Please refer to the diagram below for correct Modbus network layout:Įxact method for cable termination and conductor landing of Modbus networks will vary depending on whether or not device termination points possess independent DC REF/ COMMON and SHIELD/GROUND landing terminals. Devices identified by DECK Monitoring Engineering as inducing noise into the Modbus network shall require each require one (1) approved RS-485 Optical Isolator.Network wiring shall be executed with cable approved by DECK Monitoring.Network shall include cable termination per Modbus protocol specifications.
Network shall originate from a single Bus Master device.Devices shall be networked as a single bus.Please refer to the table below for cable recommendations from DECK Monitoring:ĭECK Monitoring recommends that you observe each of the following standards for network wiring: We recognize that environmental noise at some project sites can lead to issues that may require additional hardware and labor.
The items in this document are presented as points of interest to designers and installers of Modbus networks.ĭECK Monitoring recommends this cable and network wiring method in an attempt to provide a stable bus for Modbus RTU communications. Many of the more common problems associated with RS485 network stability can be mitigated by following these recommendations for wiring, termination and line bias. Engineers at DECK Monitoring have reviewed information from many sources to create the following recommendations for a standard and robust wiring method. Several cables and wiring methods are referenced by installers when deploying Modbus communications networks. Installation andĮlectrical wiring should be done by a licensed electrician who has experience working with energy monitoring equipmentĬable Termination (RS485/Modbus RTU Line Termination Resistor)Ĭable Termination (RS485/Modbus RTU Line Bias) Overview If you need to isolate all communication wires please see our 8-wire optical isolator.This document from DECK Monitoring suggests Engineering Standards for RS-485/Modbus RTU network wiring.ĭECK Monitoring provides information about installation in good faith, but DECK is not responsible for installation. This is a 3-wire isolator which means that it protects the TX, RX and GND communication wires. The port powered feature of this isolator means that you do not need to connect an external power supply to the unit, it gets its power from the RS232 port, it can do this effectively without interfering with the data communication. One isolator at each end of your communication wire is recommended if the communication distance is longer than 100 feet, however the recommended distance depends on the amount of static electricity in the surrounding environment. The isolator is easy to connect, simply connect it with the DB9 connectors between your communication wire and your device.
It effectively protects your RS232 devices for up to with 1500V constant voltage, 600W surge protection and 15KV ESD static protection.
If you need to effectively protect your RS232 ports and devices against high-voltage spikes, surges, ground-loops and other damaging voltages then this optical isolator is what you need.
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