Unipi Extension xG18 is an extension module for connecting up to eight Unipi 1-Wire temperature sensors (RJ45 connector). For communication with the control system, the module uses the RS485 serial interface and the Modbus RTU protocol.
Unipi Extension xG18 is a cheap and reliable tool for connecting and reading temperature from up to eight Unipi 1-Wire temperature sensors (RJ45 connector). The module uses the RS485 serial line and the Modbus RTU protocol for communication with a control system. Although primarily designed to be used with Unipi controllers, the xG18 can be implemented into any system featuring the RS485 interface and Modbus RTU support.
Unipi Extension xG18 is suitable for:
Sensors connected to the module use the 1-Wire bus. In contrast to a standard 1-Wire bus, only one sensor can be connected to each xG18's channel - this arrangement improves the reliability of temperature measurements and prevents the failure of the entire bus in case a single sensor fails.
Communication between the module and the control system is done through the RS485 serial line using Modbus RTU protocol. Communication parameters can be configured either on the hardware side via DIP switches, or on the software side through Modbus registers. Hardware configuration is sufficient for most applications, while the software configuration offers broader options, namely a broader range of addresses and bitrates.
The xG18 can be used with any device featuring the RS485 interface and software supporting Modbus RTU communication.
The module has full software support in Mervis IDE 2.3.0 or newer. A tutorial for connecting the xG18 to Mervis IDE is available on this link.
The xG18 features a durable aluminum chassis with IP20 protection and is designed for installation onto a standard DIN rail (rail holder and mounting screw are included in the package). A set of LED indicators serves for indicating power, 1-Wire channel status, and RS485 communication.
The technical specification can be found under the Parameters tab (see above), or in the product's documentation (see the Files tab above).
Modbus register map
Table overview of Modbus registers
Declaration of conformity
User manual and technical documentation
Product features and technical information
|Sensors per channel||1|
|RS485 interface||1× (Modbus RTU)|
|RS485 galvanic isolation||No|
|Indicators||LED indication of channel states, power and RS485 communication|
|Power||5–24 V⎓ (protection against overvoltage and pole reversal)|
|Dimensions||72 × 91 × 22 mm (w, h, d)|
|Installation||DIN rail (35 mm)|