Separating Permanent and Induced Magnetic Signature: A Simple Approach
Magnetic signature detection provides sensitive detection of metal objects, especially in the natural environment. Our group is developing a tabletop setup for magnetic signatures of various small and model objects. A particular issue is the separation of permanent and induced magnetization. While the latter depends only on the composition and shape of the object, the former also depends on the magnetization history. With common deperming techniques, a significant permanent signature may still remain, which confuses measurements of the induced component. We investigate a basic technique of separating the two. Measurements were done by moving the object along an aluminum rail while the three field components are recorded by a detector attached near the center. This is done first with the rail parallel to the Earth magnetic field and then with anti-parallel orientation. The reversal changes the sign of the induced- but not the permanent magnetization so that the two can be separated. Our preliminary results on a small iron block show excellent reproducibility. A considerable permanent magnetization was indeed present, resulting in a complex asymmetric signature. After separation, a much more symmetric induced signature was obtained that can be studied in detail and compared with theoretical calculations.
 Wiegert, R. (2003, September). Magnetic anomaly guidance system for mine countermeasures using autonomous underwater vehicles. In OCEANS 2003. Proceedings (Vol. 4, pp. 2002-2010). IEEE.
 Brown, P., Whiteside, B. J., Beek, T. J., Fox, P., Horbury, T. S., Oddy, T. M., & Carr, C. M. (2014). Space magnetometer based on an anisotropic magnetoresistive hybrid sensor. Review of Scientific Instruments, 85(12), 125117.
 Zou, N., & Nehorai, A. (2000). Detection of ship wakes using an airborne magnetic transducer. Geoscience and Remote Sensing, IEEE Transactions on, 38(1), 532-539.
 Nguyen, T. S., Guichon, J. M., Chadebec, O., Labie, P., & Coulomb, J. L. (2011). Ships magnetic anomaly computation with integral equation and fast multipole method. IEEE Transactions on Magnetics, 47(5), 1414-1417.
 Wagemakers GPM and Somsen OJG. “A table top setup for experimental magnetic signature detection”. Proceedings of the International Naval Engineering Conference. Amsterdam. May 20-22, 2014.
 Liu, H., & Ma, Z. (2007, September). Optimization of warship degaussing decision based on poly-population particle swarm algorithm. In Evolutionary Computation, 2007. CEC 2007. IEEE Congress on (pp. 2719-2724). IEEE.
 Lenz, J and Edelstein. S. "Magnetic sensors and their applications." Sensors Journal, IEEE 6.3 (2006): 631-649.
 Pham, M. D., Low, K. S., Goh, S. T., & Chen, S. (2015). Gain-scheduled extended kalman filter for nanosatellite attitude determination system. Aerospace and Electronic Systems, IEEE Transactions on, 51(2), 1017-1028.
 Cheung, S., Coleri, S., Dundar, B., Ganesh, S., Tan, C. W., & Varaiya, P. (2005). Traffic measurement and vehicle classification with single magnetic sensor. Transportation research record: journal of the transportation research board, (1917), 173-181.
 Caruso, M. J., & Withanawasam, L. S. (1999, May). Vehicle detection and compass applications using AMR magnetic sensors. In Sensors Expo Proceedings (Vol. 477).
 Zou, Y., Wang, G., Wu, K., & Ni, L. M. (2014, October). SmartSensing: Sensing Through Walls with Your Smartphone!. In Mobile Ad Hoc and Sensor Systems (MASS), 2014 IEEE 11th International Conference on (pp. 55-63). IEEE.