What are the different techniques for signal isolation?

Isolation techniques: Optical (optocoupler) - LED-photodetector pair, good for digital signals, limited analog accuracy. Transformer - magnetic coupling, excellent for AC and modulated signals, very high isolation voltage. Capacitive - charge coupling across barrier, good high-frequency response, lower isolation voltage. Galvanic isolators (specialized ICs) - combine techniques with integrated signal conditioning. Selection factors: isolation voltage rating (typically 1-5 kV), bandwidth, accuracy (linearity, drift), common-mode rejection, and power requirements. Transformer isolation common for 4-20 mA loops; optical for digital; specialized ICs for precision analog.