Instrument Control (GPIB, Serial, VISA, IVI)

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problem with modbus server I/O

hello,

 

I'd like to develope an application to acquire  data from a load cell via modbus serial. I'm using labview 9.0 and is the first time i work with this program so i appologize if my questions aren't very accurated.

 

 

For this application i created a modbus I/O server from where create shared vars in order to ve able to read the data i was interested in. I followed the steps shown in this tutorial ---> http://www.ni.com/swf/demos/us/labview/dscmodbus --- but instead of usin the "ModbusEthernet" option i left the "Modbus serial" one. Then i setted up the modbus comunication :port COM!, baud rate:38400,etc. and when i executed the program in continuously everything worked fine. the problem came when i changed the load cell (just this item since the RS-485 modbus conversor and the strain gauge cell remained the same. After changing the load cell i executed the program again and didn't read anything...

 

The arrows next to the variables that show the working state of those show up in green during the first time i execute the program (although no value apears in the var field) but once i stop the execution and i start the program again those arrows change into red color, and " bad quality for: \\my computer\modbus\400062" tag appears, beeing 40062 the register i want to read (which i was able to read before).

 

The only way i found out to make this "bad quality" error disappear is changing the var'sproperties and deactivating the "enable aliasing" option, but still there is no value reading...

 

After that I tried wit Ni modbus library but didn't work too, appearing the 6010 error code after 5 seconds of execution (i figure out that there's no response and the program sends a time out error).

 

I'm really stuke and i will appreciate any help

 

thanks

 

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