A fiber Bragg grating direct current sensor with temperature compensation based on electromagnetic force

A novel fiber Bragg grating direct current sensor with intrinsic temperature compensation is presented in this article. The operating principle of the sensor is based on the deflection of a cantilever beam due to the electromagnetic force between a static-iron and a moving-iron attached to the free end of the cantilever which is enclosed within a solenoid through which the current under test is passed. The deflection of the cantilever beam is measured by differential strain sensing using two fiber Bragg gratings mounted on either side of the beam, thus achieving temperature compensation. The sensor operation is theoretically described, and experimental measurements confirm the operation of the fiber Bragg grating direct current sensor up to 500 A. A 382-pm Bragg wavelength shift difference is detected when the current is 500 A. The test results are analyzed and discussed in the time domain and frequency domain. The resistance to electromagnetic interference immunity of the fiber Bragg grating sensor is improved compared with the strain gauge sensor.