What components would be needed to build an ultrasonic thickness gauge to measure paint the thickness of paint coatings?

I need an ultrasonic thickness gauge, they work by sending a pulse through the material being measured (paint in this case). When the pulse strikes a denser material it returns to the sensor, the delay from the time of the pulse being sent to being received gives the depth. I anyone knows the components that would be needed, or ideally, a set of schematics could you be so kind as to help me out. Thank you.

The hardest part is the transducer - you need a piece of barium titanate crystal. Why do you need to use ultrasonics ? What's the substrate ? Steve
alkem (author)  steveastrouk8 years ago
I very well may not need to use ultrasonics, that's just what I was finding while shopping for one. The substrate is steel, approximately 1/4 in" thick and the spec's call for between 6-8 mill's of paint coverage.
You have it easy then - the surface is magnetic ! There are classic methods that measure how hard it is to pull a magnet off the surface, and there are eddy current methods, where the loss from a coil is proportional to how well the coil is coupled to the surface. The closer the contact, the bigger the loss. Can you measure the WET film, as its applied, or have you got to measure the finished dry film ? My father spent a chunk of his career designing instruments to measure paint films - he had a bunch of patents in them from years back, and I picked up a lot of the tricks from him.
alkem (author)  steveastrouk8 years ago
I could probably measure the wet film, I honestly don't believe it matters as long as the thickness is right when it dry's.