what is hart communicater? can u give brief explanation
about this issue?
Answer Posted / manohar chotrani
HART® Field Communications Protocol is widely recognized as
the industry standard for digitally enhanced 4-20 mA smart
instrument communication. The HART protocol provides a
uniquely backward compatible solution for smart instrument
communication as both 4- 20 mA analog and digital
communication signals are transmitted simultaneously on the
same wiring. HART provides many benefits promised by
fieldbus, while retaining the compatibility and familiarity
of existing 4-20 mA systems.
Analog + Digital Communication
For many years, the field communication standard used by
process automation equipment has been a milliampere (mA)
analog current signal. In most applications the milli
ampere signal varies within a range of 4-20 mA in
proportion to the process variable being represented.
Virtually all installed plant instrumentation systems use
this international standard to communicate process variable
information.Simultaneous Analog + Digital Communication
HART uses Frequency Shift Keying to encode digital
information on top of the 4-20 mA analog signal
HART Field Communications Protocol extends the 4-20 mA
standard to enhance communication with intelligent
measurement and control instrumentation. A major step in
the evolution of process control, the HART protocol is
fostering significant innovation in process instrumentation
capabilities. The enhanced communication characteristics of
this important technology are reflected in the protocol
name, HART which stands for “Highway Addressable Remote
Transducer”.
The HART protocol enables two-way digital communication
with smart instruments without disturbing the 4-20 mA
analog signal. Both the 4-20 mA analog and HART digital
communication signals can be transmitted simultaneously
over the same wiring. Primary variable and control signal
information is carried by the 4-20 mA (if desired), while
additional measurements, process parameters, device
configuration, calibration, and diagnostics information is
accessible through the HART protocol over the same wires at
the same time. Unlike other “open” digital communication
technologies for process instrumentation, HART is
compatible with existing systems.
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