An analog module uses A/D and D/A converters.

• A. True
• B. False
• C. A/D only
• D. D/A only

Answer: (A)

An analog module is designed to bridge the real world of continuous signals and the PLC’s digital processing. To read a sensor that provides a voltage or current signal, the module uses an analog-to-digital converter to turn that continuous signal into a digital value the PLC can process. To control an actuator that expects a continuous signal, the module uses a digital-to-analog converter to convert the PLC’s digital output into an analog level for the actuator. Many analog I/O modules include both directions of conversion so they can handle sensors (A/D) and actuators (D/A) on the same card. So, it’s true because interfacing with real-world analog signals typically requires both conversion paths. In some cases you might have only input or only output, but the statement reflects the common capability of mixed analog modules.