profibus

[teh]

Hi Friends,

Have anybody faces this problem before? the reading of scada(citect)
showing -negative value while the setting ranging is 0 ~ 200 deg c ( 0 ~ 27648 ). PlC i am using S7 300. The - negetive value appear not very frequence, several times per day, and funny thing is only occur to my temperature analog signal but not level, pressure signal.

Is that because of i am using s7 profibus for communication?
i dunno this kind of system is suitable for communication or not.

Thanks

 

[drewcrew6]

Are you sure the reading isn't coming from the actual device or is it truly a profi-bus communications problem?

I never dealt with any of that but it may help someone else answer.

Drewcrew6

 

[rajendrad]

Hi,

I faced similar type of problem recently.We had Siemens PLC and MMI on profibus.Analog inputs are all showing negative or zero value. But I found this is due to combination of problem - 1.position sensor problem 2. Voltage drop problem. Is it possible you to check the voltages ?

 

[nif]

Hello !
Have you checked the temperaturegauge ? If you use thermocouples you can get that kind of problems ! What about the kompensation "resistor"?

If you have pt 100 maybe it's broken ?

That problem should have nothing to do with profibus communication, it's just easy to always blame the fieldbus..