Hi. I am in a middle of a project which requires proximity/distance sensor. My first attempt was to use ultrasonic HC-SR04 as I have used one before. However in the middle of the build I have noticed that HC-SR04 is not sensing clothed objects properly(ie hand with a glove on). But my other project seems to be sensing things like that with no problem at all(I can hear it`s sound pulses). Sensors did came from different sellers and have slightly different markings on them.

One that works https://www.dropbox.com/s/d8gvse0pf3erumz/2016-04-04%2021.24.04.jpg?dl=0

One that fails https://www.dropbox.com/s/e49sx776nb00kv2/2016-04-04%2021.27.03.jpg?dl=0

Does anyone run into a similar problem? And what are other options for proximity sensing? Thanks for any suggestions ;]

Soft, fluffy or rough surfaces do not reflect sound very well, too much absorption or dispersion. The same for visible or IR light.

I'd think that a camera will allow to detect movement of objects, if that helps.

I can hear it`s sound pulses

You can hear an ultrasonic pulse ? Isn't that a bit of a non sequitur ?

Hi, Have you swapped sensor units to make sure it is not the hardware/power supply of the other that makes it good.

If you can hear something, it probably means the transmitter is being powered so hard it is producing sub harmonics.

Tom... :)