Toward an Automated Setup for Magnetic Induction Tomography

Magnetic induction tomography is a noncontact electromagnetic imaging technique that has potential applications in security, industry, and medicine. This paper describes an automated setup developed to image metallic objects. The instrument employs a pair of coils in the Helmholtz configuration for the driving field and a planar array of 400 sensor coils. The sample object is imaged via phase variation measurements between the driver and sensor coils´ potential difference, due to inductive coupling between the coils and sample object. The imaging system is automated via LabVIEW. A multiplexer with 400 channels automatically connects each sensor coil to a dual-phase lock-in amplifier, so that measurements of voltage phase-difference between the sensor and driver coils could be taken. These measurements were used to generate an image of the sample object. The planar geometry of the sensor coil array makes the system scalable to a full 3-D imaging system, by simply adding two more driver and sensor assemblies orthogonally to the existing one. However, this requires the ability to image objects at a finite distance from the array plane. An experiment was conducted to explore the imaging capability for various heights of sample-lift-off above the array. This proved that the system is scalable to a full 3-D imaging system.