Using The Footswitch/Tuner FT01 : - note 1 - note 2 - note 3 - note 4 - note 5   Note 3:   If the note is sharp, the wheel rotates clockwise.   If the note is flat, the wheel rotates anti-clockwise.   The speed of rotation indicates how far out-of tune the note is.   When the note is in-tune, rotation stops or is very slow.   In terms of note frequency, if the rotation is once per second then the error is 1Hz.