Serial Communication Options for Laurel Electronics 1/8 DIN Instruments

A serial communication option board allows a Laureate digital panel meter, counter or timer to be interfaced to a PC for programming via Laurel's Windows-based Instrument Setup Software, or to output readings to a remote PC, PLC or other device with a serial communication port. The transmitted data may include the latest reading, peak value, valley value, alarm status, and setup information. The data can then be displayed, processed and data logged. The data can also be received by a Laureate 6-digit remote display, which will display the serial data and also process the serial data to control relay outputs and generate a scaled, isolated 4-20 mA, 0-10V or -10V to +10V analog output.

If the primary objective is to program a meter directly from a PC using Instrument Setup Software, an RS232 interface board or a USB interface board is recommended, depending on the available PC port. Once the meter has been programmed, either board can be removed if no longer required.

If the objective is to connect a network of meters to a PC, our USB 2.0-to-RS485 converter board can be used. That board can be connected to a PC via a USB port, and also act as the server for up to 31 meters on an RS485 bus via an RJ11 connector. The remote meters must be equipped with Laurel's RS485 interface board. That board features dual RJ11 connectors for RS485 daisy-chaining using commercial 6-wire RJ11 data cables, with no need for a hub.

If the objective is to connect meters to an existing Modbus RS485 bus, either of two RS485 interface board can be selected. Our RS485 Modbus interface board uses RJ45 connectors as recommended by the Modbus standard, while our RS485 interface board uses RJ11 connectors, which are also used for Modbus. Both boards are fully compatible with the Modbus RTU and Modbus ASCII protocols, as are all Laureate serial interface boards. Both boards provide dual connectors (RJ485 or RJ11) for RS485 daisy-chaining using commercial 6-wire data cables with the appropriate connector (RJ485 or RJ11), with no need for a hub.

If the objective is to connect a meter to an Ethernet LAN, our Ethernet interface board allows a meter to be connected to an available router port using a standard Ethernet cable. Our Node Manager software makes node discovery and setup exceptionally simple.

If the objective is to connect a network of meters to an Ethernet LAN, our new Ethernet-to-RS485 converter board should be selected. That board can be connected to an Ethernet LAN utilizing a single router port and also act as the server for up to 31 meters on an RS485 bus via an RJ11 connector. The remote meters must be equipped with Laurel's RS485 interface board. That board features dual RJ11 connectors for RS485 daisy-chaining using commercial 6-wire RJ11 data cables, with no need for a hub. Our new Node Manager software makes meter discovery and setup exceptionally simple.

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 per line would require a repeater for impedance reasons.
• The Laurel ASCII protocol is recommended if the only devices on the RS485 data line are Laureate meters. It supports up to 31 digital addresses.