A short ultrasonic pulse is transmitted at the time 0, reflected by an object. The senor
receives this signal and converts it to an electric signal. The next pulse can be transmitted
when the echo is faded away. This time period is called cycle period. The recommend
cycle period should be no less than 50ms.
If a 10μs width trigger pulse is sent to the signal pin, the Ultrasonic module will
output eight 40kHz ultrasonic signal and detect the echo back. The measured distance is
proportional to the echo pulse width and can be calculated by the formula above. If no
obstacle is detected, the output pin will give a 38ms high level signal.
1.0 Seeed Ultrasonic Sensor
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