Depending on inclination, either a bulls eye level with roll & pitch gauges OR horizontal and vertical bubble levels with angle gauge are shown. Calibration feature to correct for accelerometer misalignment & different axis sensitivities.
For best results touch CAL and calibrate first. The Spirit Level is only as good as your accelerometer. For indication only. Don't damage your tablet or phone, use a real spirit level when appropriate.
Horizontal and Vertical Levels with Angle Gauge.
Touching the pause icon will hold the current reading until pause is pressed again.
Touching the zero button will shift the angle gauge to the current pointer position so that relative angles can be measured. Touching the reset button (appears once zero is pressed) will restore the angle gauge back to its original position.
Bull's Eye Level and Roll and Pitch Gauges.
Touch CAL to enter the calibration Screen.
There are 2 required steps for calibration, and three further optional steps.
If you have a known level surface then steps 1 and 3 are usually sufficient.
Steps 2 and 4 are used to get measurements with the device rotated 180 degrees such that the average can be used to determine the true level.
Step 5 is used for correcting different sensitivities in each accelerometer axis. This step is really only for lower quality accelerometers and usually best skipped if you have a newer device.
If you wish to clear all the calibration constants, click on Clear CAL. Otherwise, position the device as shown in the images and touch the CAL buttons, wait until a green tick appears before moving to the next stage. Support your device as necessary so that it doesn't fall over. Any calibration will be stored and used next time you run the app.
After calibration you will find the bull's eye level and horizontal levels are the most accurate. However if you turn your device 90 degrees or upside down, the accuracy of the level may decrease due to the accelerometer quality.