HART vs FOUNDATION Fieldbus
Side by side comparison: how they work, where each fits, and which to choose.
Quick answer: HART adds digital data on top of a standard 4 to 20 mA loop and is simple; FOUNDATION Fieldbus is fully digital, multidrop and can run control in the field, but needs segment design.
HART vs FOUNDATION Fieldbus: Comparison Table
| Aspect | HART | FOUNDATION Fieldbus |
|---|---|---|
| Signal | 4 to 20 mA plus FSK digital | All digital, 31.25 kbit/s |
| Wiring | One device per pair | Many devices per segment |
| Speed | 1200 bit/s | 31.25 kbit/s |
| Control in field | No | Yes, function blocks |
| Engineering effort | Low | Higher |
| Diagnostics | Good with asset software | Rich and continuous |
Choose HART when
- Most plants, upgrades and mixed vendor systems
Choose FOUNDATION Fieldbus when
- Large greenfield projects aiming to reduce wiring
Key Differences Explained
HART keeps the robust analog signal for control and adds configuration and diagnostics. Fieldbus replaces the analog signal entirely.
Ethernet based approaches such as Ethernet APL are now emerging as another option.
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Frequently Asked Questions
What is the difference between HART and FOUNDATION Fieldbus?
HART adds digital data on top of a standard 4 to 20 mA loop and is simple; FOUNDATION Fieldbus is fully digital, multidrop and can run control in the field, but needs segment design.
Can HART devices work on fieldbus?
No, they are different protocols; gateways can bridge them.
Is HART slow?
For configuration and diagnostics it is fast enough; control uses the analog signal.
What limits a fieldbus segment?
Voltage at the farthest device, total current and cable length.
Learn more on the blog
HART protocol: how it works and how to use a HART communicator
A practical guide on instrumentationblog.in that goes deeper into this topic with field examples.
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