Advantages of digital over analog control

A digital control system uses a computer or microcontroller as the controller. Compared with an analog (op-amp/RC) controller it has these advantages:

1. Flexibility: the control law is a program. Gains or the whole algorithm can be changed by software, without changing hardware.
2. Accuracy and stability of parameters: digital values do not drift with temperature, ageing or component tolerance, so performance stays repeatable.
3. Noise immunity: binary signals are much less affected by noise and interference than low-level analog voltages.
4. Complex control: nonlinear, adaptive, optimal, self-tuning and logic-based control are easy to code but hard or impossible with analog circuits.
5. Time sharing: one processor can control many loops through multiplexing, lowering cost per loop.
6. Data storage and communication: values can be logged, displayed, trended and sent over networks (SCADA, IoT); supervisory control is easy.
7. Cost, size and weight: cheap microcontrollers replace bulky analog hardware.
8. Reliability and diagnostics: self-tests, alarms and fault detection can be built into the software.
9. Wide dynamic range: limited only by word length, not by supply voltage.

Example: changing a furnace controller from PI to PID needs only new code and new gains in a digital controller, but needs new components and recalibration in an analog one.