a tension mechanism for a robotically - controlled medical device measures the tension applied to an actuation tendon to provide feedback to a robotic controller . in one embodiment , the device comprises an elongated instrument , an elongated member , and a base . the elongated member is coupled to the distal end of the elongated instrument , configured to actuate the distal end of the elongated instrument in response to tension in the elongated member . the base is located at the proximal end of the elongated instrument , and comprises a first redirect surface that redirects the elongated member . the first redirect surface is coupled to a lever element that is configured to exert a reactive force on a sensor in response to tension in the elongated member .