High-Speed Ethernet to RS485 Gateway Board, P/N LNET1485

LNET1485 is a second generation communications board that plugs into the middle slot of a Laureate host 1/8 DIN digital panel meter, counter or timer. It provides high-speed Ethernet and RS485 ports to connect the host instrument to an external local area network (LAN) while also serving as an Ethernet-to-RS485 gateway to an RS485 bus with with up to 31 Laureate meters or LT series transmitters. High data rates are a major advantage compared to Laurel's first-generation communication boards, which include the legacy LNET485 board.

Ethernet operation complies with IEEE 802.3 and utilizes an industry-standard RJ45 jack for a 10/100 Base-T connection to a local area network (LAN) or directly to a PC or HMI. Multiple instruments, each with their own assigned IP address, can be individually addressed using the Modbus TCP protocol. Internet WAN connectivity is supported so that instruments can be set up and read over the Internet. Data rates can be 10 or 100 Mbits/sec depending on the router. Using Ethernet, cache of the LNET1485 board can be polled via Modbus TCP every 2 msec.

An RJ11 connector is standard for RS485 and can be used for meter programming, for data polling as a Modbus slave at up to 115200 baud, or for operation as a Modbus master at 19200 baud to an RS485 bus with up to 31 adressable Laureate meters or LT series transmitters. Meters on the RS485 bus can be daisy chained using our CBL03 data cables. LT transmitters can be added using our BKBD breakout board.

Use of cache memory is a key feature of the LNET1485 board. It allows the host meter to be polled at the maximum rate allowed by the meter's main board, and in turn to be polled asynchronously at a much faster rate using external Ethernet or RS485 communications with Modbus RTU/TCP commands. These are documented in our user manual for Gen 2 Laureate communication boards. Updated analog readings can be retrieved every 17 or 20 msec, depending on the meter's 60 Hz or 50 Hz AC line noise rejection setting. Cashed counter readings can be retrieved every 10 msec.

Setup of Ethernet and RS485 communications uses our free Laurel Network Setup (LNS) utility running on a PC. That software automatically discovers the board's IP address assigned by the network router, the COM port used for RS485 communications, the meter type, and the signal conditioner type. Our CBL06 RS485-to-USB adapter cable and CBL08 RS485 splitter cable are required to connect the board's RJ11 port simultaneously to the USB port of a PC an to the external RS485 bus. The board's RS485 port can then be used to be used to set up the host instrument and instruments on the RS485 bus using our free Instrument Setup (IS) software in lieu of front panel programming.