n WinCC HMI signal some times goes to zero

we are using WinCC SCADA for data recording like temperature RH from & S7 300 PLC& Profibus DP for s7200.
we are using CP6513A2 card profibus communication protocol.
we are facing problem of Temperature signal value many times in a day goes to zero & again come to normal value. this 0 sugnal dip is for some times 2 second some times 5 or 10 seconds.
we have checked the signal cable and laid new cable for sensor we have also replaced the sensors. but still this problem is not solved.signal level is 4-20ma.
kindly give your suggestions to avoid this problem.

Aditya mishra

are there any other tags in Wincc you are having problems with or is it just from this device?? is this a new device which has been recently added to the system? does the diagnostics show anything in the plc when this happens?

5 -6 tags are there in which we are facing problem. we are using vaishala sensor for RH & temp measurement and in level sensor we also facing same problem. we think this is not related to sensor o/p. we are using these device from long time. no diagnostic is not showing any message. we have 10 profibus nodes which is connection to CP5613A2 card in WinCC SCADA.

Have you checked EventLog from PLC and Application EventLog from PC?
What kind of devices are in ProfiBus? In other words, how much traffic there are in proportion to speed.
In WinCC, are there C+ scripts?