Simulated vs real waveform signal diference

[laboras]

Hi,

I am using cRio-9012 with Labview 2014 and create pid on-off air heater vi. System include temp sensor pt100 and thin metal plate with heating element. Heating element are operated by on-off relay. Apply step input like 60 in steady state at 20 degree (in real - step input are 1 or 0 because controller work as on-off switch) and read temperature when temp stop rise and nearly became stable at 84 degree in open loop mode, that value are max what heater can produce. Then determine transfer function with time delay. Time delay are 30 sec. and transfer function will be 64/410s+1 with step input 1. When that data add to simulated vi transfer function waveform graph are different from real time graph.  Where is problem? Real time waveform graph at the start rising are exponential. 

[GerdW]

Hi laboras,

When that data add to simulated vi transfer function waveform graph are different from real time graph.

Your simulation is off by less than 2% (363K vs. 357K) - so what's the problem?

 Where is problem?

Wrong expectations? 😄

Can you show your VI - instead of just two graphs?

[laboras]

Hi,

thanks for reply anyway, so first I run system in open loop mode with step input 60 degree all control are off so temp rise to max 84 degree that a max of heater output and that value every time nearly same. Disturbance are in my thing minimal because in my room steady state temperature are 20 degree and in system are second temp for info purposes. System start run at steady state 20 degree every time. Also heater time delay are 30 sec. I take the graph, do calculations, type in data to simulated system transfer function  and compare real

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with Simulated graph and that are different. One more think real time system are sync with cRio and looks like are correct, in simulation part also looks timing all ok just transport delay time in simulation part are not correct, has to be 30 sec but when run system 30 sec became about 300 sec. I fix that by experimenting and finding that must be 2,5 Sec. For that strange thing a create separate vi. Same thing, maybe are problem with timing? 

I uploading vi tonight for investigation.

[laboras]

Attached vi and subsystem files. Main .vi are my vision in  heater controller. 

[RavensFan]

English lesson:

"are" is the verb for plural nouns.

"is" is the verb for singular nouns.

[laboras]

English is not my native language, sorry.