What is the maximum distance for Hart protocol?
What is the Maximum Distance for HART Protocol?
The HART (Highway Addressable Remote Transducer) protocol is a common means for process industries to talk to each other over the same 4–20 mA analog signal loop. One of the most typical inquiries engineers get when they are designing and installing is: How long may HART communication cables be?
In perfect conditions, the HART protocol can work up to 10,000 feet (about 3,000 meters) away. But in real life, the actual distance depends on the type of cable, its capacitance, and how well it was installed.
Cabling Considerations
- To reduce outside noise and interference, use high-quality insulated twisted pair cable.
- For routes shorter than 5,000 feet (1,500 meters), the smallest conductor size that is suggested is #24 AWG. To lower resistance, use #20 AWG or larger for longer runs.
- The integrity of the HART signal is directly affected by the cable’s capacitance. The maximum distance that can be reached gets shorter as capacitance goes up. For instance, if the capacitance is 83 pF/ft, the cable length that can be used may be cut down to 4,000–5,000 ft, depending on how it is set up.
Grounding Best Practices
- To avoid ground loops, the HART loop should only be grounded at one place.
- Cable shields should also be grounded at one point, preferably close to the power supply for the control system.
HART can technically support distances of up to 10,000 feet, but in the actual world, the distance will depend on things like cable capacitance, conductor size, shielding, and grounding. Following the HART physical layer requirements makes guarantee that communication works well in industrial settings.