modbus RTU protocol datatypes

[seen]

Hai, Ravens

Your suggestions helped me a lot.Thank you verry much

I modified the VI and it is working fine. I am attaching the vi with this.

Changes :

RS-232 to USB converter removed.

MB serial init.vi is replaced with Serial Config VI.

Now i am going to connect 3 powermeters and log the data.

For my knowledge I would like to know which protocol will be better for connecting more instruments among  Modbus RTU/ Modbus ASCII/ Modbus TCP/ Ethernet.

Thanks,

[RavensFan]

I'm glad to hear it's working for you.

I would recommend Modbus RTU over Modbus ASCII.  It just seems to be more efficient.  In generally, Modbus ASCII requires twice the bytes to send data as opposed to RTU.  These basically are what you want if you are using a hardwired serial port configuration.

I would use Modbus TCP/IP if you are dealing with remote devices connected on a LAN.  The LAN infrastructure gives you an advantage over not having to run extra cables.  The disadvantage is that the communication stream could be affected by other network activity on the LAN.

[MogaRaghu]

Hello Subbulaxmi, Sorry to jump imto this thread. But I am also trying to readthe phase current with the LV MODBUS LLB.

But I do not the address map of  EM6400. Obviously I should contact Conzerv support - but the fact that i am asking here says so much of the support.

Kindly help me with the address map.

Thanks

Raghunathan

[shubhlaxmi22]

hello Raghunathan

                             what u exactly want regarding EM6400. i am attaching  png filefrom that u get an idea about modbus logic.First u need to check  ID of EM6400,parity should change to even.try this give me feed back

[MogaRaghu]

Hello Subbulaxmi,

Thanks for responding.

OK I could get the address map of the EM6400. The EM6400 was started in Simulation mode and I tried to query the address 3911. For this I used the VI that you had posted and it returned a 6002 error ( bad address ) and also tried some free software like ModScan32 from the net, with no luck.

Could you post the last VI that effectively communicated with the EM6400 ? I have LV 2009, LV 8.6, LV 8.0 and LV 7.1and can thus use any version. I am now starting to suspect the 485-232 convertor but before that I should have a cde that worked..

Been struggling for almost a day now and basic things like Com port settings, MODBUS protocol are almost by heart now 😉

[MogaRaghu]

Hello Shublaxmi,

After I posted my earlier reply there has been some progress with the Modscan32 ( demo) software. I'm able to read the EM6400 registers without problems. All because I dumped the 232-USB covertor and used a desktop that had a Serial Port. I still do not know why the laptop's have stopped using serial ports.

So this confirms that my PC com port + Cable + 232 to 485 convertor + EM6400 are all OK.

The issue now boils down to the "EnergyMeter.vi" that was posted in this thread. It keeps returning a TimeOut error. What could possibly be wrong ??

[parthabe]

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Raghunathan wrote:

Obviously I should contact Conzerv support - but the fact that i am asking here says so much of the support.

---

Hi Raghunathan, 

FYI, Conzerv has become Schneider Electric now.

I m an ex-employee of Conzerv. If you need further support reg the VIs, maybe you can mail me to vparthasarathi.1@tcs.com by keeping the subject line as something related to LV. I can ask my LV friends over there (they come rarely online in NI forum, that why) to look into your issue & help you out. Just a suggestion...

[Gak]

Hi Raghunathan,

I saw your vi. Make the 'Function code = Read Input register " instead of holding register. Other possible reason could be the starting address.

Hopefully this will solve your problem.

[Gak]

Hi parthabe,

I would like to ask question to you that is not related to this post. Do you have opening in TCS? 

Sorry if you don't like me asking this question.

[parthabe]

Hi Gaurav,

Please mail me directly to my ID in my reply post earlier.