What is the advantage of digital PID controller vs a analog PID?

Answer 1

It is far easier to tune a digital PID controller, than an analog controller. To tune an analog controller, requires multi-turn potentioneters and a lot of actual "tweaking" of those pots. Occasionally you need to change out capacitors in an anlog controller, too. Once pot. values have been fixed, and permanent resistors have been soldered in place, there is amplifier, resistor, and capacitor drift to contend with. Analog systems sometimges require precision-valued components, which are expensive.

In a digital system, all you have to do is re-compile some code with the new coefficients coded in. This takes less time, and less effort (than soldering, picking component values, etc.)

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Answer 2

Analog Pid Controller

Answer 3

In general digital systems are more imune to electric interference, and are far less prone to drift in calibration.
They are essentially more reliable.
Digital controllers can generally communicate with a centeral computer through a digital comunication bus. They can often also be configured and tuned using the same bus (one does not have to phsically go to each device to calibrate and tune it as is the case with analogue controllers).

Times have changed. Digital controllers are becoming less expensive than analog controllers as well.

The trend is to make everything digital.