| 摘要 |
PROBLEM TO BE SOLVED: To recognize whether the communication was carried out with the ID tags of all objects which are stacked each other by calculating the inductance of a transmitting antenna and estimating the number of stacked objects from the calculated inductance in an ID tag communication mode. SOLUTION: When the tuning of frequency is over, an MPU 28 acquires the on/off information for every switch of a resonance capacitor circuit 39 from an on/off control circuit 42c and calculates the electrostatic capacity of the circuit 39 from the on/off information. Then the inductance of a transmitting antenna 32 is calculated from the information of the electrostatic capacity, and the number of object dishes which are stacked each other is estimated according to the said inductance and a data table stored in a ROM. Thus, no exclusive device is needed for estimating the number of staked objects and it is possible to recognize whether the communication was carried out to the ID tags of all objects (dishes) stacked each other. |
