Allen-Bradley micrologix 1500, Руководство пользователя

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Publication 1764-UM001A-US-P
Understanding Communication Protocols E-11
Important DH-485 Network Planning Considerations
Carefully plan your network configuration before installing any hardware. Listed
below are some of the factors that can affect system performance:
•
amount of electrical noise, temperature, and humidity in the network
environment
•
number of devices on the network
•
connection and grounding quality in installation
•
amount of communication traffic on the network
•
type of process being controlled
•
network configuration
The major hardware and software issues you need to resolve before installing a
network are discussed in the following sections.
Hardware Considerations
You need to decide the length of the communication cable, where you route it, and
how to protect it from the environment where it will be installed.
When the communication cable is installed, you need to know how many devices
are to be connected during installation and how many devices will be added in the
future. The following sections will help you understand and plan the network.
Number of Devices and Length of Communication Cable
The maximum length of the communication cable is 1219m (4000 ft). This is the
total cable distance from the first node to the last node in a segment. However, two
segments can be used to extend the DH-485 network to 2438m (8000 ft). for
additional information on connections using the AIC+, refer to the
Advanced
Interface Converter (AIC+) User Manual , publication 1761-6.4.
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