Post by thread:OT remote monitoring

Hi, folks. What is the best way to keep track of a 0-24V instrument from a distance of 2 miles (approx. 3 km) ? I have wires from point to point, already. Well, I have a PLC at the monitoring station, but I guess I can't help but add some treatment to the signal at the source and then send it digitally. What is the max. distance for a RS-485 interface ? Am I forgetting something ? Best wishes, Pedro.

I think most here would want to know your data rate (i.e. how many bits of resolution are you reading with, and how often?) Sounds a LONG way for RS-485, perhaps current loop (Ick, I know <G>) if slow enough baud rate here? Also using a "Leased Line" modem pair would perhaps work, if you can find good modems for the job (ZyXEL's did it for me, once.) What's cheapest, would take more data for an optimized answer here. Mark Pedro Drummond wrote: {Quote hidden}> > Hi, folks. > > What is the best way to keep track of a 0-24V instrument from a distance of > 2 miles (approx. 3 km) ? I have wires from point to point, already. Well, I > have a PLC at the monitoring station, but I guess I can't help but add some > treatment to the signal at the source and then send it digitally. What is > the max. distance for a RS-485 interface ? Am I forgetting something ? > > Best wishes, > > Pedro.

Yes, well data rate is not a problem, I will need to update the reading once in a while. So I can send it as slow as I have to. Do any of you have links to current loop modems ? Thanks a lot. Pedro. At 07:04 15/01/99 -0700, you wrote: >How about short-haul modems? I think thats what they are...BlackBox makes >some I believe. > >

One pair was on eBay for $25 just yesterday, lessee: cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=54966416, contact spam_OUTjtyoungmanTakeThisOuTaol.com, these didn't sell so I presume he'll re-list them? If not, B&B [http://www.bb-elec.com/welcome.html] usually has this sort of thing, at semi-reasonable pricing, also Black Box [http://www.blackbox.com/]. B & B Electronics wants about $40 USD apiece for these, see Page 11 of their catalog (It's downloadable as a .PDF file.) They also want $15 for the power supply, which you may not want to pay <G> Theirs are already opto-isolated (You want optoisolation, for a 2-3 km long line! You knew that already though <G>) (I'm paranoid, maybe, but I'd have lightning rods at each end - if appropriate <G> Mother Nature is pretty powerful...) Black Box: See page 524 of their catalog, the # ME739 series is what I suspect MIGHT work, but these are transformer isolated not opto-isolated, and they want $170 apiece for these, so think B & B maybe <G> Mark Pedro Drummond wrote: {Quote hidden}> > Yes, well data rate is not a problem, I will need to update the reading once > in a while. So I can send it as slow as I have to. > > Do any of you have links to current loop modems ? > > Thanks a lot. > > Pedro. > > At 07:04 15/01/99 -0700, you wrote: > >How about short-haul modems? I think thats what they are...BlackBox makes > >some I believe. > > > >