Delta Network Sensor: BACstat I DNS-14 (Rev 1.6) Installation Guide
Page 4 of 12
Document Edition 1.9
Mounting
The DNS-14 backplate is designed for mounting directly on a standard North American electrical box, but
may be mounted in other ways as well.
Power
The DNS-14 BACstat requires a 24 VAC @ 2 VA power supply, typically an isolated Class II transformer.
More than one device – not including DCUs or V2 products – may be connected to the same transformer,
providing the transformer is properly sized, including line losses, and polarity is observed between controllers
(in regards to 24~ and GND). The transformer must
ONLY
be used to provide power to other MS/TP
or
LINKnet devices. Auxiliary field devices (i.e., 4-20 mA devices) that don’t use ½ wave rectification must be
powered separately.
Network & Cabling Requirements
To ensure network stability and reliable communications, particularly at high speeds on the RS-485 MS/TP or
LINKnet networks, it is imperative that you adhere to the following network and cabling requirements:
Item
Description
Cabling
For MS/TP and LINKnet networks it is recommended that you use network cabling that
matches the following specifications:
•
Balanced 100 to 120 ohm nominal impedance Twisted Shielded Pair (TSP) Cable
•
Nominal capacitance of 16 PF/FT or lower
•
Nominal velocity of propagation of 66% or higher
Topology
For MS/TP and LINKnet networks, ensure the cable is installed as a
daisy-chain
from one
device to the next.
Max. Nodes
•
MS/TP: The maximum number of devices per MS/TP network without any repeaters is
50
.
•
LINKnet: The maximum number of devices per LINKnet network is 12, depending on the
Application Controller used. Refer to Appendix G in the
Technical Reference Manual
.
Termination
Boards
•
MS/TP: A termination board (TRM-768)
must
be installed at each end of each MS/TP
network segment – or two per MS/TP or LINKnet network. Ensure you do not overlook this
in laying out your network architecture and ordering product.
•
LINKnet: Termination boards need not be installed for only one or two nodes.
However, install a termination board on each end of the network when there are more
than 2 nodes.
Repeater
•
MS/TP: A repeater (RPT-768) is not necessary unless more than 50 nodes will be installed
on a network
or
you need to extend the network beyond 4000 ft (1220 m).
•
LINKnet: Repeaters should not be necessary. Ensure the maximum distance is no
more than 1000’ (300 m).
For more detailed information, including wiring, refer to the RS-485 Network Installation Guide (DOC818-11).
