Sutron ModbusLink-M Manual

ModbusLink-M/
ModbusLink-S
OPERATIONS &
MAINTENANCE MANUAL
Part No. 8800-1197
Revision – 1.0
April 1, 2013

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Table of Contents
1. Introduction..........................................................................................................................2
Features....................................................................................................................................2
2. Unpacking ...........................................................................................................................3
Unpacking................................................................................................................................3
3. Hardware Description..........................................................................................................4
Connectors ...............................................................................................................................4
Terminal Block ........................................................................................................................5
Battery Connections.................................................................................................................5
4. Setup and Operation...........................................................................................................6
Modbus Connections................................................................................................................6
ModbusLink Network basics...................................................................................................6
Setup ........................................................................................................................................8
Configuring ModbusLink ........................................................................................................9
Optional Mounting Bracket Kit (2911-1395)............................................................10
Quick Start Guide ......................................................................................................12
Verifying Communication...........................................................................12
6. Troubleshooting and Maintenance......................................................................................13
Troubleshooting.......................................................................................................................13
Maintenance.............................................................................................................................13
Appendix A ...............................................................................................................................14
Specifications...........................................................................................................................14
Ordering Information...............................................................................................................14
Appendix B ...............................................................................................................................15
Appendix E– Commercial Warranty.........................................................................................16
SUTRON MANUFACTURED EQUIPMENT .......................................................................16
NON-SUTRON MANUFACTURED EQUIPMENT .............................................................16
REPAIR AND RETURN POLICY .........................................................................................16
EXTENDED WARRANTY AND ON-SITE MAINTENANCE............................................16

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1. Introduction
The ModbusLink is a low power multihop mesh network to wirelessly connect modbus sensor(s) to a
Modbus Master. A ModbusLink network consists of one master (ModbusLink-M) connected to a Modbus
Master/logger/data recorder and at least one slave (ModbusLink-S). Each Slave unit can be connected to one
Modbus sensor via either a RS232 or RS485 port. If the ModbusLink-M is unable to reach a Modbus sensor
directly, it will try to discover a route to the destination via intermediate ModbusLink-S modules.
Features
•300 meters LOS range ( longer ranges possible via intermediate nodes/mesh networking)
•Very low power consumption.
•All nodes are capable of routing messages, interfacing with Modbus sensor while staying in
low power mode
•~5 years battery life (included)
•Transparent drop-in Modbus wire replacement. (No special address requirements)
•RSSI level indication to indicate Signal strength.
•Multiple Networks can co-exist without interfering with each other.
•Simple Network commands to configure & maintain network

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2. Unpacking
Unpacking
Remove the ModbusLink-M and ModbusLink-S units from the shipping container and visually inspect the
unit for signs of damage during shipment. Report any such damage to the factory immediately to ensure a
prompt response and resolution. Retain one shipping container in the event a factory return is necessary.
Please note that if a return is required, a return material authorization (RMA) number is required. To get this
RMA number, call the Sutron Customer Service Department at 703 406 2800.

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3. Hardware Description
Connectors
The ModbusLink-M/S modules support the Modbus protocol (RTU mode) over RS-232(default) or RS-485,
selectable via a simple command. The external IP6 rated DB9 connector should be used for communication
with Modbus loggers/Sensors using RS-232. For interfacing with a modbus logger/sensor over RS-485, a 5-
terminal connector is provided. The module can also be provided external power via the 5 pin connector.
Please refer to Table 1 for a detailed description of the connector.
The ModbusLink modules can be connected to a PC via the 10-pin header J4 using a 10pin to DB9F cable
(6411-1382-24) for configuration/debug purposes.
Figure 1 – ModbusLink ports
DB9 Connector
Modbus ( RS232)
PC Configuration port
8-16v Power input
RS485-A/B
RS485-A/B
Modbus (RS-485)
8-16v Power input
6411-1382-24

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Terminal Block
The ModbusLink modules have a 5 position terminal block that supports plug in screw terminals. The screw
terminals are connected to a 5-wire cable which is color coded.
Wire color
Description
White
Modbus over RS485-A
Green
Earth
Brown
Modbus over RS485-B
Red
8-16v dc power input
Black
Power Ground
Battery Connections
The ModbusLink-M/S has an internal battery to power the unit; however, external power (8-16v dc) can be
applied to J3. If external power is applied, the internal battery is automatically cut off and the module runs
off the external supply. The performance/functionality of the module is identical, regardless of the power
input source. If the external supply is removed, the unit automatically shifts to battery power. This transition
is transparent and does not interrupt the normal operation of the module.

