Siemens S7-300 - Principles of HART Operation

Analog modules
9.3 SM 336; F-AI 6 x 0/4 ... 20 mA HART
Fail-safe signal modules
Installation and Operating Manual, 01/2010, A5E00085586-10
279
9.3.16.3 Principles of HART operation
Introduction
The HART protocol describes the physical form of the transfer:
● Transmission procedures
● Message structure
● Data formats
● Commands
HART signal
The following figure shows the analog signal with the HART signal modulated on it (FSK
technique). The signal is composed of sine waves of 1200 Hz and 2200 Hz. It can be filtered
out using an input filter so that the original analog signal is available again.
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Figure 9-43 The HART signal