Users’ Manual
ESM-40S High sensitivity settlement monitoring system
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8 CONNECTING EPS-40S TO MODBUS DATALOGGER
8.1 Introduction
Encardio-rite model ESM-40S settlement monitoring system use the industry standard Modbus Remote
Terminal Unit (RTU) protocol to communicate with dataloggers. As the name suggests, Modbus was
designed to work on what is known as a bus network, meaning that every device receives every message
which passes across the network.
Model ESM-40S sensors use the RS-485 electrical interface to communicate over long distance cables up
to 1.2 km. Any suitable Modbus datalogger with either GSM/GPRS or RF transmission facility can be
connected for datalogging and wireless data transmission.
Encardio-rite model ESDL-30 datalogger can also be used with an additional Modbus card, if specifically
ordered. However, maximum limit of Modbus seepage sensors that can be connected to this ESDL-30
datalogger version is seven.
8.2 Connection details for ESDL-30 datalogger
ESDL-30 datalogger has a Modbus (RS-485) port also besides the three SDI-12 ports (channels). Sensors
with Modbus (RS-485) output can be connected to the datalogger as shown in figure below. Battery should
be placed in the datalogger after the connections have been successfully done.
8.3 Wiring details for any other Modbus datalogger
Figure 8-2 Wiring details to connect ESM-40S sensor with Modbus output to suitable datalogger
Modbus
interface
Modbus Sensor
Addr: 0x01
Red: +12 V
Black: GND
Green: D+
White: D-
Modbus Sensor
Addr: 0x02
Modbus Sensor
Addr: 0x03
Bus cable
Figure 8-1 Connection of Modbus (RS-485) 4-core cable bus (from settlement sensor
chain) to ESDL-30 datalogger
