Pulsed Eddy Current

Pulsed eddy current designs may include balanced and unbalanced coil designs. In this more complicated electronic system, a pulsed inductive field is generated in a transmitter coil. A set of or a single receiver coil then monitors the field. A significant feature in the design is that the receiver is only active when the transmitter is inactive. An electric pulse energizes the transmitter at regularly spaced intervals. As the transmitter coil?s field collapses, it creates a momentarily strong electromagnetic field. This field induces energy into any metal particle passing through the detector. As the energized particle discharges the energy, the receiver coils sense the eddy currents within the metal. The receiver electronics are set to accept these signals after the transmitter has already shut off and only the eddy current signal from the metal is present.

The timing of this receiver "gate" is selected to assure optimum detector efficiency. Thus "product effect" is automatically reduced without the artificial detuning circuits in balanced coil systems. The balanced coil, pulsed eddy current decay system used by PJ TECH is the most advanced in the industry. PJ TECH detectors were originally developed for the mining industry where conductive and magnetic ores required a detector with excellent discrimination capabilities.

In addition to the ability to operate in difficult product applications, the antenna arrangement is another great advantage. The antennas do not "surround" the belt and can be installed without cutting the belt or dismantling the conveyor. Similarly, the replacement of components does not require cutting or dismantling of the belt conveyor.


Metal Detection > Introduction / Technology & History