A method of delivering a receptacle to an instrument includes positioning a carriage at a first location of the instrument, rotating a 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 a receptacle is not seated in the puck, calibrating a sensing system 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 a second location of the instrument.