Estimation of transfer function

Hello,

I'm trying to control 220V 100 Watt "Band Heater" by creating PID controller to apply 160 degree celsius on load, So in order to set PID gains i need to determine Transfer Function of band heater, I applied 220V to the heater and record the output temperature (using thermocouple) in array and send the records to MATLAB, but there was a problem when i tried to estimate transfer function, MATLAB asks me Number of poles and Number of zeros, and i couldn't actually determine them, So my question is:

What could be the number of poles and zeros for this system (Band Heater)?

Thanks.

[Ameer Hamza]

Duplicate of: https://www.mathworks.com/matlabcentral/answers/518802-estimation-of-transfer-function