4-20mA sensor driver 05701-A-0283

Typical Loop Powered Detector Connections

Loop powered detectors (e.g. most smoke, heat and manual call points) have two wire

connection. The detector documentation will indicate the positive and negative loop

connections. Multiple detectors may be connected in parallel on a single loop input provided

the loop operational limit for quiescent current is not exceeded.

At the System 57 end of the field cables, the two detector wires should be connected to the

appropriate channels IN+ and IN- terminals of the Hex Relay Interface Card that is attached

to the required 5704F Control Card. The loop current always flows from the IN+ terminal and

returns via the IN- terminal.

For fault monitoring purposes an end of line (EOL) resistor must be fitted in or after the last

detector on the loop. The typical value for end of line resistance is 5.1k ohms.

The detector cable screen, or steel wire armour or braid as appropriate, should be

connected to the system protective earth. This can be achieved where the cable enters the

cabinet by using a metal cable gland, or by other suitable means, and avoiding any screen

tails within the cabinet. Where the cable consists of a separate screen sheath and wire

armour or braid, the armour should be connected at the cabinet entry to the protective earth

and the screen sheath should be connected to the GROUND terminal of the Hex Relay

Interface Card or to a suitable instrument earth point.

Typical Loop Powered Detector with IS Barrier Connections

Loop powered intrinsically safe detectors (e.g. most smoke, heat and manual call points)

have two wire connection. The detector documentation will indicate the positive and negative

loop connections. Multiple detectors may be connected in parallel on a single loop input

provided the IS criteria and loop operational limit for quiescent current are not exceeded.

In the safe area, the two wires from the detector should be connected to the field (hazardous

area) side of the barrier. The input (safe area) side wires from the barrier should be

connected to the appropriate channels IN+ and IN- terminals of the Hex Relay Interface

Card that is attached to the required 5704F Control Card. The loop current always flows from

the IN+ terminal and returns via the IN- terminal. The barrier must be earthed appropriately.

For fault monitoring purposes an end of line (EOL) resistor must be fitted in or after the last

detector on the loop. The typical value for end of line resistance is 5.1k ohms.

When using an external barrier the IS compatibility link for the input must be set

appropriately. Intrinsically safe systems must be earthed at one point only. All detector cable

screens should be connected separately to the IS safety ground.