Contactless sensor driven by single power supply

摘要

A sensor contactlessly driven by a single power supply is disclosed. A current flows in a resistor RL through the secondary winding of a coil in the direction corresponding to the direction of magnetic fluxes generated in the coil in accordance with discharge or charge mode of a main battery. The input terminal of a voltage follower is connected to the voltage-dividing point of a series circuit including resistors R1 and R2 and a reference voltage control circuit. The reference voltage control circuit changes the input voltage of the voltage follower in accordance with the direction of the current flowing in the resistor RL. It follows therefore that the measurement range is switched in accordance with discharge or charge mode of the main battery, with the result that the overall measurement range can be widened in spite of the fact that only a single power supply +Vcc is used.