As a part of ongoing research projects at University West in the area of robot welding applications, a study was looked-for in the field of feedback control of robot systems with external sensors. A literature survey was performed in this field. A virtual instrument was developed in a PC using the LabView software from National Instruments. The instrument receives a signal from a force sensor, converts the input data and sends out the computed signal on a configured serial port. This information is then received by the robot system to be used to control the robot trajectory. The system was tested and it showed that external closed loop control of robot movement was possible to do. Problems with high delay time in the ABB IRB2400 robot system limits the bandwidth or the speed of the closed loop system. This delay time is caused by the intrinsic offset function that is needed to change robot path during motion. This function requires a great computational cost. The conclusion is that ABB IRB2400 robots, with the S4 controller, are limited for applications with low bandwidth because of their motion computation program structure. It does not allow for external feedback applications that require higher robot movement speeds.