Open Loop-Type with open circuit characteristically displays output as output voltage in comparison to the current measured. The power voltage supplied to sensor is displayed as output voltage. The output is displayed in the same way as the measured current and as the proportional voltage through the operational amplifier located within the sensor. Therefore, this serves as an advantage for the user to conveniently administer connection to A/D converter of reception circuit or input terminal of operational circuit by using the common power source without the necessity of any special measures. The rated current is to be set in the ratios of 1/2 or 1/3 within the range of output linearity. This is to secure sufficient output range within the saturation range of supply power voltage and internal magnetic substance in measuring current with high peaks. In relations to setting of load in output terminal, it is to be set as 10ohm or more for open loop-type so that the output current is not higher than 10mA. Also, it is recommended to use twist pair or shield wires for input/ output wire in order to prevent and suppress noise in the signal line. Caution is required to use current sensor of open loop-type because heating of the magnetic substance may occur due to the influence of magnetic loss, etc. of internal magnetic substance in measuring current of high frequency.. When handling sensor in areas surrounded by ferromagnetic substances, it is required to set the optimal environment in terms of the position and direction of use..