Dear Brian,
Thank you for your reply. You are right. The output limits must be 0% to 100%. I will add the cooling module after stabilizing heating source. I've used a kapton thin-film heater. It is very small. I've tried to autotune, but it cannot be stable the temperature. I've attached the processing picture. The hardwares are Fieldpoint 1000 with TC-120 and PWM 520, external power supply connected to PWM module, and a small heater. I've got PID parameter from autotuing function, P = 241, I = 0.421, and D = 0.105.
Thanks,
Tae Yoon Lee