Practical Way to Find Transfer Function

[mohammadyou]

I wonder to know how can I find transfer function of a system by experiment (for example a heater ).
is it possible for different data we acquire the output and by thereof we get the transfer function?
Thanks

 

[AdvaRes]

Hi,
Its the response of the system when it is stimulated by a dirac impulse.

https://www.cs.unm.edu/~williams/cs530/eigen3.pdf

 

[FvM]

In a real world, a short rectangular pulse would be used instead of an ideal dirac impulse. A heater is an example of a system where it might be impracticable because the response to a short pulse of maximum input power is too low to measure the transfer function with sufficient signal-to-noise ratio.

Generally the transfer function can be determined as correlation of input and output signal if the input signal stimulates all characteristic frequencies of the system. A pseudo random sequence can be e.g. used as a wide band stimulation.

 

[mohammadyou]

Thanks advares and thanks fvm
in my case i want to use power line (220V 50Hz) to supply the heater and i can have different average voltage. For each of these voltage i have fixed temperature after some peroid of time. If i make a table for these values. Can i get the transfer function and how?

 

[hi_hedonist]

It is not clear though what are the I/O of transfer function. furthermore transfer function is for linear systems so you have to operate your system in linear range. good luck

 

[mohammadyou]

Thanks hedonist
the input is voltage and the output is temp. The problem is how can i do this. For different voltage the response of the system is get alter and it affect the max temperature that we can get and the time of reaching to that point

 

[hi_hedonist]

ok you need to use matlab. In matlab just type iduidemo. for more help **broken link removed**

 

[mohammadyou]

Thanks hi_hedonist that is so usefull