[Test-Equipment] Ideas ?

Sat, 6 Sep 2003 22:01:32 +1200

Provided you can break the circuit for each relay coil briefly, a possible
solution would be to use hall effect 'slide on over existing wire" type
devices- these are available in a range of types and physical sizes.
Depending on the type used, these transducers ( really current transformers)
can either give you the actual current in the relay coil or merely produce a
logic level corresponding to a preset current threshold being exceeded or
otherwise- for DC and/or AC.  Clipon devices are also available but probably
too expensive and not necessary for this permanent(?) application. Find your
nearest LEM (european outfit) agent/ distributor and check out their range
of devices. There are others as well but this is one I was checking out
recently for a similar application.

Dave Brown, ZL3FJ
Christchurch, NZ

----- Original Message ----- 
From: "George Shaw" <[email protected]>
To: <[email protected]>
Sent: Saturday, September 06, 2003 9:54 AM
Subject: [Test-Equipment] Ideas ?

Folks

I am looking for ideas for the following, and of course though some of you
would have a few ideas.

I need to attach a Data Logger device to a series of relays. There is not
always spare contacts on the relays and I can NOT add wires to the existing
relays. The logger simply records change of state form say de-energised to
energised (open-closed, picked-dropped, No - Nc, power on power off)
switching at the moment via the negative wetting voltage supplying spare
contacts that mirror the actions of the ones being monitored.

I am looking for a Cheap induction type clamp on device (up to 38 channels
need to be monitored so each logger will require 38 of the devices). The
inputs to the logger are + and - with logging taking place when a voltage is
applied or dropped (+ V detected = Bit 1,  - V detected bit 0 change from
bit 1 to 0 = change in state). I am happy to build such devices or to
purchase if cost is within reason.

Any ideas or products/designs circuits welcome.

--
George Shaw MI3GTO

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

Mobile: +44 (0) 7740 361 163
Email: [email protected]
Fax & Voicemail: +44 (0) 871 242 9183

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