Yes, we have access to a single wire carrying the signal current (I remember enough of my 27-year old EE degree to catch that).
But I had my doubts about a current transformer, because of the chance of having several bits at the same level, either high or low current, not giving any signal; ie a dc current for a short period, causing the signal from the CT to go to 0. ISTM that this case would require some rather extensive signal processing, but I could easily be wrong about that; that's why I was thinking of a hall-effect transducer, which would detect dc signals. Am I worrying about non-issues here? Dave > -----Original Message----- > From: geda-user-boun...@moria.seul.org > [mailto:geda-user-boun...@moria.seul.org] On Behalf Of Andy Fierman > Sent: Thursday, July 14, 2011 3:49 AM > To: gEDA user mailing list > Subject: Re: gEDA-user: OT - non-contact digital current loop sniffer > > As long as you have access to a single wire and not the return path! > > :) > > Andy. > > signality.co.uk > > > > > On 13 July 2011 22:48, Stephen Ecob > <silicon.on.inspirat...@gmail.com> wrote: > > On Thu, Jul 14, 2011 at 1:18 AM, David C. Kerber > > <dker...@warrenrogersassociates.com> wrote: > >> Hi, electronics gurus - > >> > >> We have an application where we need to passively monitor > a digital current loop (no data sending by us), with a data > rate of 9600 baud. We already have solutions for tapping > into the circuit, but in some of our customers' cases the > circuits don't have enough drive capability to add another > load to it. So we're looking for a non-loading, and > preferably non-contact solution, such as a inductive pickup > or hall-effect pickup, that hopefully wouldn't require us to > break into the circuit. > >> > >> Does anybody know of such an animal? If not, it's also > possible that we might contract to have one designed, but > that's not decided for sure yet. It's a fairly electrically > noise environment, but not extreme, and the sensor itself > would likely be installed inside an already-existing box on > the wall. The circuit runs at 45mA for the high signal, and > the low is <2mA. > > > > Is the current flowing through a length of accessible wire at some > > point, or is it only accessible in a PCB trace ? > > If it flows through a length of wire then running it > through a current > > transformer could work well. > > > > > > _______________________________________________ > > geda-user mailing list > > geda-user@moria.seul.org > > http://www.seul.org/cgi-bin/mailman/listinfo/geda-user > > > > > _______________________________________________ > geda-user mailing list > geda-user@moria.seul.org > http://www.seul.org/cgi-bin/mailman/listinfo/geda-user > _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user