that doesn't work well, there are multiple option to fuse the gyroscope with the acceleration and magnetic sensors. These option, which uses a fusion of the acceleration, magnetic and gyroscope sensors via complementary filter or Kalman filter to determine the rotation of the device, is far more reliable that the gyroscope sensor alone.
You can now log the output from the gyroscope and filters to an external .CSV file.
Gyroscopes measure the rotation of a device with a pair of vibrating arms that take advantage of what is known as the Coriolis effect, which is caused by the Earth's rotation. By measuring changes in the direction of the vibrating arms caused by a rotation and the Coriolis effect, an estimation of the rotation can be produced. The gyroscope is one of three sensors that are always hardware based (the other two are the magnetic and the acceleration sensors) on Android devices. In conjunction with the acceleration sensor, the gyroscope can be used to create other sensors like gravity, linear acceleration or rotation sensors.
If your device is equipped with Android 4.4 or higher, you *might* have the uncalibrated version of the gyroscope so you can see how drift affects the gyroscope sensor relative to the calibrated gyroscope.