🔍 Key Concepts

• ADC (Analog-to-Digital Converter) vs DAC (Digital-to-Analog Converter) – what do they tell you about the type of signals on each side of these blocks? • What a PLC (Programmable Logic Controller) is made of (is it more like a computer chip or an analog circuit?). • Difference between analog signals (continuous) and digital signals (discrete/binary or numeric).

💭 Think About

• Look at where the set value and actual value enter the system in figure A. Are they on the same side as the ADCs or the PLC? What does that imply about their nature? • Inside the PLC, the arithmetic processor is doing the math. Is that processor handling continuous voltages or numbers stored in memory? How would a PLC normally work? • Follow the signal path: process/measurement → ? → PLC → ? → actuator. At which points must the signals be analog to interact with the real-world process and sensor, and where must they be digital to be processed by the PLC?

✅ Before You Answer

• Verify which side of the ADC/DAC the set and actual values are drawn on in the diagram. • Confirm that a PLC’s internal processor operates using digital data (numbers, logic states) rather than continuous analog voltages. • Check that the measurement and actuator connect directly to the physical process, which typically requires analog signals at those interfaces.