Thermocouple burnout detection, Installation planning – Rockwell Automation T3431-CA ICS Regent Thermo Couple Input Assembly User Manual
Page 14
![background image](/manuals/581443/14/background.png)
Thermocouple Input Assembly (T3431)
1 4
Industrial Control Services
T/C
Type
Scale
Lower
Limit
Upper
Limit
Lower
Limit
Upper
Limit
Lower
Limit
Upper
Limit
J
ºC
0
750
0
750
0.0
750.0
ºF
32
1382
32
1382
32.0
1382.0
K
ºC
-200
1250
-200
1250
-200.0
1250.0
ºF
-328
2282
-328
2282
-328.0
1638.3
S
ºC
0
1450
0
1450
0.0
1450.0
ºF
32
2642
32
2642
32.0
1638.3
T
ºC
-200
350
-200
350
-200.0
350.0
ºF
-328
662
-328
662
-328.0
662.0
Note for thermocouple types K and S: If a 0.1
°
F resolution is
selected, the maximum usable temperature is 1638.3
°
F.
Even though the range limit has not been reached, the value
will be clamped at 1638.3 because of word length limitations.
Changing the resolution jumper to units will allow the entire
data range to be passed without clamping.
Thermocouple Burnout Detection
Open thermocouple channels are automatically driven
downscale (downscale burnout). The temperature value will
be equal to the lower limit value for the particular
thermocouple type. An open circuit on either terminal will
cause a downscale reading. This is not affected by a ground
connection at the thermocouple.
In application programming, the NOSIG contact in ladder
logic can be used to sense the thermocouple burnout
condition. For more information, see Programming, starting
on page 21.
Installation Planning
Accuracy Considerations
Use the following guidelines to maximize overall system
accuracy:
1. Temperature gradients should be minimized at the
termination panel. Avoid forced air cooling or placing heat
dissipating components directly underneath the terminal