Tracerco Optimus T221, Operation Manual, Page: 19 / 32

MD1064 Rev. F 19 of 32
6 Operation
6.1 Passive 4-20mA Current Loop
The passive 4-20mA current loop always represents the system level independent of build-
up on the vessel walls. This is the same value that is presented as the primary variable on
the HART 7 interface.
The passive 4-20mA current loop output is required to be connected to an active 4-20mA
input that provides power for the current loop.
6.2 HART 7
HART 7 communication is available over the 4-20mA loop. To communicate with the
Optimus™ control module you require either a HART 7 active DCS or a HART modem an d
PC with the Tracerco ToolBox software.
The following sections provide the basic HART information required to obtain status
information from the device. For a complete description of the HART implementation
please refer to Tracerco document TD1071 T221 HART Field Device Specification.
6.2.1 Device Variables
The Optimus™ controls module supports 151 Device Variables. The table below provides
a summary.
Note: Channels are numbered from the bottom up. Also, GM tube counters within each
channel are numbered from the bottom up.
Number Name Classification Unit Codes
0 Process Level Analytical (81) Percent (57)
1 Maximum Build Up Length (69) cm (48)
2 Elevation of Maximum Build Up Analytical (81) Percent (57)
3 Average Gas Phase Build Up Length (69) cm (48)
4 Average Total Build Up Length (69) cm (48)
5 Process Level by Traditional
Calculation Analytical (81) Percent (57)
6 Radiation Source Strength Analytical (81) Percent (57)
7-78 Normalised Stage Count Rates (Up
to 72) Not Classified (0) None (251)
79-150 Build Up per Stage (Up to 72) Length (69) cm (48)
Table 5. Device variables.
6.2.1.1 Device Variable 0 – Process Level
This Device Variable has a fixed mapping to the Primary Variable. It represents the process
level and is resistant to: