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A challenge is that Laureate meters use RJ11 jacks, while Laureate LT series transmitters use screw-clamp connectors for three discrete wires. Laureate meter and LT series transmitters support the Modbus RTU protocol and Laurel’s simpler ASCII character based Custom ASCII protocol. If multiple analog input meters or transmitters are digitally addressed in command mode on an RS485 line using the Modbus RTU protocol or the Custom ASCII protocol, the rate becomes about 2 readings per second. Both boards support the Modbus protocol and Laurel’s Custom ASCII protocol, as well as half-duplex or full-duplex RS485 communications. Set the PC to N81 for the Custom ASCII protocol, or to N82 or E81 for the Modbus RTU protocol. A single analog input meter or transmitter can stream readings to a PC at up to 60 readings per second and the Custom ASCII protocol set to continuous (or streaming) model. RS232 (serial) data feed from the ARES 21. Custom cable available upon request. The older RS232 standard uses single-ended signals, is more sensitive to noise, and is only rated for distances up to 50 ft (15 meters). The board with dual RJ11 jacks is the more popular since is can use commercial straight-through, non-reversing, 6-wire data cables with RJ11 connectors.

Not more than one breakout board is required per RS485 line. What cable should I use to connect meters with an RS485 port to the USB port of a PC? If the PC is connected to the multiple Laureate instruments on an RS485 bus via an Ethernet-to-RS-485 gateway board or a USB-to-RS485 gateway board, use Laurel’s free XLOG2 datalogging software. The presence of a new board and the type of board are automatically sensed by the meter’s firmware or by Instrument Setup (IS) software. Both protocols (or communication languages) are built into the instrument’s firmware and are user selectable. What communication protocols are supported by RS485? Can I mix Laureate LT transmitters and meters on the same RS485 line? Laureate meters are modular with a middle slot reserved for a communication board, as illustrated in our Laureates Overview web page. A meter will a thermocouple input and set for Modbus RTU needs to set to full duplex even if the wiring and the receiving unit are for half duplex.

Half duplex has the advantage of only using three wires: ARX/ATX, BRX/BTX and GND. This allows RS-485 to implement linear bus topologies using only two wires. The MEV RS485 Repeater allows communication between RS485 systems in otherwise impossible situations. This provides high noise immunity and allows distances up to 4,000 ft (1200 meters). QUICK TIP-If you are encountering noise or irregular or abnormal problems with a Modbus serial link, the problem is likely related to grounding, incorrect shielding, or wiring power wires next to Modbus wiring. If you want to change something in your bus, e.g. add new Bricks or Bricklets, you have to power down the stack you would like to change, change it and repower it. If you want to use a stack with RS485 Extension in your existing Modbus network, you have to match the values with the other bus participants. Why have we used PACE in our 48V Batteries? These pins have to be connected to handshaking outputs at the PC side on the RS232 port. RS485 cable length can be as long as 1.2 km, while RS232 only about 25 meters.

Otherwise RS232 would be my next best option. Laureate RS485 boards are available in versions with dual RJ11 jacks (ordering option 2, board P/N L485) and with dual RJ485 jacks (ordering option 4, board P/N LMOD). These cables allow the dual RJ11 jacks of the RS485 option board of Laureate meters (digital interface ordering option 2) to be daisy chained and to be addressed digitally with no need for a hub. By using two jacks, up to 31 L485 boards can be connected in parallel for daisy chaining using readily available CBL03 data cables with no need for a hub. Boards can be ordered installed with a new meter, and they can also be purchased separately later and be simply plugged in. On the Raspberry Pi, we also installed a 1-Wire Pi Plus board, and this is used with a temperature sensor fitted in the shed to monitor the air temperature, which is also posted to the MQTT server and Home Assistant. The solution is provided by the Laureate DIN rail mounted breakout board, which provides two RJ11 jacks with six screw clamp terminals all wired in parallel.