Patent ID: 8665301

Claim:
A method of operation of a tape drive ( 10 ), including obtaining the circumferences of a pair of spools ( 30 , 32 ) of tape, the pair of spools ( 30 , 32 ) including a supply spool ( 30 ) upon which tape ( 34 ) is initially wound, and a take-up spool ( 32 ) for receiving tape ( 34 ) unwound from the supply spool ( 30 ), each spool being mounted upon a respective rotatable spool support ( 12 , 14 ) which is mounted in a housing ( 11 ), such that tape ( 34 ) extends along a tape path between the spools ( 30 , 32 ), there being provided a sensor assembly ( 16 ), the method including rotating the take-up spool support ( 14 ) and the supply spool support ( 12 ) simultaneously, so as to feed tape ( 34 ) from the supply spool ( 30 ) into the tape path, and to wind tape ( 34 ) on to the take-up spool ( 32 ) from the tape path, determining a length of tape ( 34 ) fed into the tape path by the supply spool ( 30 ) during a measurement period using the sensor assembly ( 16 ), monitoring the angle through which each of the spool supports ( 12 , 14 ) has rotated during the measurement period, regulating the length of the tape ( 34 ) in the tape path, such that the length of the tape ( 34 ) in the tape path at the start of the measurement period and the length of the tape ( 34 ) in the tape path at the end of the measurement period are substantially the same, and using knowledge of the length of tape ( 34 ) fed into the tape path during the measurement period and the angle through which each of the spool supports ( 12 , 14 ) rotated during the measurement period to obtain the circumferences of the supply spool ( 30 ) and the take-up spool ( 32 ).