Quote: (Originally Posted by
Sutty)
I was thinking more of an add-on to existing units.
Interesting they don't work in helium - most piezos work at resonant frequency - this would probably change in a helium atmosphere, maybe thats the reason.
Neil
Piezos actually fail completely. That is, they do not work normally in air afterwards. Very odd phenomenon. Easy to demonstrate with things like piezo disks used for speakers, or piezo microphones. Problem also affects piezo resistive pressure sensors.
As I said, I do not know the physical cause.
I will post an example helium compatibility report onto our web site sometime next week, explaining how we screen components to helium sensitivity, showing what we tested and the results. We have repeated tests on piezo parts many times, always with the same result. The only things that get through are sealed from the helium, such as crystal oscillators. This problem makes it important to use multiple oscillators in a diving system for processor clocks etc.
Alex
Edit: Report on helium susceptibility of components posted onto the Design Verification section of
OR portion of DL site