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Laureate USB to RS485 Gateway Board Frequently Asked Technical Questions
This gateway board allows a 1/8 DIN Laureate meter or counter to be connected to the USB port of a PC and also to an RS485 bus with a mix of up to 31 Laureate instruments. This allows a single USB port of a PC to read data from to 32 Laureate instruments, including the host meter or counter, or to set up these instruments on the fly in command mode. The instruments on the RS485 bus can be Laureate transmitters as well as 1/8 DIN meters or counters.
This gateway board can be installed as an option in the middle slot of a Laureate meter or counter, which will continue to operate in its normal mode. The board can be ordered with a new meter or counter by selecting option 6 under Data Interface, or it can be ordered separately as P/N LUSB485 and be plugged into the middle backplane slot. Its presence is automatically sensed by the meter’s computer board, which enables USB communications and brings up the appropriate setup menu items.
Laureate meters, counters and transmitters support two protocols, both of which offer a command mode which allows multiple instruments to be digitally addressed. The protocols are Laurel’s Custom ASCII protocol, Modbus RTU protocol for analog input DPMs, and Modbus RTU protocol for pulse input counters. Laurel’s Instrument Setup (IS) software and XLOG Datalogging software do require use of these protocols.
To connect the USB port of the PC to the gateway board in the host meter, use a common USB cable with a square USB Type A connector on the meter end and a flat USB type B connector on the PC end. Laurel sells a 1.8 meter (6 foot) version of this cable as CBL05. To connect the gateway board to the first meter on the RS485 bus and then to daisy chain the remote meters, use Laurel’s data cables CBL03, which are available in 30 cm (1 ft) and 2 meter (7 ft) versions. The CBL03 cables have an RJ11 connector on each end and are non-reversing, as described in our cables web page. They plug into the dual RH11 sockets of each meter with an RS485 communications board P/N L485.
Laureate transmitters use the same software as meters and counters, but they do not have RJ11 sockets, only screw terminal connectors. To add transmitters to an RS485 bus designed for CBL03 data cables, use one Laurel breakout board in the bus. That board makes a parallel connection between two RJ11 sockets and three active screw terminals so that Laureate meters and transmitters can be used on the same bus.
The Laureate host meter and the remote meters on the RS485 bus can be individually programmed from their front panel, including the choice of protocol and digital address. The meters are also automatically discovered by Laurel’s Instrument Setup (IS) software, which allows setup parameters to be changed remotely by the computer.
Data from all meters can be logged using Laurel’s free XLOG2 datalogging software, which is described in our web page at https://www.laurels.com/datalogging-software.php and user manual at https://www.laurels.com/downloadfiles/datalogging-manual.pdf.
Readings over the RS485 bus are limited to about 2 readings/second at 9600 baud.
The USB cable should be limited to 5 meters (16 ft) according to the USB 2.0 specification. The length of the RS485 able can be up to 1200 meters (4000 ft).
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