| 摘要 |
PURPOSE:To accurately discriminate type of material and mass, etc., by initially setting a bridge circuit including at least one sensor coil to an unbalanced state in advance, and setting the circuit so that it is significantly changed in response to the variation of such as type of material to be detected. CONSTITUTION:For example, when a balancing ratio is set to 5.5, an unbalanced voltage of a bridge circuit 1 with a sensor coil 1 apparoached with a material to be tested such as iron, i.e., an output voltage of an operational amplifier 3 is as shown in the table. Thus, when an output is -0.75V through the adjustment of a lower limit value setting resistor R4, if the 1st operational amplifier 3 produces an output, silver coil, aluminum, brass and copper out of the materials to be tested can be discriminated from iron. If the operational amplifier 13 generates an output only when the output voltage of the operational amplifier 3A is <=-0.5V through the adjustment of an upper limit setting variable resistor R3, only the silver coin can be discriminated from others, brass and copper. Thus, the discrimination of type of material and mass can be performed. |
