Method of delivering a receptacle to an instrument

A method of delivering a receptacle to an instrument, comprising:

• positioning a carriage at a first location of the instrument, wherein the carriage comprises a rotatable puck and is configured to move from the first location to a second location of the instrument, and wherein the puck is configured to seat a receptacle therein;
• rotating the puck in the carriage about a vertical axis to position the puck in a desired rotational position;
• determining whether a receptacle is seated in the puck using a first sensor;
• if it is determined that a receptacle is not seated in the puck, calibrating a sensing system, the sensing system being configured to determine whether a receptacle is seated in the puck;
• after calibrating the sensing system, seating a receptacle in the puck;
• after seating the receptacle in the puck, using the sensing system to determine whether the receptacle is properly seated in the puck;
• and
• after determining that the receptacle is properly seated in the puck, moving the carriage from the first location to the second location.