Feedback Devices

A closed loop system requires a feedback device (encoder, resolver or tachometer) to provide a signal (speed and position) back to the drive/servo controller ensuring that proper operation has occurred. The controller takes the data provided by the feedback device and compares it to the desired set value.  Any difference (error) would result in the controller sending a correction to the input of the process.  A closed-loop system cannot be any more accurate than the feedback device controlling it.