as shown in fig4 incidentally line ll represents the output voltage of the photo diode 201 at the lower magnitude range of the input load and line lh represents the output voltage of the photo diode 201 at the higher magnitude range of the input load the amplifying unit 206 of the load sensor 2 includes a lower load amplifier 206 l and a higher load amplifier 206 h as shown in fig5 the lower load amplifier 206 l amplifies the input load signal at a higher gain than the higher load amplifier 206 h as shown in fig6 and 7 the amplifying unit 206 amplifies the input load in the lower magnitude range from zero to x by the lower load amplifier 206 l and the input load in the magnitude range higher than x by the higher load amplifier 206 h the amplified voltage of each of the amplifiers 206 l 206 h is separately converted into digital data by the communication i f 208 and sent to the airbag ecu 3 via the communication line s 1 the airbag ecu 3 includes an object examining unit and a airbag driving unit which are common in this technical field the object examining unit examines an object by comparing the magnitude of the input load with a threshold voltage if the object is presumed to be a pedestrian as a result of the examination while the touch sensor 4 provides a turn on signal the driving unit drives an airbag system to inflate the pedestrian protection airbag which is mounted in a front portion of the vehicle 9 thus the magnitude of load that is detected by the load sensor can be accurately converted into digital data without using additional hardware such as a logarithmic.