A set of thermocouples would most likely be connected to a PLC through a(n) ______.

• A. Analog input module
• B. Digital input module
• C. Special module
• D. Relay output module

Answer: (C)

Thermocouples produce very small millivolt-level voltages that vary with temperature and require signal conditioning before a PLC can digitize them accurately. To handle this, PLCs use interfaces designed specifically for thermocouples—specialized input modules that provide cold-junction compensation, type calibration (K, J, T, etc.), amplification, and proper scaling to engineering units. This specialized thermocouple input module is the most appropriate way to connect a set of thermocouples, because it includes the necessary conditioning that a plain digital input, a relay output, or a generic analog input module would not inherently provide.