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4. Setup and Operation
Modbus Connections
The ModbusLink-M would be connected to a Modbus Data Master/Logger via either the RS232 or the
RS485 port. There is no need for further battery connections.
From the Modbus sensor’s perspective, the ModbusLink-S replaces the Modbus Master on the remote end of
the connection. The Modbus sensors would connect to the ModbusLink-S just as they would to a Modbus
Master/Logger/ data recorder.
The unit supports Modbus (RTU mode) over RS232 or RS485. A simple command can be used to switch
between RS232 and RS485 modes. The ModbusLink-M module is shipped with a NULL modem so that it
can communicate with a Modbus Master or PLC (RS232 mode only). The ModbusLink-S modules can
interface with a modbus sensor using either the RS232 or RS485 port. No NULL modem is required for
RS232 mode.
ModbusLink Network basics
A ModbusLink network consists of ONLY one master (ModbusLink-M) and one or more slave
(ModbusLink-S) modules with the same Network-ID. All slave units must have the same Network-ID as
the Master in order to be able to be part of the same network. For the purpose of simplicity, the Network-ID
can be represented by an imaginary physical wire connecting each ModbusLink module to other
ModbusLink modules (within radio range) having an identical Network-ID, in a mesh-like topology.
Multiple networks each with their own Master and Slave(s) can coexist within range of each other, provided
they have unique Network-IDS. The default Network-ID for all modules (ModbusLink-M and
ModbusLink-S) is ‘15’. No two ModbusLink-M modules with the same Network-ID should be within range
of each other.
When the Modbus Logger sends a Modbus command to the ModbusLink-M module, it extracts the address
information from the command and tries to find a ModbusLink-S module with the same address in the
network. If the destination node is not within radio range of the ModbusLink-M module, it will try to
discover a route via intermediate ModbusLink-S modules. If multiple routes are possible to the destination,
the most efficient route will be selected.
In the above figure, consider the example where the ModbusLink-M module receives a Modbus command
from the Modbus logger addressed to Modbus Sensor #6.The ModbusLink-M broadcasts a route discovery
request to all ModbusLink-S modules in the network. Nodes#2, 3, and 5 receive the discovery request. They
each note that they have a path to M.

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Node# 3, 5 rebroadcast the discovery request. The request is received by Nodes 2, 4 and 6. Node 6 notes it
has a path to M through 2 and sends the route complete message to M through 2. Node 4 also rebroadcasts
the discovery request which is also received by 6; however, it is ignored by 6 since it already has a superior
route.
Once a route has been established, data can be sent through the route to the destination node. Data messages
are never broadcast to conserve power. They are only addressed to a single node (unicast) which could either
be the destination for the message or an intermediate node en-route to the destination as shown below:
The master will send all data destined for node 6, to node 2. node 2 will in turn forward the message to node
6. The other nodes do not play any role in delivering the message to node 6, thus conserving power.
If an intermediate node cannot deliver a message to the next hop, it informs the sender, which starts a new
route discovery.

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Setup
Each ModbusLink-S module in the network must have a unique node address. The address of the
ModbusLink-S module must match that of the modbus Sensor connected to it. The ModbusLink-S can be
configured to operate in Auto address mode or it can also be assigned a static address. The ModbusLink-M
module does not need any address configuration.
The ModbusLink module is shipped with an internal D-Cell battery that is used to power the radio and
communications with a local modbus sensor (if connected). To prevent damage, the internal battery is
disconnected before shipping. Unscrew the lid and connect the battery connector to J5 as shown in the figure
below. If, using automatic Node address configuration(described below), ensure that the Modbus sensor is
connected to the ModbusLink-S at power up . Also ensure that the modbus communication parameters like
baud, parity etc of the sensor are the same as ModbusLink-S module. If the parameters are different from the
default settings of the ModbusLink-S, refer to the Appendix for details on how to change the Modbus
communication parameters.
If configured to operate in the automatic address mode, The ModbusLink-S modules will automatically scan
the RS232/RS485(based on configured port) ports for a Modbus sensor, during the power up sequence. On
receiving a response from the sensor, the ModbusLink-S Node sets it own address to that of Modbus sensor
(If no sensor is found, the ModbusLink-S will retry after an hour. If the automatic configuration is not
desired, the ModbusLink-S node can be assigned a static address. The static address assigned to each node
must be unique throughout the network and match the address of the local modbus sensor connected to it