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16. SERIAL COMMUNICATION OPTIONS
A serial communications board may be connected to the DPM-3 meter main board at plug
position P13 (middle position). Available boards are RS232, RS485 (with dual RJ11 connec-
tors), RS485 Modbus (with dual RJ45 connectors), USB, and a USB-to-RS485 converter. The
dual connectors of RS485 boards are wired in parallel to allow daisy chaining of addressable
meters without the use of a hub. Three serial communication protocols are selectable for all
serial boards: Custom ASCII, Modbus RTU, and Modbus ASCII.
A USB-to-RS485 converter board allows a DPM-3 meter to be interfaced to a computer and
to be the device server for a network of up to 31 other meters on an RS485 bus, while itself
retaining all capabilities of a meter. The remote meters need to be equipped with our RS485
digital interface board DPM-3-OPT-TRS485. This board has dual 6-pin RJ11 jacks, which are
wired in parallel to allow multiple meters to be daisy-chained using readily-available 6-wire
data cables with no need for hand-wiring or an RS485 hub. The outer two wires are used for
ground.
Use 6-wire, straight-through data cables, not 4-wire telephone cables or crossover cables,
all the way from the device server to the last device on the RS485 bus. Connect ATX to ATX,
BTX to BTX, etc., with no crossover as you go from device to device.
To connect a meter with a USB board to a computer, use a USB cable with Type A and
Type B connectors. The computer will display “Found new Hardware” followed by “Welcome to
the Found new Hardware Wizard.” Follow the instructions for software installation from a CD.
When the installation is complete, use Device Manager to determine the COM port. To get to
Device Manger, go to the Windows Control Panel, click on System, click on the Hardware tab,
then click on Device Manager. Go down the device list and click on Ports (COM & LPT) and
USB serial port (COM #). Note the COM port # for use with communications to your meter,
then exit Control Panel. If you later need to change the COM port, right-click on USB serial port
(COM #), then on Properties, Port settings, and Advanced. Change port to the desired number,
click OK, then exit Control Panel.
DOWNLOADABLE SOFTWARE AND MANUALS
Windows-based software is available from Transducer Techniques to program our meters
and transmitters via a PC using the serial interface. This software can be downloaded at no
charge from www.transducertechniques.com/online-manuals.aspx. Please see Section 19 for
details.
Software manuals for the Custom ASCII and Modbus Protocols can also be downloaded from
www.transducertechniques.com/online-manuals.aspx.
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