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Multiple Omega 77000 (RS232) Problem

I am using 2 omega 77000 controllers. I need to acquire data from both simultaneously with a LabVIEW program.

#1
I am able to control only one of them
COM address is correct, but I donot know about hardware address (LabVIEW program works fine)

#2
It is not allowing me to change ID number . If both are same will it be a problem.

#3
At one point I was able to communicate with both simultaneously, then again it is not communicating.


We plan to use 10 of them in simultaneously. If even two is a problem, it is a serious issue.
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Message 1 of 3
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Hi Sandeep,
I don't know your controller, but I know it won't work, if you use the
old serial vis, because they do not handle the serial buffer correctly
and you have dataloss.
I always use VISA Configure Serial Port, VISA Set I/O Buffer Size with
write and read buffer set to 8kB.
To discover behaveure of connected, unknown serial instruments, ist
helpful to DISABLE termination character at VISA Configure Serial Port
and display the states of important serial lines, like CTS, DCD, DSR,
DTR, RI and RTS. For this insert a proprty Node in the wired VISA
resource name. You find the property node in Functions/Instrument
I-O/VISA/VISA advanced in the diagram context menu.

If you open all required COM ports in this manner, LabVIEW and the
operating system will put
all received data in the 8k- buffers of each
port (until buffer- overrun occurs).
All you have to if all ports are opened, is to cyclicly check all
buffers contents using a property node like above with the property
"Bytes at Port" and read out data with VISA read.
Prevent buffer overruns!! For instance, if you use 115200 Bd and you
want to have double security, buffers have to be emptied, when they are
filled with 4kB max. With 8N1, 1Byte uses 10 Bits in transmission, so
there will be 11520 Byte transmitted per second at max. So you better
have all buffers emptied after 356 ms.

I hope this helps,
Rainer

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Message 2 of 3
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Hi,

"Sandeep" wrote in message news:5065000000080000002FCC0000-1079395200000@exchange.ni.com...
> I am using 2 omega 77000 controllers. I need to acquire data from both
> simultaneously with a LabVIEW program.
>
What you need is the RS-485 model. You then connect all 10 controllers to a single
COM port (you will need a converter at the PC side).
That way, you can use the address to communicate with each specific controller.

regards, Matt
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