HART Protocol and 4–20 mA Loop Communication Fundamentals Practice Test

Digital data is information expressed with discrete states rather than a continuous range. Typically this means two distinct levels—on and off—which map to binary 1s and 0s. In the 4–20 mA loop used with HART, digital data is carried by switching the signal between these two states, encoding bits of information such as device diagnostics, configuration, or status, while the analog current continues to convey the actual process measurement.

The other descriptions describe analog behavior: a continuous range of values represents analog data; a signal that changes smoothly over time is analog; a measurement expressed as voltage levels could be an analog reading rather than discrete digital information.