A robotic surgical system is configured to determine whether a surgical instrument has been properly mounted to an arm of the surgical system. As the surgical instrument is moved into engagement with the arm, a magnet on the arm exerts an attractive force on a plate on the surgical instrument. As the instrument engages to the arm, load cell measurements and inertial measurement unit (IMU) information from one or more sensors on the arm are monitored to determine the mass of the instrument as well as the acceleration of the instrument as it mates with the instrument engagement interface. The system compares the load cell measurements and IMU information with what those parameters are expected to be when a surgical device assembly or instrument of that type is mounted. If the load cell measurements and IMU information deviates from what is expected, the system provides a notification to the user and prevents use of the manipulator arm until the surgical device assembly or instrument is properly positioned.