TABLE OF CONTENTS This chapter will help you understand why signal conditioning is required in process control and to familiarize you with signal conditioning methods.
The following are covered in this chapter:
The conversion of sensor signals into pneumatic or electrical signals
Signal linearization, methods of setting signal zero level, and span
Nonlinear analog amplifiers
Digital linearization
The difference between sensors, transducers, and converters
Conditioning for local displays and transmission
Temperature compensation used in signal conditioning
Signal conditioning used with Hall effect and magneto resistive element (MRE) devices
Considerations using capacitive devices
Resistance temperature detectors (RTD) signal conditioning
Many sensors do not have a linear relationship between the physical variable and the output signal. Output signals need to be corrected for the nonlinearity in their characteristic, or conditioned for transmission to a central controller, or for direct control, so that the necessary valves or actuators can be operated to accurately correct for variations in the measured variable in a process control system.
Sensors are used to convert physical variables into a measurable energy form. This energy form is used to directly or indirectly give a visual indication, as an actuator control signal or as a signal to a controller. Signal conditioning refers to modifications or changes necessary to correct for variations in a sensor's input/output characteristics so that its output bears a linear relationship with the process variable being measured, and the signal is then suitable for use by other elements in the process control loop. Most sensors do...
