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

[Stephen Ecob <silicon.on.inspiration@xxxxxxxxx>]

On Thu, Jul 14, 2011 at 1:18 AM, David C. Kerber
<dkerber@xxxxxxxxxxxxxxxxxxxxxxxxxx> 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.


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