A star communication network including a hub node and links couple to the hub node for carrying data along routes in W channels. In a disk device that has a disk medium, a head, an actuator, a control circuit, there is a conversion mechanism that sets a data area in the writing range of the disk that corresponds to the range of motion of the actuator, and converts a logical address to a physical address in the data area. In addition, for example, the capacitors are not charged prior to the clamp capacitor, whereby it is possible to prevent the inrush current from flowing from the capacitors to the clamp capacitor when they are connected in parallel with each other. The ECU receives impedance signals from a plurality of passive electrodes among the measurement electrodes other than the active electrodes.