On Monday 06 July 2015 07:00:00 andy pugh wrote: > On 6 July 2015 at 11:06, Gene Heskett <[email protected]> wrote: > >> Well, you _could_ spend much longer hand-winding your own > >> large-bore resolver to get an even better and tougher transducer > >> :-) > > > > Yes, I could, but I know zip about how those work. URL for a decent > > tut? > > It wasn't a particularly serious suggestion. It ought to be reasonably > easy to make a resolver. But making one that gives a linear > relationship between angle and output is likely to be very hard, and > that is probably what makes them so terribly expensive. > > http://www.amci.com/tutorials/tutorials-what-is-resolver.asp
This one is easy enough to understand, the precision is in the angular positions of the coils. Calibration would consist of setting the gain from each coil so they exactly match in peak outputs, the rest is phase angle comparisons. 5 degree accuracy from the junk box. .05 degrees and you'll need to bring a little red wagonload of tenners. > You could obtain very similar feedback from two analogue proximity > sensors at 90 degrees and an eccentric target. I would think, on the face of it, that 4 such sensors would be needed, because of a need to cancel the square law effect in a single ones output so you use 2 at 180 degrees and another pair facing each other 90 degrees away? The only devices I can think of that would not be subject to that would be an extremely sharp pulse laser that measures the time to the returning echo, which at the distances used for this, would be in small fractions of a femtosecond. That would push the state of the art and cost real money. Even in RF testing, looking for transmission line defects, for a 5000' range out and back, a Time Domain Reflectometer costs 10 grand or so. And yes, I have made and used the poor boy equ from schotkey ttl logic and a fast scope, which was good enough to tell the tower crew where to start tearing open a feedline full of burnt teflon below a failed connector bullet. And I hit it right on the mark, probably more from serendipity & SWAG from looking at the scope than the ultimate accuracy of the test setup. The scope was only a 100 mhz scope so asking that display for inch accuracy wasn't possible. Nearest 10 feet or so. The line is in 20 foot pieces. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Don't Limit Your Business. Reach for the Cloud. GigeNET's Cloud Solutions provide you with the tools and support that you need to offload your IT needs and focus on growing your business. Configured For All Businesses. Start Your Cloud Today. https://www.gigenetcloud.com/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
