How to select I/O module isolation devices

Selecting isolation devices for I/O modules requires comprehensive consideration of isolation type, performance parameters, and cost. First, determine the type of signal requiring isolation: for digital signals, optocouplers, magnetic couplers, or capacitive digital isolators are used; for analog signals, isolation amplifiers, isolated ADCs, or V/F converters are selected. Key parameters include: isolation voltage (typically 1.5kVrms to 5kVrms for industrial applications); data transmission rate (for digital isolators, the communication baud rate requirement must be met); common-mode transient immunity (higher is better, e.g., 100kV/μs); and power consumption and temperature range.

For optocouplers, current transfer ratio and aging characteristics also need attention. Multi-channel isolation devices can save space when layout is limited. In terms of cost, optocouplers are generally the most economical, while high-end digital isolators and isolation amplifiers are more expensive. Reliability certification and long-term supply stability of the devices should also be considered during selection. Ultimately, a comprehensive trade-off should be made based on the isolation withstand voltage, signal bandwidth, accuracy requirements, and cost budget for the application scenario, and the actual performance under EMC conditions should be tested by building a prototype circuit.