> Of Ma Be > I feel quite strongly that rpm is also another... "idiocy" we could do > without
I got my second degree in a sound and vibration institute: http://www.human-vibration.com/HFRU_pages/hfru.htm Hertz was part of everyday speech. The only difference between Hz and rpm is that the second is the base for one and the minute for the other. Since the second is an SI unit, that puts the Hz above rpm. You can almost directly perceive the Hertz value for ship motion simply by counting. I can't think of an example where an rpm value can be directly perceived because a minute is too long. People are quite happy discussing 50 Hz for mains electricity. We had to deal with it as interference with our data all the time, I can't imagine discussing 50 Hz as an rpm value (although that is a good old conversion issue). Of course, using Hz means that there is a seamless integration with high frequency applications like radio. I have often thought that car rpm meters should be in Hz. Having said that, I think Hz is an unnecessary unit and might be better replaced with inverse seconds i.e. s-1 (with the correct superscript). -- Terry Simpson Human Factors Consultant [EMAIL PROTECTED] www.connected-systems.com Phone: +44 7850 511794
