[Test-Equipment] Ideas ?

[George Shaw]

I thank you for the ideas so far but let me explain a bit further. The
relays are all British Rail specification relays in an interlocking =
relay
room controlling signals and points for Belfast Central Station and =
beyond.
We can NOT break any cables to make any sort of connection nor can we =
attach
direct to the coils or cases of the relays. What we have done so far is =
to
use a spare contact (front or back NO or NC) that mimics the contacts we =
are
monitoring feeding it with 24V DC and logging the change in state from =
open
to closed (+24V present to 0V present at date logger channel input) the
relays are all DC.

We do not always have a spare contact and are not allowed to connect
anything into the lines that carry any control signals to the network. =
The
only way we can do this is to attach some sort of device that will clip =
onto
existing cable somewhat like a clamp meter induction clamp. We only need
this device to:

1. Sense the presence or not of a current (DC) and switch a 1v to 24V
current to the data logger. (+V =3D Bit 1 ON - 0V =3D Bit 0 OFF)

2. Allow non-contact or non-intrusion connection to the cable.

4. Be economic enough to allow several hundred to be used, the idea =
being to
attach them and leave in place. Or at least 38 per relay room at a time =
on a
semi-permanent bases.

5. Themselves NOT to introduce any AC or any interference with the =
cables
they attach to.


--
George Shaw MI3GTO

" Any Sufficiently Advanced Technology
is Indistinguishable from Magic"
                          ---Arthur C. Clarke

Mobile: +44 (0) 7740 361 163
Email: george.shaw@ukf.net
Fax & Voicemail: +44 (0) 871 242 9183