From: "Terrell W. Fritz"
Date: Sat, 30 Dec 2000 09:50:15 -0700
Subject: Re: [TSSP] NSVPI - Latter Results
Hi Paul, Wow! This is surprising! I thought the jitter was me ;-) It is very likely that I vary by +-1 turn in the tap points and the area between 5 and 10 inches is were the space windings slipped once and the variation there is easily more. However, I did note the that repeatability was good. In light of your new analysis, it looks like I did as good as could be expected. This is the kind of things computers are great at! They can make curves and graphs nice and smooth and then allow one to find the effects of various "noise" without having to worry about any other factors being involved. Thanks for doing this. It gives be much great confidence in this type of testing now knowing that it seems to work well given the inevitable real world constraints. Cheers, Terry At 10:13 AM 12/30/2000 +0000, you wrote: >Terry, > >I'm now beginning to process (again) the NSVPI results, both >the new toroided data, and the existing bare coil data. > >I noticed something that you may find satisfying, concerning the >'jitter' in your measured gradient readings. > >When I printed out the 'predicted' curve on the original graphs, >the gradient is calculated on a turn-by-turn basis, which gives >a nice smooth curve. Against this smooth curve, your measurements >were up and down, see > > http://www.abelian.demon.co.uk/tssp/pn2510/nsvpi2210b.gif > >for example. > >I decided to try comparing the data differently. Instead of >printing out the predicted curve turn-by-turn, I calculated the >voltage differences at 1" intervals, since that is what you were >measuring. > >Unfortunately, 30 into 1000 doesn't go - in order to apply the >probe you have to select the nearest turn. The result is a jitter >of +/- 1 turn at each end, a possible variation of +/- 2 turns in >an average 33.33 turns per inch. > >If I calculate the gradient in 1" steps, the calculation has to >pick the nearest turn in the same way as your probe did, and guess >what - the same jitter appears, and at the same amplitude. > >I've compared your original bare coil measurements with my 1" gradient >predictions in > > http://www.abelian.demon.co.uk/tssp/pn2510/nsvpi-jitter.gif > >The conclusion is clear - your NSVPI measurements are probably much >more accurate than previously supposed and the apparent jitter is >caused by the necessity to 'quantise' to the nearest turn. > >Cheers, >-- >Paul Nicholson, >Manchester, UK. >--
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.