An instrument carriage provides control of a surgical instrument coupled to the instrument carriage. The instrument carriage includes a control surface that is coupled to the surgical instrument to provide the control. A detection pin having a first proximal end that extends from the control surface is coupled to the instrument carriage. A magnet is fixed to a distal end of the detection pin. A carriage controller provides an indication that the surgical instrument is coupled to the instrument carriage when movement of the detection pin causes an output signal from a Hall effect sensor to exceed a threshold value that is stored in the carriage controller as part of a calibration procedure during the assembly of the instrument carriage. Surgical instrument removal may be indicated when detection pin movement causes the output signal to be less than an instrument removal threshold value of less than the instrument threshold value.