Simultaneous Time-domain and Frequency-domain Metal Detector
With an estimated 100 million mines and countless millions of acres of land contaminated with unexploded ordnance (UXO) worldwide there is a need for a sensor system and methods that can detect and identify large and small metal objects buried in the soil. In addition, during armed conflict, there is a need for mine detection and neutralization in real-time or near real time. A commonly used sensor for mine and UXO detection is the electromagnetic induction (EMI) metal detector. Conventional EMI detectors using either frequency-domain (FD) or time-domain (TD) eddy current methods can detect small targets at shallow depths and large metal targets at deeper depths. However other metal objects commonly found in the environment form a major problem in identifying mines and create many false alarms. These false alarms cost time and money when trying to clear an area of the real mines. Metal targets need to not only be identified but also classified in real-time.
The Johns Hopkins Applied Physics Laboratory has developed and is in the process of patenting a metal detector capable of operating in both a time-domain and frequency-domain mode that includes a transmitter and receiver component. The transmitter component includes a transmitter coil that can generate both an AC and pulsed DC current or voltage source for frequency- and time-domain operation respectively. The AC signal is impressed on the pulsed DC signal such that while the transmitter coil is switched off (pulsed), time–domain sensing is occurring. The receiver component is in a balanced configuration with respect to the transmitter to ensure that both time-and frequency-domain modes can operate with the magnetic field receiver.
Patent Status: U.S. patent(s) 7,078,906 issued.CONTACT: