How do PLCs handle analog input and output signals?

PLCs interface analog signals through dedicated I/O modules. Analog inputs accept: 4-20 mA, 0-10 V, thermocouples, RTDs, or strain gauge signals. The module contains: input protection, signal conditioning, multiplexer (to share ADC), ADC (typically 12-16 bit), and isolation. Resolution depends on ADC bits and input range. Analog outputs generate 4-20 mA or 0-10 V using DACs. Configuration includes: input type, engineering units, scaling, filtering, and alarm limits. Scan time affects how often signals are updated. Proper wiring (shielded cables, separate from power wiring) is critical.