Beijing Information Science and Technology University 1 article published in JoVE Engineering A Random-displacement Measurement by Combining a Magnetic Scale and Two Fiber Bragg Gratings Lianqing Zhu1,2, Lidan Lu3,4, Wei Zhuang2,5, Zhoumo Zeng3,4, Mingli Dong1,2 1School of Instrument Science and Opto-electronics Engineering, Beijing Information Science and Technology University, 2Beijing Engineering Research Center of Optoelectronic Information and Instruments, Beijing Key Laboratory for Optoelectronics Measurement Technology, 3School of Precision Instrument & Opto-electronics Engineering, Tianjin University of Science and Technology, 4School of Precision Instrument and Opto-electronics Engineering, State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, 5School of Instrument and Opto-electronics Engineering, Hefei University of Technology A protocol to create a full-range linear displacement sensor, combining two packaged fiber Bragg grating detectors with a magnetic scale, is presented.