What is the purpose of a HART master in a network?

• A. To initiate communication, poll devices, read/write variables, and configure devices.
• B. To power the loop and never communicate with devices.
• C. To store proprietary firmware only.
• D. To act as a slave responding to another master.

Answer: (A)

In a HART network, the master is the controller that initiates communication with field devices on the 4-20 mA loop. It polls devices, reads and writes process variables, and configures devices, managing data collection, diagnostics, and setup. The loop current powers the instruments, while the master handles the digital commands that sit on top of that analog signal, whether the master is a handheld device or a control system. The other descriptions don’t fit because the master isn’t only a power source with no communication, it doesn’t merely store firmware, and it isn’t a slave that responds to another master—the master directs and drives all communication.