Power calculating device.

摘要

A power calculating device including a control signal generating unit (6) connected to receive a first voltage corresponding to a voltage of a system under measurement for generating a control signal (a, b). The control signal determines a power calculating period and an imbalance compensation period based on the fist voltage. The device also includes an input voltage changeover unit (7) for changing over between the first voltage and a constant voltage under the control of the control signal (a, b) to generate a second voltage, which is the first voltage during the power calculating period and the constant voltage during the imbalance compensation period. The device further includes a Hall element member (3) for generating a third voltage corresponding to a product of the second voltage and a magnetic density generated by a magnetic field applied to the Hall element member (3). The device also includes an imbalance detecting unit (8) for generating an offset compensation signal based on the third voltage, and a variable resistor (10) connected to the Hall element member (3). The resistance value thereof is changed by the offset compensation signal, whereby an imbalance voltage of the Hall element member (3) is compensated. <IMAGE>