RS485 RJ11 Interface Board P/N L485 for Laurel Electronics 1/8 DIN Instruments

The Laureate interface board P/N L485 with dual RJ11 jacks allows multiple Laureate meters, counters, timers and remote displays to be connected to the same RS485 line. The two RJ11 jacks (or connectors), are wired in parallel. One of the jacks can be connected to the USB port of a PC by using our RS485-to-USB converter cable (P/N CBL06) for data I/O or for programming by a PC running our Instrument Setup (IS) software. Having two RJ11 jacks wired in parallel allows multiple instruments to be daisy-chained using readily available 6-wire data cables or patch cords with RJ11 plugs (P/N CBL03). In the absence of a computer, a single Laureate meter with an L485 RS485 board can drive multiple Laureate 6-digit remote displays.

Ideal complements to the P/N L485 RS485 interface board are Laurel's Ethernet-to-RS485 gateway board, which connects a meter network to an Ethernet LAN, and the USB-to-RS485 gateway board, which connects a meter network to a host PC via a standard USB cable. Both gateway boards provide an RJ11 interface to an RS485 network, which can consist of multiple Laureate meters that are easily daisy-chained via CBL03 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 4,000 ft (1200 meters) 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. The meter, counter or timer should be programmed for full duplex operation, even if the RS485 board is jumpered for half duplex.

Two serial protocols are user-selectable for RS485: Modbus RTU and Custom ASCII. For detailed information on our protocols, please see our communication user manuals.

• The Modbus RTU protocol is an international standard and allows Laureates to share the same RS485 data line 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. Modbus RTU works in a master-slave (or query-response) mode, and its use requires an external Modbus master, which is typically a PC. Meters with a thermocouple input and using the Modbus RTU protocol should be set to full duplex.
• Laurel's Custom ASCII protocol is the simpler of the two protocols and uses ASCII strings. It is recommended if the only devices on the RS485 data line are Laureate meters. It supports up to 31 digital addresses. It can be set to a command mode under control of an external master, or to a continuous streaming mode where data is output at specified intervals at rates up to 60 per second.

The Laureate LMOD RS485 interface board is similar to L485 interface board, except that it providess dual RJ45 connectors instead of RJ11 connectors. That board is not supported by readily available cables CBL03 and CBL06 data cables. Therefore, use the L485 board with dual RJ11 connectors as described in this web page, unless design specifications call our RJ45 connectors.

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 CBL03 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 gateway board, 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.