Fluid Components International ST100 Series HART - Manual (Page 9)

ST100 Series HART
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Operation
Functional Description
The primary function of the HART protocol is to present the instruments process data through its process data commands. Command 1, command 3
and command 9.
The ST100 does not implement the HART Burst mode. A HART master that supports HART 7.0 and higher is required. A HART communicator that
supports HART 7.0 and higher is required (i.e. Emerson 475 Communicator.)
Process Data Operation
Even though HART 7.0 is compatible with older versions of the HART protocol, the ST100 HART implementation and commands 1 and 3 are still sup-
ported, they contain the Flow Variable only, for the full set of Dynamic variables it is recommended that the HART master use command 9 to request
process data of dynamic variables and status.
ST100 HART Process Data Organization
It is important to briefly review how the ST100 Process data is organized under the HART command 9. For Details on Command 9 see the HART
Specification “Universal Commands Specification” HCF_SPEC-127, Revision 7.1.
Not all the variables described in this section are available in all configurations of the ST100 flow meter. For example not all configurations have
Process Pressure, and instruments that output Mass Flow or Volumetric flow , the Flow Totalizer may be turned on or off.
The following are the ST100 process variables that are provided through HART command 9.
There are 3 flow classes or types, and these are “Exclusively OR” meaning that only one class of flow is active at a time.
PROCESS VARIABLE SLOT #
HART VARIABLE CODE
DESCRIPTION
DEVICE VARIABLE CODE
DEVICE VARIABLE
CLASSIFICATION
VOLUMETRIC FLOW * 0 PRIMARY VARIABLE 0 66
MASS FLOW * 2 PRIMARY VARIABLE 2 72
VELOCITY FLOW * 4 PRIMARY VARIABLE 4 67
VOLUME (TOTALIZER) 1 SECONDARY VARIABLE 1 68
MASS (TOTALIZER) 3 SECONDARY VARIABLE 3 71
TEMPERATURE 5 TERTIARY VARIABLE 5 64
PRESSURE 6 QUATERNARY VARIABLE 6 65
* Implies an “Exclusive OR” Releationship
Under the “Device Variable Status” parameter, for each process variable, only the four most significant bits are used.
The two most significant bits contain
“Process Data Status”:
11 = good
01 = Poor Accuracy
10 = manual/fixed
00 = bad
The two bits after the two most significant contain
“Limit Status”:
11 = constant
01 = low limited
10 = high limited
00 = not limited
Device variable status example: 1100XXXX.X, variable values indicated in positions represented by an ‘X’ can be ignored.