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Real RS-232 Cable Length Limit

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danielthb

Electrical
Mar 14, 2007
16
175 cable feet of STP between a PC comm port and the DCE--think it'll work at 9600, at 19.2k? I'm not looking for what the specs say but what your experiences are. Cut sheet for the cable says 40pF/ft @ 1.0 MHz.

Dan B
 
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Sure.

Oh..
40pF/foot... That sucks.

Maybe not. If it doesn't, it's your crummy cable.

It's a hard call really as it also depends on your electrical environment. I would imagine 9600 would be dependable. Maybe 19.2k with good cable. In a benign place.

Hopefully you are driving the cable with nice levels not some laptop with +/- 3V levels.

Keith Cress
Flamin Systems, Inc.-
 
I doubt there's a commercial cable for this service, so your're talking custom cable. That'll cost ? ?

If it's a dollar a foot plus connectors and labor, $200?

What about a couple 232/485 converters, one for each end, and 200' of twisted pair that you've already got lying around, instead? Far higher probability of it working.

Dan



 
If you use this cable spec you can get 500 ft distance. experienced it myself.

Black Box EDDC

but on the - side it is expensive.

 
I believe most of interfaces were at 9600, some were 19200, and never above that speed. bar code scanners usually char length= 20 to 50. sometimes scales, conv speed up to 550 fpm, gap between cases 12-15 inches.
 
I don't think you'll do 9600 at 175' over STP.

Current loop should work okay.



Mike Halloran
Pembroke Pines, FL, USA
 
Well Black box said 500ft.


They don't say at what baud rate. Might be 300. But I think 175ft is possible. I had about 120 feet that we used all the time for various serial endeavors at speeds up to 34,5k and I don't remember having any problems.

Keith Cress
Flamin Systems, Inc.-
 
some applications that I did were up to 400 feet and at 9600 baud as far as I remember. It all depended on main panel location and scanner locations. This was with the black box eddc cable.
 
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