Path: utzoo!utgpu!watmath!att!tut.cis.ohio-state.edu!ucbvax!hplabs!hp-pcd!hplsla!tomb From: tomb@hplsla.HP.COM (Tom Bruhns) Newsgroups: comp.sys.amiga Subject: Re: Weighing Platters Message-ID: <5160051@hplsla.HP.COM> Date: 14 Aug 89 16:49:14 GMT References: <625@orange6.qtp.ufl.edu> Organization: HP Lake Stevens, WA Lines: 23 sutherla@qtp.ufl.edu (scott sutherland) writes: > Lots of other stuff deleted, but this caught my eye: >6) Let the weight of the platter be ~ 3 oz, or ~ 400 g. (I don't have any > idea if this is a reasonable guess for the platter weight.) It's not a reasonable conversion! 1 oz is about 28 grams. > > >7) Then the weight of the platter without lubricant is 400.0000g and > the weight of the platter with lubricant is 400.0004g. Thus you > are trying to measure one part in one million by using the > difference between two large numbers. This is a statistical > nightmare! (Any statisticians care to comment?). If the error > in your scale is 0.0002g, you have a 50% error in your > measurement. NOT GOOD. I don't think it's the measurement that's a problem. Clearly, you'd use the same balance for both the "before" and "after" measurements. Rather, it's making sure that nothing else of similar mass is transferred on or off the platter between weighings.