RS485 Modbus Interface Board for Laurel Electronics 1/8 DIN Instruments

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RS485 Modbus interface board

Key Features
  • Allows up to 247 meters to be addressed using the Modbus protocol.
  • Allows up to 31 meters to be addressed using the Laurel ASCII protocol.
  • Dual RJ45 connectors allow daisy chaining of meters without a hub.
  • Suitable for all 1/8 DIN Laureate DPMs, counters, timers & remote displays.
  • Jumper selectable 2-wire (half duplex) or 4-wire (full duplex) operation.
  • Selectable baud rates to 19,200.
  • Isolated from meter and power grounds.

The Laureate RS485 Modbus interface board allows multiple Laureate meters, counters, timers and remote displays to be connected to the same Modbus RS485 line. Dual RJ45 jacks allow multiple devices to be daisy-chained using 8-wire data cables or patch cords with RJ45 plugs.

The RS485 Modbus interface board is identical to the RS485 Interface Board, except that it uses 8-wire RJ45 jacks as recommended by the Modbus standard, as opposed to 6-wire RJ11 jacks. Both boards are equally compatible with the Modbus RTU and Modbus ASCII protocols.

Operation can be configured for full-duplex or half-duplex operation using jumpers on the RS485 Modbus board. Transmission distances up to one mile are possible. In case of long line lengths, a jumper can be plugged in the RS485 Modbus board at the end of the line to insert a 120-ohm termination resistor to minimize signal reflections.

Two serial multipoint protocols are user-selectable and are implemented on the meter main board: the Laurel ASCII protocol and the Modbus protocol. For detailed information, please see our Modbus Protocol Serial Communications Manual and Serial Communications Manual or

  • The Modbus protocol is an international standard and allows Laureates to share the same RS485 data lines with non-Laurel devices. It supports up to 247 digital addresses. Use of more than 31 Laurel RS485 Modbus boards requires repeaters for impedance reasons.
  • The Laurel ASCII protocol is the simplest and is recommended if the only devices on the RS485 data line are Laureate meters. It supports up to 31 digital addresses.
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