| 摘要 |
<p>Various electrical coin testing arrangements are described which may be used in coin sorters or in coin validators for example. In each arrangement a transmit coil is pulsed with a rectangular voltage pulse and the eddy currents in an adjacent coin under test are monitored, either by monitoring the resulting current in the same coil or in a different coil. In one arrangement, Figure 7, particularly suitable for a coin validator, a single coil 3 acts as both a transmitter and receiver and is successively pulsed with voltage pulses of different lengths, and the decaying eddy currents are measured by measuring the coil voltage after delays which are longer for longer voltage pulses, in order to reduce the dynamic range requirements of the monitoring circuitry A, M. In a second arrangement, Figure 4, two transmit coils 3, 4 are used, the larger coil 3 being larger than each of the coins 6 to be tested, and the smaller coil 4 being smaller than each coin.</p> |
