tailieunhanh - Lecture Chemical process control - Chapter 9

a | Dynamic Behavior of Closed-Loop Control Systems Chapter 9 Figure Standard block diagram of a feedback control system. Control System Instrumentation Chapter 9 Figure A typical process transducer. Transducers and Transmitters Figure illustrates the general configuration of a measurement transducer it typically consists of a sensing element combined with a driving element transmitter . Chapter 9 Since about 1960 electronic instrumentation has come into widespread use. Sensors The book briefly discusses commonly used sensors for the most important process variables. See text. Transmitters A transmitter usually converts the sensor output to a signal level appropriate for input to a controller such as 4 to 20 mA. Transmitters are generally designed to be direct acting. In addition most commercial transmitters have an adjustable input range or span . For example a temperature transmitter might be adjusted so that the input range of a platinum resistance element the sensor is 50 to 150 .