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• HART Device Status - A collection of status indicators that reflect the
HART communication details and overall device health.
– Init - Module is searching for a HART device.
– Fault - HART communication is not successful. If this is 1 and
Initializing is 0, probable cause is HART is not enabled on this channel.
– Message Ready - A HART pass-through message reply is ready to be
collected by using the Pass-through Query CIP message. For
information on using CIP MSGs to access HART data, refer to the
ControlLogix HART Analog I/O Modules User manual, publication
1756-UM333.
– Current Fault - The analog current doesn't match the readback of the
current received over the HART communication. This might be caused
by an inaccurate field device, faulty wiring, or water in the conduit.
Sometimes a rapid change in the signal results in a transient current
fault as the analog and digital representations are sampled at slightly
different times and at different places in the signal path.
– Configuration Changed - The Field Device configuration has changed
and new Field Device configuration information can be obtained from
the module via CIP MSG GetDeviceInfo, which will clear this bit.
– ResponseCode - HART Communication Status or Response Code.
0 means success.
– FieldDeviceStatus - HART device health, such as PV out of range or
device malfunction. See
– UpdatedStatusReady - indicates new device diagnostic information is
available, which can be obtained by sending a CIP Message with
Service 4C.
HART Dynamic Variables
Most HART devices are capable of measuring several different process
characteristics or of deriving other measurements from directly sensed
measurements. For example, many differential pressure transmitters can also
sense the process temperature and can calculate the flow, or they might calculate
the volume in a tank based on a measurement of its head pressure and knowledge
of tank geometry and product density.
The most important of these direct or derived measurements is assigned to the
PV (Primary Variable) and the analog signal will represent its value. Additional
measurements can be read from the HART field device over the HART
communication protocol. HART provides a standard message for reading four of
the dynamic variables, called PV, SV, TV, and FV (sometimes called QV). These
four dynamic variables are the four measurements of interest to a controller.
These four dynamic variables - PV, SV, TV, and FV - are automatically collected
from the HART field device and placed in the module's input tag in
HART.ChxPV (for Analog and HART PV data format) or Chxx.PV (for Analog
and HART by Channel data format). In some HART devices, the choice of
which of the available measurements to assign to PV, SV, TV, and FV can be
Rockwell Automation Publication 1719-UM001C-EN-E - August 2018
1719 Ex I/O HART Analog I/O Modules
Appendix C
for details.
Chapter 5
51
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