From: "Dave Johnson" > At 10:09 PM -0700 8/24/01, Ned Seith wrote: > >As I have worked with accelerometers for a few decades conducting = product > >vibration and shock reliability tests, I was perplexed at the notion = that an > >accelerometer would be deployed as a "Tilt-o-meter" or as a position = sensor. >=20 > They make fine tilt-o-meters, actually, always measuring wrt gravity > pulling "down" (tilt one slowly and watch the output as the gravity > vector tilts relative to the sensor). In fact, here's a page showing > how to modify your Palm computer to play a rolling ball game by just > tilting it: >=20 > http://bodotill.suburbia.com.au/adxl202/adxl202.html >=20 > Dave Johnson Except in the case of aircraft in flight, which is the topic of = discussion. In coordinated flight, "down" is always relative the the = aircraft, and NOT the earth, even in a turn. Ever notice that when on = an airline, contrary to apparent logic, that your drinks don't spill = when the plane banks? The lift generated by the wing is "up" relative to the airframe (and = wing). In a turn, this lift is divided between maintaining altitude = (overcoming gravity) and pulling the plane into the turn (overcoming = inertia, or "centrigugal force", as the plane would rather keep going in = a striaght line). =20 The net result of these forces is a vector >g pointing straight down = relative to the aircraft. the increase in force is relative to the bank = angle... in a 30 degree turn it is about 1.5g, in a 60 degree bank it is = 2g, etc. This is called load factor. So the accelerometers would not be able to detect the "tilt" of the = aircraft. At best, a force >g would be detectable, but no further = directional information (such as where "down" really is). Again, this = only applies to level coordinated flight. Slips, skids, changes in = altitude, etc., will throw this off. I probably didn't explain this too well, hope you get the idea... Actually, ignore my crummy description and take a look at load factor = here: http://www.americanflyers.net/free/section.asp?cid=3D100&p=3D8 Steve ------------------------------------------------------------------------ Steven J. Devine, President, Consultant, TZOGON Enterprises Incorporated President, EAA Chapter 136 (Merrimac Valley) http://eaa136.tzogon.com steve@tzogon.com HAM Tech lic: N1YZJ http://www.tzogon.com ------------------------------------------------------------------------ -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads