I bought a therapeutic ultrasound machine from eBay and wanted to know if it really produces the claimed power output (it does). It's supposed to provide up to 3.4 W/cm^2. The transducer is claimed to be 1 inch diameter although the face of the transducer is larger. To measure the power I followed the IEC61161 methods and some ideas outlined in the links below, making a single 45 degree reflector (easier than the cone) from aluminium and measuring the force with a small scale that can detect small changes in weight ( 0.01g ).
The pivot point is a piece of the blade from a light duty snap-off utility knife that slots into a 3d printed knuckle.
The balance part comprises the 45 degree plate and a wire with a sliding screw that is used to roughly set the weight on the scale to a reasonable value.
To do the ultrasonic output power measurement
I have no reference to say how accurate my setup was, how important degassing the water is, etc. but when set to 3W/cm^2 I measured 2.7W/cm^2 which was close enough for me to be satisfied that the device was working.
You don't need to 3D print anything but for me it was the simpler route to get a working measurement.
A few references
The author marked this model as their own original creation.