How do multiplexers work in data acquisition systems?

Multiplexers (MUX) allow single ADC to measure multiple channels sequentially. Types: analog MUX (selects one of many analog inputs), digital MUX (selects digital channels). Design considerations: switching speed (settling time after channel change), channel-to-channel isolation (crosstalk), on-resistance (affects accuracy), charge injection (causes errors after switching), and break-before-make vs make-before-break switching. Sample-and-hold needed if signal changes during conversion. Throughput calculation: total time = (settling time + conversion time) x number of channels. Anti-aliasing filter per channel prevents inter-channel aliasing.