Do you feel like many of the transducer measurements you are doing seem redundant like a 5 legged chair? For example, why would we use a d33 tester on crystals when we do impedance analysis? We get much of the same information from both.

Why measure transducer velocity with a vibrometer when system performance parameters and electrical measurements already give a good indication of how well a transducer is performing?

There are three reasons why you should have some redundancy in your measurement methods:

1. Some methods are more error prone than others. Multiple measurements using different principles give confidence that no single method is in error
2. Each measurement method is in fact a little different even though similar phenomenon are measured. Therefore, each gives us a nuanced way of looking at the data
3. One measurement method may be superior than another for reasons you cannot 100% predict. Therefore, including multiple measurements protects you from using an insensitive measurement method

If done right, most standard characterization on piezoelectric transducers can be automated. My opinion is that it is a wrong methodology to seek the minimum number of measurements.