HART theory: Sending a digital communication through an analog signal

Field Network Q&A

Could you explain how it's possible to send a digital communication through an analog signal?

Expert’s answer: HART theory

Yes, of course! You can find the answer on the HART Foundation website, which will give you all the technical details about the HART theory and communication. However, let me make your life easier and just give you the answer.

So, the HART protocol uses the Bell 202 Frequency Shift Keying (FSK) standard. That means the protocol can superimpose digital signals at a low level on top of the 4-20 mA output!

To keep it simple, the HART communication understands the FSK frequency of 1200 hertz as “1” and the FSK frequency of 2200 hertz as “0” digital values.

HART offers a wide range of possibilities. Oddly enough, most applications don’t use the digital communication, only the 4-20 mA! Nonetheless, there are different ways to pull all the smart information from the field. You can read more about that here.

Want more information? Then, check out these Wireless and HART solutions:

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