I'm wondering about using an ultrasonic sensor, like maxbotix ones and I would need to make the sensor moving inside a plastic tube and take measure throught the plastic tube.
With some calculations and what I remember from my physics lessons, a sound wave can go through something if the wave length is longer than the obstacle thickness.
So this sensor emits 40khz soundwave, so if i'm not wrong a wave length of 8,2mm.
So a plastic tube with 1 or 2mm thickness could theorically let the soundwave pass.
But my question was : Does anyone ever tried this? Do I have to put something in the tube to avoir sound reflections? and these kind of sensors are enough powerful to be able to detect something outside the tube even after passing a 1 or 2mm plastic wall?
Thanks for your answers !