On Tuesday 01 January 2008, Colin F. MacKenzie wrote: >A simple voltage divider on any inputs greater than 10v will work fine. >If you mean voltage divider as a kind of voltage supply regulator then >no, don't do it. Most especially ADCs. I also assume you are not talking >about sampling audio with this ADC but data acquisition? Audio sampling >needs to be done with a real codec IC. Standard ADC's sampling audio are >really poor quality due to aliasing artifacts and other issues. The >difference between say a burr-brown pcm codec (audio) and the ADC's you >mention are *clearly* heard, speaking personally. > >Btw: The impedance of the ADC input can slightly affect the value of the >voltage divider. You can find the impedance in the datasheet and adjust >your ladder if needed...in most cases the impedance is negligable for >most people. Also, lower overall impedance of the dividor will make the >ADC input impedance more negligable, but will draw more power. 5-20k is >prob suitable. > >I am not sure what kind of distance sensing could be done, but I am >interested in it too. I think sonic wouldn't be accurate enough.
I think that depends on how you want to use it. For sensing fixed distances like limit stops, and given enough distance to the reflector so the receiver isn't still saturated by the transmit pulse, I believe one could expect and get 0.001" accuracy in air, or maybe 0.0001" in water as the medium. But for short range measurement of an arbitrary 0.0001" anyplace in a 30" x tables motion, no. Too non-linear until you get out to impractical distances. >Laser >would but I don't know how to do that yet, but sounds awesome. ;) A laser, used as an echo sounding device, will tend to suffer the same accuracy problems the sonar would, although I believe the technology itself is farther along than the sonar stuff, which for the most part progress stopped at decent fish finding. Now if a two color interferometer could be built from a two-tone beam, accuracies would far exceed what we could machine to with normal machinery that wasn't being directly controlled by it. This might be an interesting path to investigate, where the relative phases of the two beam colors as reflected from a moving mirror on the table could be used as an index of sorts into a phase angle to linear piece of math that once zeroed, would be capable of tracking to angstrom accuracy over many inches of travel. Humm, thinking out loud here, perhaps a dirty multimode low power IR laser (or IR LED, they are inherently dirty) reflected back to an FIR device with filters for the two most prominent 'colors' it generates? I see a speed problem with that as I don't think the FIR's are that fast though. Just a thought. However, if I can imagine it, someone no doubt has a patent on it 5+ years old and you can buy his version for lot$a bucks. Sigh... :( >Anything else? I know many people are just using bump probes to do 3d >scanning. --- simple and digital. That's what I've done with a very simple optical probe that one of the fellows here gave me a link to the howto build it a year or so ago. Only for tracing large arc surfaces to maybe 15 degree angles off the X/Y plane for that one though. X/Y stability/accuracy is determined by the sliding tubes, maybe 0.010" at best. >C > > >-----Original Message----- >From: John Thornton [mailto:[EMAIL PROTECTED] >Sent: Tuesday, January 01, 2008 8:18 AM >To: [email protected] >Subject: Re: [Emc-users] Emc-users Digest, Vol 20, Issue 52 > >Hi Kirk, > >For the single channel ADC do you have a chip picked out? I think that >I'll just use the MAX186 in the article and ground the unused inputs >unless >you have a better one. A quick google search and it seems to be used a >lot. > >Nosing around on Maxium's site I found some chips that take 0-10v like >this one >http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3998 >Do you think it could be used? If you could hook an analog sensor to >something >like this then WOW! Distance sensing and more... > >Does a simple voltage divider circuit sound good enough to scale the >voltage >down to what the chip needs? > >I'm familiar with C, and just found the comp tool. I'll see what I can >figure out... > >This is kinda new ground for me so any tips would help... > >Thanks >John > > > >------------------------------------------------------------------------- >This SF.net email is sponsored by: Microsoft >Defy all challenges. Microsoft(R) Visual Studio 2005. >http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ >_______________________________________________ >Emc-users mailing list >[email protected] >https://lists.sourceforge.net/lists/listinfo/emc-users -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Old programmers never die, they just become managers. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
