RS485 Interface Board for Laurel Electronics 1/8 DIN Instruments

The Laureate RS485 interface board allows multiple Laureate meters, counters, timers and remote displays to be connected to the same RS485 line. Dual RJ11 jacks allow multiple devices to be daisy-chained using readily available 6-wire data cables or patch cords with RJ11 plugs. Also, in the absence of a computer, a single Laureate meter with an RS485 board can drive multiple Laureate 6-digit remote displays.

Ideal complements to the RS485 interface board are Laurel's Ethernet-to-RS485 converter board, which connects a meter network to an Ethernet LAN, and the USB-to-RS485 converter board, which connects a meter network to a host PC via a standard USB cable. Both converter boards provide an RJ11 interface to an RS485 network, which can consist of multiple Laureate meters that are easily daisy-chained via readily available 6-wire data cables.

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

Three serial protocols are user-selectable: Modbus RTU, Modbus ASCII, and Laurel ASCII. For more information, please see our Modbus Protocol Serial Communications Manual and our Serial Communications Manual.

• 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.

The Laureate RS485 Modus interface board is similar to the RS485 interface board, except that it features dual RJ45 connectors instead of RJ11 connectors. While use of RJ45 connectors is recommended in the Modbus standard, RJ11 connectors are also popular, and both of our RS485 boards support the Modbus communications equally.

The Laureate RS485 interface board provides two 6-pin RJ11 jacks, whose pins are wired in parallel. This allows multiple Laureates to be daisy-chained using readily available 6-wire data cables with no need for an RS485 hub. The resulting RS485 network can be connected to a LAN via Laurel's Ethernet-to-RS485 converters, or to a host PC via Laurel's USB-to-RS458 converter.

The signal levels of the Laureate RS485 board are compliant with the EIA/TIA-485 standard. Devices by different manufacturers can share the same RS485 data line, provided that their connectors are wired appropriately.