What is a Piezo Transducer?
Dear Labby,
Can you give a little detail to the piezo transducer and it’s operation? How does it function? Where would you screw it into on the M1 Garand. The AR-15? The 1911?
Thanks,
Bill M.
Bill,
Black arrow indicates transducer location during testing.
The bottom of the piezo is cut to match a case’s body. The threaded end is connected to the pressure gauge.
The first image is of a piezo transducer in action as part of regular testing. In the American system, the transducer’s base is radiused to match the case body. When the cartridge is fired, the case expands crushing the piezo which creates a spark, the intensity of which can be directly translated into PSI. In the Garand, the lab used a modified gas plug to get the port pressure readings. Chamber pressure testing was done in a standard pressure barrel. For AR 15 military testing, a transducer is mounted at the case mouth and another at the point where the gas block would sit on the barrel. 
The 1911 , a delayed blowback, doesn’t have a gas system. Testing for that type of pistol would rely on cartridge pressure testing from a test barrel.
The Lab