In control engineering, compare analog versus digital controllers: do they cost the same to build, accept exactly the same input signals natively, and allow changes with equal ease?

Introduction / Context: Analog and digital controllers both regulate processes, but they differ in implementation, interfacing, and maintainability. This question probes three common misconceptions: identical cost, identical input handling, and equal ease of change. Recognizing the distinctions helps engineers choose the right controller for a given application, budget, and maintenance model.

Given Data / Assumptions:

• Analog controllers work with continuous-time signals and continuous internal behavior.
• Digital controllers sample sensors, run algorithms in discrete time, and output via DAC/PWM.
• Industrial sensors may output analog voltages/currents or digital/fieldbus signals.

Concept / Approach: We evaluate each statement against practical engineering realities, not edge cases. Costs depend on components and scale; inputs may require conversion stages; and configuration/change workflows diverge (hardware tweaks for analog vs firmware/parameters for digital).

Step-by-Step Solution: 1) Cost: Analog builds can be inexpensive for simple loops; digital can be cheaper at scale or when features (logging, networking) are needed. Costs are not “the same.” 2) Inputs: Analog accepts continuous signals directly; digital typically needs ADCs or digital buses. They do not accept “the same inputs” natively in all cases. 3) Ease of change: Analog often needs component swaps or trim; digital changes are parameter/firmware edits. They are not “equal” in ease or modality. 4) Therefore, none of the three assertions holds universally.

Verification / Alternative check: Controller datasheets and integration guides reflect these differences: ADC/DAC stages for digital, trimmers/gain networks for analog, and divergent cost structures depending on feature sets and volume.

Why Other Options Are Wrong: Option A: Cost parity is not a rule; it varies widely.
Option B: Native input compatibility differs; conversion is often required.
Option C: Change workflows differ; digital usually enables easier reconfiguration.
Option D: If any statement is false, “All” cannot be correct.

Common Pitfalls: Assuming that adding ADC/DAC erases differences; sampling, quantization, and configurability still diverge. Also, ignoring lifecycle costs (support, updates) skews comparisons.

Final Answer: None of the above