I have a question about ultrasonic sensors.
By connecting the car parking sensor to the scope I always get the same wave. But by changing the distance from the sensor, the parking system respond as expected (according to my distance from the sensors)
From my understanding i should see the sent wave (which i do) and after some time the echo signal (which i don't). if sound travels at a speed of 340 m/s (2.9ms for each meter) and i am 0.5 meters from the sensor i expected to see the echo signal attenuated after about 2.9ms which i don't although the car parking sensor does show i am 0.5 meters from the sensors. i thought perhaps the signal is highly attenuated, going as low as 50mV but all i see is noise. could it be that the frequency is inside the noise? even the noise does not appear to change.