RobotStudio event

Noise problems when connecting encoder to plc of the robot

Recently, i try to connect encoder to plc of robot(q01u) to try read speed of the conveyor.The problem is the noise from other terminal in plc is really difficult to handle as i dont have experience in this .So anyone has any suggestions or solutions to this.
the encoder im currently working with is HN3806-ab-600f.Thanks in advance