>> I'd suggest trying rate of change of velocity. > What a great idea! And here we were all wasting time talking about > measuring accelleration. One could reasonably infer, with a prospect of being in error, that he meant rate of rate of change, which may well be useful. RM -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist