5.1 Designing a Multi-Channel 4-20mA Analog Input Module
with Lars Lotzenburger
Analog input modules for programmable logic controller continue to enjoy unbroken attention at our customer with the highest growth potential among all other module types. A wide variety of modules with different analog input types, performance-levels, channel densities and safety requirements are available on the market today.
This training helps to understand relevant parameter of a 4-20mA analog input module, such as surge protection, handling miss-wiring, broken wire detection, isolation or protection of the module against over-current at power and signal inputs. First, the proper burden resistor will be selected and different connection options to the high-precision delta-sigma analog-to-digital converter ADS114S08 will be presented. Next, the proper configuration of the ADC will be discussed to achieve maximum resolution at a given sampling rate. Several power tree options are discussed. Finally, all piece are put together to show a possible solution of such a 4-20mA analog input module.