# Ultrassonic thickness gauge

Hi everyone, I would like to build an ultrassonic thickness gauge using an arduino and one or more chinese ultrassonic sensors (costs a few bucks each). The obvious question is precision. It would be used on sheets of rubber, foam and eva. I need a precision of at least 0.1 mm. My idea would be to position the sensor at a certain fixed height facing a flat surface underneath it, trying as much as possible to make it perfectly parallel. Lets say the distance of the sensor and the flat surface would be 500mm. I would put the rubber sheet of say 4.1mm of thickness on the flat surface and now the distance measured would be 495.9mm. How feasible is that? Thanks in advance!

``````long microsecondsToCentimeters(long microseconds) {
// The speed of sound is 340 m/s or 29 microseconds per centimeter.
// The ping travels out and back, so to find the distance of the
// object we take half of the distance travelled.
return microseconds / 29 / 2;
}
``````

5.8us per millimetre

0.58us per 0.1 millimetre

Do you think that a 62.5ns per instruction MicroController can handle this?

And if you had googled something like, oh, say, arduino hc-sr04 accuracy, you would have found that these things have nowhere near the accuracy or precision you apparently require.

Typical ultrasonic thickness gauges use a transducer that is in contact with the part to be measured.