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

RS485 meter interface board

Key Features

  • Includes dual RJ11 connectors for daisy chaining of meters without a hub.
  • Allows up to 247 meters to be addressed using the Modbus RTU protocol.
  • Allows up to 31 meters to be addressed using Laurel's Custom ASCII protocol.
  • Supports continuous data streaming with Custom ASCII protocol.
  • Selectable full-duplex or half-duplex operation.
  • Suitable for all 1/8 DIN Laureate DPMs, counters, timers & remote displays.
  • Selectable baud rates to 19,200/sec.
  • Isolated from meter and power grounds.
  • Ideal for use with Laurel's LUSB485, LNET485, LNET1485, LWIFI485, LWFIX485 gateway boards.

The Laureate interface board P/N L485 with dual RJ11 jacks allows multiple Laureate meters, counters, timers and remote displays to be daisy-chained to the same RS485 line and to be addressed in command mode. 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 and for programming by a PC running our Instrument Setup (IS) software. Daisy-chaining uses our readily available 6-wire data cables (or patch cords) P/N CBL03 with RJ11 plugs. In the absence of a computer, a single Laureate meter with an L485 RS485 board can drive multiple Laureate 6-digit remote displays.

Signal levels of the L485 board are compliant with the EIA/TIA-485 standard. This allows devices by different manufacturers to share the same RS485 data line, provided that their connectors are wired appropriately.

Up to 31 Laureate instruments with an L485 interface board can be daisy-chained with our cables P/N CBL03 and be addresed in command mode by a Laureate RS485 gateway board where one of the ports is RS485 with RJ11 connector and the other port is different for connection to a PC or HMI. The different ports can be the following for these different gateway boards: USB for LUSB485, Ethernet for LNET485, high speed Ethernet for LNET1485, USB or WiFi with an internal antenna for LWIFI485, USB or WiFi with an external antenna for LWIFIX485.

RS485 RJ11 connector wiring

Full-duplex or half-duplex operation can set by jumpers; however, the host instrument should be programmed for full duplex even if the board has beenjumpered for half duplex. Transmission distances up to 4,000 ft (1200 meters) are possible. To avoid signal reflections with long lines, a 120-ohm termination resistor ca be jumper selected.

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.
  • 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 Laureates. 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. It is not recommended for new designs, since the L485 board provides more supporting cables and hence is easier to use.

Operation with a Gateway Board
Laurel RS485 network connected to PC or Internet via an RS485 gateway board

Electrical Specifications

RS485 RJ11 Board Specifications
Laurel Part Number L485
Connection Full duplex (ATX, ARX, BTX, BRX) or
half duplex (ATX / ARX, BTX / BRX)
Data rates 300, 600, 1200, 2400, 4800, 9600 baud
No. of devices on data line Up to 31 without a repeater, 247 Modbus addresses
Connectors Dual RJ11 jacks for daisy chaining without a hub
Line length, max Up to 5000 feet (1500 meters) at 9600 baud depending on cable
Isolation 250V rms working, 2.3 kV rms per 1 min test
ESD Protection 15 kV per IEC 1000-4-2
EMI Immunity 10 V/m per IEC 1000-4-3
EFT Protection 2 kV per IEC 1000-4-4s
Short Circuit Protection Continuous
Cable to PC USB port RS485-to-USB adapter cable P/N CBL06
Cable for daisy chaining Data cable P/N CBL03
Selectable Protocols Modbus RTU, Custom Laurel ASCII

Protocol Specifications (protocols reside on Main Board)

Modbus RTU Protocol
Standards Compliance Modbus over Serial Line Specification V1.0 (2002)
Protocol Type Master-slave, query-response command mode
Data Streaming Mode Not supported by Modbus specification
Data Formats (selectable) 1. No parity, 8 data bits, 2 stop bits
2. Odd parity, 8 data bits, 1 stop bit
3. Even parity, 8 data bits, 1 stop bit
Main Board Revision Level Level 5 or above
Custom ASCII Protocol
Standards Compliance Laurel proprietary protocol
Data Format No parity, 8 data bits, 1 stop bit
Protocol Type Text string based command mode or continuous data streaming mode
Data Streaming Mode User selectable for up to 60 readings/sec
Main Board Revision Level Any
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