Although the digital transmission of data is a widely discussed technique in modern data-acquisition systems, many applications convey remote information effectively and economically using analog signals. In process control, controlled currents with spans of 4 to 20 mA or 0 to 20 mA carry analog data for long distances over two wires (0-to-20 mA loops need a third lead for power), representing such sensor variables as temperature, pressure, speed, or flow, with accuracy, reliability, and low-cost. Read full article
