| 摘要 |
PURPOSE:To enable the detection of an obstacle existing at a close range down ahead of a bumper or the like without detecting the road surface even when the sensor is installed at a low point of the body of an automobile or the like. CONSTITUTION:This ultrasonic sensor has an ultrasonic transmitter/receiver 1, a transmission signal circuit 2 which outputs an ultrasonic pulse intermittently to the ultrasonic transmitter/receiver 1 at a specified frequency, a receiving amplification circuit 3a which amplifies a received signal received with the ultrasonic transmitter/receiver 1 between one and the subsequent transmission. It also has a received signal processing circuit 3 which compares the received signal amplified with the receiving amplification circuit 3a with a specified threshold to detect an object and a reporting means 4 which receives an output signal from the received signal processing circuit 3 to notify the presence of the object. The received signal processing circuit 3 is provided with a gain control signal circuit 3e which lowers a gain of the receiving amplification circuit 3a by a specified level according to the passage of time between one and the subsequent timings of transmission. |
