Another sensor they use in precision hydraulic cylinders is the Temposonic magnetostrictive transducer. These can be obtained in almost any length. They send a pulse down the element and sense a return pulse from a ring magnet that is attached to your moving component. The longer the stroke the longer the return delay, so your sample rate has to drop for long strokes. The have a variety of analog and digital outputs available.
I see several listed on ebay at the moment. This is one: http://www.ebay.com/itm/190623239746 (12" stroke, not 1m) This may not be low enough cost for your application, but long stroke lvdt's are pretty expensive too, and I suspect difficult to fabricate to high linearity. -- Ralph ________________________________________ From: Leonardo Marsaglia [leonardomarsagli...@gmail.com] Sent: Monday, August 13, 2012 4:48 PM To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] CNC Grinder Hello Andy. That's really good news, if one can use a DIY LVDT that would reduce the cost drastically. I've only seen low travel LVDTs intended to be used in diameter measuring and things like that. Do you think a 1000 mm LVDT is possible to accomplish without great issues?. Thanks! Leonardo. 2012/8/13 andy pugh <bodge...@gmail.com> > On 13 August 2012 21:30, Leonardo Marsaglia > <leonardomarsagli...@gmail.com> wrote: > > > We've had always the idea to replace the pistons with a ballscrew and > servo > > motor, mostly because of the hydraulic system maintenance. But watching > > what you've done this seems a lot cheaper and with less work than > replacing > > all the hydraulic systems. > > I used to run a servo-hydraulic fatigue testing machine. That used an > LVDT and a Moog valve to give very precise position control. It is > definitely an effective technology. > > -- > atp > If you can't fix it, you don't own it. > http://www.ifixit.com/Manifesto ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
