Abstract

Designing programmable logic controller (PLC) analog input modules requires the engineer to balance multiple, often conflicting parameters. Analog input module designs must offer flexibility to support different process signal types and ranges, include multiple inputs for high channel-count systems, enable high-accuracy measurements, and result in a cost-competitive design. This complete, pre-tested front-end design for analog input modules saves development time while demonstrating input flexibility and high-accuracy measurements. Additionally, comparing the 1000-unit cost of this discrete design (without the TPS26611 protection circuit) to a more integrated solution shows that the discrete solution cost is about half. The channel cost is about $0.89 for the discrete solution, which drops further if more analog input channels are added.