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Operation LXT-220 DO
Teledyne Analytical Instruments 38
a function with its own manual mode output. The 4-20 assignment
display will show if the output is associated with an assignable manual
mode. Regardless of the cause, the affected operational display manual
mode fields will begin with a question mark when a conflict exists.
When that happens refer to the manual mode configuration displays, and
the question marks there will show where the problem lies.
No contention occurs unless two different displays are actually in
the manual mode for the same 4-20, so the question marks in the
displays can be ignored if the assignments are made for diagnostic
purposes.
3.3.4 HART Output Assignments
If the instrument was purchased with the HART option then the
next five displays are for assigning the HART digital and analog
outputs. The first of these displays is:
where… represents one of the items from the 4-20 mA assignment
list in Section 3.3.2.
HART command #3 requests four variables from the instrument.
Each of these variables can be assigned to any of the sources shown in
the 4-20 assignment section. Each variable has a units code, which
identifies the variable as being pH, millivolts, degrees C, etc. The units
code is supplied automatically depending on the assignment and the
instrument configuration. If command 3 is not used then only the first
output assignment will be reported. If any output is assigned to
“missing” or “unused” then that value will be reported as “not a
number”, and the units field will be “not used”.
HART analog 1:
The first digital output assignment is referred to as the primary
variable in the HART system.
HART 1: …..