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Modbus DYACON UA-1 Manual
5.0 Modbus
5.1 Modbus Summary
Modbus is a simple protocol that can be transmitted over several modes including TCP/IP, TIA-
232-A (RS-232), TIA-485-A (RS-485), TCP/IP, SMS, and many others.
DYACON UA-1 uses Modbus-RTU over RS-485.
UA-1 is a slave device and must be connected to a host device, such as a programmable logic
controller (PLC), host computer with an RS-485 adapter and Modbus software, or to the
DYACON weather station control module.
RS-485 is a robust, differential pair electrical protocol that is noise immune and capable of long
cable runs. With twisted pair cabling, such as CAT-5, distances over 1200 m (4,000 ft) can be
achieved. UA-1 can be configured for 1200 bps or 2400 bps to extend the range. Relatively long
runs are achievable even without twisted pair cables.
The wide operating voltage range and low power of UA-1 allows for power to be injected over
the same data cable without concern for excess voltage drop. (Two wires for power and two for
data.)
For example, 1200 m (4000 ft) of Cat-5 cable (24 AWG) will result in a voltage drop of less
than 0.2 V at an operating current of 2 mA.
UA-1 ships standard with 20 ft (5 m) of non-paired, outdoor-rated cable.
5.2 Modbus Utilities
The address of the sensor and other parameters are configurable. A Modbus computer utility
may be required to change these settings. A number of utilities are available including:
ModBus Constructor www.kurysoft.com
Simply Modbus www.simplymodbus.ca
ModbusTools www.modbustools.com
Only ModBusConstructor and the companion ModbusReader have been tested with the Dyacon
product. Contact
support@dyacon.com for copies of the constructor files.
A list of Modbus software can be found at: www.modbus.org/tech.php
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