13.4.2 Smart sensors
Smart sensor is a name given to the integration of the sensor with an ADC,
processor, and DAC for actuator control and the like; such a setup for furnacetem perature control is shown in Fig. 13.11. The electronics in the smart sensor
contains all the circuits necessary to interface to the sensor, amplify the signal,
apply proportional, integral, and derivative (PID) control (see Chap. 14), sense
temperature to correct for temperature variations in the process if required, correct
for sensor nonlinearity, the ADC to convert the signal into a digital format
for the internal processor, and the DAC to convert the signal back into an analog
format for actuator control. The processor has a serial digital bus interface for
interfacing via the fieldbus to a central computer. This enables the processor in
the smart sensor to receive update information on set points, gain, operating
mode, and so on, and to send status information to the central computer.