How to connect voltage monitoring meter with RS485 out, to a computer with Modbus RTU? Should I use a converter to RS232 and connect to serial COM port of computer? Should I use RS485 to USB converter to connect? Can I connect directly to serial COM port from A,B and Ground of RS485 using D9 connector pin? Then A,B and Ground to which pins of D9 in Modbus RTU? ND20 pinout RS485 Details
Yes, you should use a RS485 to USB converter to connect the ND20 with your computer.
At minimum you need to connect the A (sometimes called "-") and the B (or "+") line of your ND20 to the same lines of your RS485/USB adapter. Check your RS485/USB adapter manual for the pinout. Remember, the "A" line can alternatively be called "-", and "B" might be called "+". See here for more RS485 application info.
Connecting GND is recommended, though in most situations it should work without.
You need to know the baud rate / bits per second (9600? 19200?) the ND20 uses. You need to set this in the PC application.
After having everything connected and ready to operate, you need use a PC application that accesses the RS485 converter ("COM" device on Window, e.g. "COM6"). The PC application needs to request measurement values and receive the results according to MODBUS RTU protocol specification. Our free Docklight evaluation can help with MODBUS, but the most convenient solution is a small MODBUS master tool like this new freeware called QModMaster.
