Control Systems — question 10 of 10
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The controller reads an ADC, runs fixed-point PID math, and outputs to a PWM-driven heater.
A digital PID temperature controller runs comfortably within its computed stability margins and its step response looks textbook on paper. In practice, once it reaches steady state, the temperature never quite settles — it ticks up and down by a fraction of a degree in a tight, perfectly repeating pattern that never damps out, forever. Bode analysis says this loop should be stable. What's likely causing a persistent oscillation in a loop that's mathematically stable, and what would you check or change to fix it?