Hi all,
I would like to know why an End of Line (EOL) resistor is used. How do I connect it to a safety system (deluge system) solenid valve. I am made to understand that it is used for line fault monitoring. What device would be required for this in the control unit? I intend to use ABB DCS to connect the soleniod in remote operation.
Is there any site where I could get more details on this?
Thanks in advance
Jacob

 

This is my understanding: An EOL is used in a 'supervised' circuit to establish a known current value. A monitoring circuit/device then can detect a change to either a shorted or open condition and generate an alarm.

Don't have any idea how to connect it to your application.

Try 'alarm circuit monitoring' or something like that in Google.

 

An end of line resistor is normally used to terminate a communication line. For example, a Device Net comms line to 7 devices. An end of line resistor is turned on at device 3. The Device Net scanner will only see devices 1, 2 and 3. The remainder of devices will be blocked from view by the scanner at the point of the end of line resistor.

 

First question is what you want to accomplish? Then find out what is needed to do the job.

Overall need will be a "FAIL-SAFE" design, so that any equipment or wiring failure immediately known or "alarmed" and fixed before an emergency arises requiring deluge etc.

 

At first I thought your post referred to bus termination resistors. In this application, the function of the resistor (which is the same value as the nominal impedance of the cable) is to suppress signal reflection by dissipating the signal current at the end of the wire and making the cable appear to be of infinite length.

In a fire suppression system, the function of the end-of-line resistor is different. The resistor is placed across the two sensing or actuating
conductors, thus forming a loop. A very small current is passed through the loop so that the central fire control system can monitor the current and continuously verify the integrity of the wiring.

 

NFPA 72 covers this.

Jeffrey D. Brandt
Carpenter Engineering, Inc.

 

Hi all,

Monitoring of circuits with EOL resistors can be done using an analogue input on the PLC. Just set up the the monitored circuit as part of a voltage divider and use the analogue input to measure the voltage. Then program condition statements to determine normal, alarm and fault conditions. In security circuits, 2 EOL resistors are often used (1 in series with the contact and 1 in parallel) which allows for detection of both open and short circuit faults (or tampering) as well as normal and alarm conditions.

Regards

Peter Whalley

 

In a former life, I received a patent on an EOL device that detected, and diagnosed, three faulted conditions... open-circuit, short-circuit
and ground-fault. If you are interested, let's talk!

Regards,
Phil Corso, PE
Boca Raton, FL
( TAL-2 @webtv.net )

 

if we measure the voltage acrosse the EOL and suppose some smoke detectos we have at our fire alarm system (cerberus) are missing .Are we going to have any change in the reading.
Please answer me .I think I understood the hall subject but I have little confusion .

THANKS