On Sun, 20 Dec 2009, Kenneth Lerman wrote: > Date: Sun, 20 Dec 2009 10:54:46 -0500 > From: Kenneth Lerman <kenneth.ler...@se-ltd.com> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > Subject: Re: [Emc-users] Interferometric leadscrew measurement/mapping? > > Yes, I have an Agilent 5517D which is a frequency stabilized two > frequency laser that I got on Ebay. > > How fast can the counters on the 5I20 count? I would need a pair of > perhaps 32 bit counters that can count at more than 4 MHz and can be > read out "simultaneously". (Actually, copied into another set of > registers at the same time and then transferred to the host before the > next copy time). > > Ken
The counters will count fast enough but with hostmot2 they are only 16 bits wide (This should not be a problem at 4 MHz as the rollover rate would only be 64 Hz and servo thread sampling would likely be at 1 KHz or more). Its possible to latch both counters simultaneously with the index (or probe) input so seem like you could do what required. Probably better would be to add a HostMot2 module for interferometer counting, with common reset, 32 bit counters (maybe with difference available) and perhaps a relative phase register, (at 100 MHz sample rate you could get ~15 degrees resolution of you 4 MHz reference) I would not mind doing the firmware (probably no more than a couple hours work), but the HostMot2 driver would need to have support added for the special counter > > Anders Wallin wrote: >>> A laser interferometer is on my todo list. I've acquired all of the >>> optics on ebay for a total of a few hundred dollars. I've built a power >>> supply. The major part I'm missing is the counting and interpolating >>> electronics with a computer interface. >>> >> >> Hi Ken, >> >> the heterodyne interferometers I have found described mostly use a >> two-frequency laser which emits two orthogonal polarizations with >> slightly (500kHz? or in your case 4 MHz) different frequency. Did you >> find a Zeeman-stabilized two-frequency laser on ebay? Or are you >> planning to DIY and put magnets around a normal HeNe tube? Sams Laser >> FAQ has a description: >> http://www.repairfaq.org/sam/laserchn.htm#chndzees >> >> The other method is to use an acousto-optic modulator to shift the >> frequency of the light. But the papers I've found use two modulators, >> and I only have one to spare right now... >> >> If I can either find a two-frequency HeNe or DIY with magnets then I'd >> be interested in testing this, possibly with the m5i20 (already has >> fpga code for fast encoder counters) for data acquisition. >> >> Anders >> >> ------------------------------------------------------------------------------ >> This SF.Net email is sponsored by the Verizon Developer Community >> Take advantage of Verizon's best-in-class app development support >> A streamlined, 14 day to market process makes app distribution fast and easy >> Join now and get one step closer to millions of Verizon customers >> http://p.sf.net/sfu/verizon-dev2dev >> _______________________________________________ >> Emc-users mailing list >> Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users >> > > ------------------------------------------------------------------------------ > This SF.Net email is sponsored by the Verizon Developer Community > Take advantage of Verizon's best-in-class app development support > A streamlined, 14 day to market process makes app distribution fast and easy > Join now and get one step closer to millions of Verizon customers > http://p.sf.net/sfu/verizon-dev2dev > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ This SF.Net email is sponsored by the Verizon Developer Community Take advantage of Verizon's best-in-class app development support A streamlined, 14 day to market process makes app distribution fast and easy Join now and get one step closer to millions of Verizon customers http://p.sf.net/sfu/verizon-dev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
