Regarding PID control over FB41

Dear sir,

In on of our Extruder machine FB58 is used to control heaters temperature ,For measurement's of temperature thermocouple is used with AI8*12bit module.As per attached img others zone temp  controlling is ok,but for zone -1 set temp is 180degree and actual value coming is 268degree.

Cooling fan is being used for cooling heaters  if temp going above set limit. For zone-1 cooling fan is working ok. but still temp is going above set limit.Why??

I tried for autotuning but problem not resolved ,There is a HMI MP377 12 key communicating with cpu  315- 2 DP and in HMI there is a facility to do autotune.As mention i tried for autotune but it does not solve my problem.

One thing also when temp goes beyond set limit heater gets off but temp not decreasing.SSR is used to control heaters on/off operation.

Regards,

Pankaj Tiwari

 Dear sir,

That's the problem why temp is increasing.I tried to replace thermocouple with new one still problem is coming.

Also my cooling fan is working ok.

Regards,

Pankaj Tiwari

jacek d

So, your heater is off but temperature still rises and you think it's control software problem?

Use some other temperature measurement to check if readout of the thermometer used is correct.