PID on temperature control

I have questions regarding using PID on temperature control of a packing machine.

How you can determine the sample time of PID?

How you should you adjust the BIAS term. Normally if you change setpoint and do not reset the bias term, bias causes overshoot for the new setpoint.

For PID control of temp. systems I read different approaches. To change the setpoint over time instead of cahnging setpoint instantly, to create a band to use PID around setpoint or to deactivate the integral term for the PID output over some level.

Thanks

GOKALP,

You might want to try Ron's post HERE for some answers.

Andrew