Book Analog Interfacing to Embedded Microprocessors
block is too cold, it takes a while for the heater to heat up, then for the load
to heat up, then for the thermistor to respond to the change. In the mean-
time, the microprocessor has sampled the thermistor many times, found that
the temperature still isn’t right, and pushed the output even higher. Or, in an
on-off control, the heater stays on well past the optimum point for the right
temperature, resulting in overshoot and oscillation. In either case, the con-
troller overcompensates for the error. Using PID control instead of just pro-
portional control can reduce some of these effects, as we have already seen.
However, in some cases, PID control can make a deadtime situation worse,
such as when windup occurs.
Compensating for deadtime usually involves predicting the effect of a
control change and assuming that it will take place after the deadtime has
elapsed. Once the real result of the change is available, a new change can be
annaabi.ee 
