Rockwell Automation T3431-CA ICS Regent Thermo Couple Input Assembly - Manual (Page 22)

Thermocouple Input Assembly (T3431)
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Industrial Control Services
Programming Fault Tolerant Thermocouple Inputs
To program fault tolerant configurations using triplicated
thermocouple input modules, a midvalue element can be used
as shown in Figure 14.
Figure 14. Programming Fault Tolerant Thermocouple
Inputs.
In this illustration, VALUE_A_NAME, VALUE_B_NAME,
and VALUE_C_NAME represent the three thermocouple
inputs to be mid-value selected. ERROR_A_NAME,
ERROR_B_NAME and ERROR_C_NAME are the error bits
for the T/C inputs. RESULT_NAME is the result of the mid-
value instruction. The field Limit is the integer value, in
similar units to the Value A, B and C variables, that a
thermocouple input can deviate from the mid-value result
before signaling an error (via the Error A, B or C bits). Once
an error bit is set, it is latched. RESET_NAME is the reset bit
used to reset the latched error bits.
Thermocouple Burnout and Out of Range Conditions
The NOSIG contact in ladder logic function blocks can be used
to detect an out of range thermocouple input signal. The
NOSIG contact will be true if the thermocouple input reaches
the limits of its usable range (see Table 2, Temperature Data
Ranges). The temperature value will be equal to the lower or
upper limit value listed in the table for maximum data range
while the temperature remains out of range.
Note: For Type K and S thermocouples, the maximum
input value is clamped at 16383 due to data format
limitations. The NOSIG contact will not be true until the
thermocouple signal reaches the maximum upper limit
value defined in Table 2.