How many master devices can exist in one HART communication loop?
A. 1
B. 2
C. 3
D. 5
View Answer
Correct Answer: B: 2
Explanation:
In a HART communication loop, a maximum of two master devices can exist simultaneously.
These are:
- Primary Master → Usually the DCS, PLC, or control system
- Secondary Master → Usually a HART communicator or maintenance device
HART protocol supports dual-master communication, allowing both devices to communicate with the smart field instrument without interfering with each other.
For example:
- The DCS continuously reads process variables from a transmitter.
- At the same time, a technician can connect a HART communicator for configuration or diagnostics.
This dual-master capability is one of the important features of the HART protocol used in industrial automation systems.