GFK-1504K Chapter 14 Temperature-Sensing Modules 14-19
14
IC200ALG630
Analog Input, 16 Bit Thermocouple, 7 Channels
Diagnostics
The Thermocouple module performs diagnostics and provides the following information in
the I/O fault table.
Alarm faults are reported if the processed value for a channel exceeds its configured alarm
limit.
Over/underrange faults are reported if the millivolt value for an input exceeds the limits of
its span.
Open circuit is checked every time a thermocouple input is read (unless Open TC checking
is disabled). If the circuit is open, a fault is reported and the input defaults to the
configured channel default (this is 0 unless re-configured). If the Thermocouple Type
parameter has been configured as “none”, open circuit checking is not done.
After an Open Circuit fault condition is corrected, the module takes a few seconds to
return to normal operation. During this time, the module continues reporting the channel
default input value. After the module has recovered from the Open Circuit fault, it returns
to normal inputs and normal operation.
If there is a very large change in an input (for example, an input quickly goes from 50mV
to 400mV), the module may briefly report an Overrange fault on that circuit even though
the circuit is not actually over its configured upper range limit. This is only temporary.
Thermistor Fault
A thermistor fault occurs if the calculated temperature value from the thermistor is less
than -10 degrees C or greater than +75 degrees C.
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