Coaxial EMI Sensor for UXO Detection and Discrimination
Abstract
The environmental problem addressed with this technology concerns the task of detecting buried unexploded ordnance (UXO) in a cluttered site, with discrimination between them. A technology that can accomplish UXO detection with clutter discrimination in an efficient manner (high production rates, low cost of operation) would provide the Department of Defense (DoD) with a tool that could have great impact on the cost of UXO cleanup. The coaxial coil configuration electromagnetic induction (EMI) sensor is motivated by the potential advantages of the common mode rejection of electromagnetic noise from external sources. The balanced differential receiver (gradient) measurements reject voltages induced by noise fields that are uniform over distances on the scale of the receiver coil separation, including natural sources such as sferics (distant lightning induced), geomagnetic storms (sun spot induced), platform motion in the geomagnetic field, and man-made sources such as power line fields. The platform motion induced noise has been shown to be particularly problematic for the vehicular towed concentric-coil system (GEM-3) in the operational frequencies below 100 Hz. One penalty paid with the coaxial geometry is an increased height of the transmitter coil, reducing the excitation field strength over the target. There is a trade-off between increasing the coil separation to increase the difference signal and reducing the separation to reduce the transmitter-target distance, and the design must provide a good compromise for the anticipated target depth envelope. Also, small separations pose an engineering challenge at achieving adequate bucking (receiver coil balance). For this seed project, the objective was to verify these principles rather than demonstrate an operational sensor. The extension to a multireceiver array with single large transmitter loop constitutes the implementation of an efficient system for wide area coverage using a vehicle-towed platform.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 2008
- Accession Number
- ADA607132
Entities
People
- Bill Sanfilipo