Smart Transmitters are advancement over conventional analog transmitters. They contain microprocessors as an integral unit within the device. These devices have built-in diagnostic ability, greater accuracy (due to digital compensation of sensor nonlinearities), and the ability to communicate digitally with host devices for reporting of various process parameters.

The most common class of smart pressure transmitters incorporates the HART protocol. HART, an acronym for Highway Addressable Remote Transducer, is an industry standard that defines the communications protocol between smart field devices and a control system that employs traditional 4-20 mA signal.

Parts of a Smart Transmitter:
To fully understand the main components of a smart transmitter, a simplified block diagram of the device is shown below:

Fig A Block Diagram of a Smart Transmitter

The above block diagram is further simplified to give the one below: 

As shown above in fig A, the smart transmitter consists of the following basic parts:
(a) Process Sensor
(b) An Analog to Digital Converter(ADC)
(c) A Microprocessor
(d) A Digital to Analog Converter(DAC)

These basic parts can be organized into three basic sections as shown in fig B:
(a) Input Section
(b) Conversion Section
(c) Output Section