Thanks William for that criptic annalysis, although I have no idea what you said i have gathered from some of the other replies that this appeares to be a phenom of unexplained origin and thankfully it does not happen frequently. I did however get rid of the little bugger by turning the digiflex off then on again and got three good consistant readings in succesion.
-----Original Message----- From: william kievit [mailto:[EMAIL PROTECTED] Sent: Wednesday, November 05, 2003 11:40 AM To: [EMAIL PROTECTED] Subject: Re: ShopTalk: ascending frequency readings??? My guess is that you are measuring a hysteresis (internal friction) effect. This is not uncommon in spring analysis. The losses are due to friction at the molecular level. Plated surfaces also introduce hysteresis to a system. The greater the displacement the greater the loss and reduction in natural frequency. Sorry for the technical nature of this reply. The bigger question may be, What is the true frequency? Is it when the displacement is close to the the size exhibited during a swing or is it the higher value measured with our frquency measurement equipment at much smaller displacements? Does the % error actually matter? Bill Kievit John Kaufman <[EMAIL PROTECTED]> wrote: Hi Jim, I did some rather "anal" testing on shafts for an article I wrote for the PCS Journal earlier this year. I ran into the same problem. The more I twanged the shaft the higher the frequency. This was with a Club Scout IV which reads to a tenth and the phenomenon was very easy to see. It had nothing to do with the depth of twang just how many times I twanged it. It only seemed to happen with steel shafts. Worried it might be something I screwed up in my analyzer design I tested the same shaft with a friend's Digi Flex and got the same results. I wish I had an explanation but I don't. I got even weirder results when I clamped a steel shaft in a three jaw lathe chuck. Regards, John K ----- Original Message ----- From: Letourneau, Henry J AM1(AW) (VAW120) To: Sent: Tu! esday, November 04, 2003 9:22 PM Subject: ShopTalk: ascending frequency readings??? > HI, I need some help understanding why i get ascending frequency readings > when testing tt dg steel shafts. when i twang the shaft and get, say 230 cpm > then reset and get 231 off of the same twang, then reset and get 232 and so > on untill the shaft wont register. this seams to sugest that the shaft is > speeding up as the oscillation intervals get shorter. any sugestions? Thanks > - Jim _____ Do you Yahoo!? Protect <http://antispam.yahoo.com/whatsnewfree> your identity with Yahoo! Mail AddressGuard
