Why serial communication fault?

[wemar146]

Hi labview users,

I have so much time working with Labview but and I haven't this problem before, I made a supervisory VI to monitoring and control the complete operation of a conveyor oven, the motors are controlled throught Siemens S7-200 PLC with modbus VIs, and the temperaruture controllers UT351 of YOKOGAWA are comunicating whit modbus too, the VI works ok but sometimes the comunication faults in ramdon mode, and because in ech scan I don't tracing the error signal the comunication should restart but it does'n happens until I restart the complete program or make, I tried aplying a "Clear" at the end of each iteration and the comunication restart automatically but the lost of comunication still happens and despite it's just a instant and almost the operator does not realize that the chart graphics shows a zero point int the lines.

Please I don't know if someone else had this problem before, I am waiting for your advices.

thank you in advance for your support,

WEMAR146

[muks]

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but sometimes the comunication faults in ramdon mode,

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Just a guess. Can it be a cable fault?

[Albert.Geven]

In this case I don't believe in hardware cabling errors but, EMC problems can generate sometimes such behavior, or water in connections where moisture comes down on too heavily cooled areas.

[wemar146]

Hi Albert, I thought about EMC too, but it can not be because as I said before I don't following the error signal so in the next scan it would restart the communication but it does not happens until clear or reinitialize the port, for example now I am making a clear to the port at the end of each scan and the communication fault and restart in the following scan it’s very fast but cause a cero point in the trend graphs..

Regards...

[muks]

Can you post a screen shot of your vi?