Unrelated - they are doing an ultrasound to get an image (just like looking at a baby in the womb), this is ultrasonic thickness testing.
Enquired about a bulk buy, unfortunately customs & GST on an order over $1000 negate the savings. Might get a few in anyway.
I could have stacked five of them on top of each other to see what happens Alas not mine. Slowly finding new homes for them though.