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
Re: gEDA-user: OT - non-contact digital current loop sniffer
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
Re: gEDA-user: OT - non-contact digital current loop sniffer
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
