You need to learn how to count clicks and seconds. For a simple measurement, press briefly - turn on. Press a second time - it will start measuring without showing anything on the screen, press a third time - it will show the result. To measure, press briefly. For continuous measurement press for 1.5 seconds To change the reference point mode (beginning or end of the device), press for 3 seconds. Press for 5 seconds to turn off. The main thing is not to confuse :)