| 摘要 |
<p>A coin discriminator measures both the surface and average electrical conductivity of coins in order to distinguish genuine minted coins from fake coins such as cast coins which may be nominally of the same material as a minted coin. The conductivities are measured using a coil to induce eddy currents within the coin. The high frequency components of the eddy current are monitored to measure the surface conductivity. The low frequency components are measured to monitor the bulk conductivity. First and second signals are derived for each coin to provide a measurement set for that coin, the first signal being a measure of the conductivity of the surface skin of the coin, and the second signal being a measure of the conductivity of the body of the coin. The measurement set is then compared in some way with stored sets of reference signals obtained from minted coins in a calibration procedure.</p> |
