Hello, I have been obsessed with PID control concept and i want to notice you my doubt here. PID controllers are very useful in industrial applications to make the error free process(learned from the web). Basic PID controller mechanism is to tune the values P(Proportional gain), I(Integral gain from the recent errors) and D(derivative gain on about future errors) that are useful to minimize the error after the measured process. That means, the set point(SP)(before the operation) and the measure value(MV)(after the operation) should be same. My concerns about, i) If you tune P,I and D values to make both SP and MV same, Is that real process was done with some error plus set point value. Here i have been messed up and did not understand well how and where these tuning was done(at last stage of the process to just show SP and MV are same or starting of the process?). Any help! Thank you.