Expert’s answer: FOUNDATION Fieldbus or HART?

Hi! So, you want to know if you should go for FOUNDATION Fieldbus or HART? Ok, let’s review both technologies. Then you can consider my advice and read the links for more information about which will suit your needs best.

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HART

In multidrop installations, HART protocol is rare in the field. While you can have up to 15 devices installed in parallel, with multidrop you don’t have the variation of 4-20mA or the current fixed at 4 mA. You only have the HART information.

You can have two masters in the HART setup, the control system as the first and usually a handheld as the second, and each device will have a non-zero HART address. You’ll sometimes find this rare system when you have more than one device on a wirelessHART adapter.

You’ll also find two standard setups for HART. The first uses a HART card in the programmable logic controller (PLC) or distributed control system (DCS). Keep in mind that this doesn’t mean that the HART does the loop process control. It only uses the intelligent device management (IDM) in a plant asset management (PAM) system.

Two Masters in HARTThe second setup reads the current value and has a multiplexer among the field devices and the PLC, to catch all the HART data and send it to the system. This is typical because it makes the current loop a robust and straightforward installation.

One last option is setting a HART over other digital protocol; you can have HART over PROFIBUS  or HART over EtherNet/IP. This way, you have HART field devices and an input/output in the field sending data to the system digitally. You can save money with this setup because the protocol needs fewer cables than a traditional current loop installation.

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FOUNDATION Fieldbus

The FOUNDATION Fieldbus (FF) is the most common digital protocol in major oil and gas companies around the world. It differs from HART in that it provides digital access to the analog signal, and companies usually use it only for IDM. The FF offers many advantages over a traditional installation, giving the same smart device management with digital closed-loop control. The traditional system typically uses the 4-20 mA to do the loop control instead of a HART. With the FF, the system uses the protocol for the control and the IDM.

FOUNDATION Fieldbus or HART
Furthermore, the FF comes in High-Speed Ethernet (HSE) and H1. In the HSE version, you have ten megabits per second to integrate high-speed controllers, subsystems, servers, and workstations. The H1 link has 31.25 kilobits per second to connect field devices as sensors, actuators, and input/output. Unlike 4-20 mA and HART, the FF allows multiple variables from each device. The H1 also allows many devices to connect to a single wire pair, reducing the cost of installation.

The FF HSE is the same protocol that you have in the field, but with its high velocity, you can have field devices in the network as well as controllers, subsystems, data servers, workstations, and more. You can also set up redundant systems and equipment for backups.

Conclusion: FOUNDATION Fieldbus or HART?

Let’s recap, which one is it: FOUNDATION Fieldbus or HART?

If your plant has a new project, you should consider a digital protocol. In that case, an FF solution will provide more benefits than a traditional setup. On the other hand, if your company already has 4-20 mA, you can switch all your networks to FF or install wirelessHART to have easy and secure remote access. In either case, digital communication like FF will probably serve you best.

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Read more about the protocols:

And more about FOUNDATION Fieldbus:

Other resources that might interest you

Handheld and HART
Should I always have a 250-ohm resistor to use the handheld communicator with a HART device?

HART Communicator: When to Use
With a local configuration, when do you use the HART communicator?

Can I have a FOUNDATION Fieldbus wireless device?
Which device can go wireless, FOUNDATION Fieldbus or HART?

HART over FOUNDATION Fieldbus
Can a converter or a gateway connect a HART device in an FF network without data loss from the field devices, or do you have to stay with a HART over PROFIBUS remote IO?

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