| 摘要 |
Apparatus for determining whether an object (5) is an aluminium can comprises an oscillator circuit (60) for generating a reference signal. A drive coil (10) responsive to the reference signal emits a magnetic drive signal towards the object (5) and a sense coil (20) generates a detector signal from the magnetic drive signal after it has passed through the object (5). A phase comparator (3) is connected to receive the reference signal and the detector signal for generating a bilevel comparison signal whose duty cycle indicates the degree of phase coherence between the signals and an analyser circuit (R8, C7, 40) responsive to the comparison signal indicates that the object is not an aluminium can if the duty cycle is greater than the determined values. |
