VersaMax* Analog Input, 16-Bit Thermocouple Module
IC200ALG630
October 2016
GFK-1700L
5
Cold Junction Compensation:
The Thermocouple module provides
four choices for Cold Junction Compensation.
No Cold Junction Compensation: This is used for millivolt inputs or
if cold junction is maintained at 0 degrees C.
Remote Cold Junction Compensation: With this option, cold
junction is measured externally and provided to the module from
the application, via the module’s analog output (word output) data.
If the module has multiple thermocouples that are configured for
remote compensation, the same compensation value must be used
by each.
Fixed Cold Junction Compensation: This option uses a fixed
compensation value provided by the user in the configuration
parameter
,
“Reference Junction Value.” The units of this fixed
value are defined in configuration parameter “Engineering Units.”
Local Cold Junction Compensation: The best way to provide local
compensation is with an Interposing Thermocouple Carrier, which
has a built-in thermistor. Using an Interposing Carrier allows the
thermocouple connections to be placed farther away from the I/O
modules in the system, which helps shield thermocouple
connections from module heat.
If Local Cold Junction Compensation is configured and an Interposing
Thermocouple Carrier is not used, a separate thermistor must be
installed directly at the module’s I/O Carrier, using the Thermistor (+)
and Thermistor (
–) terminals. The thermistor must be the type specified
in the
I/O Modules User’s Manual
. Note: If Local Compensation is
selected but an Interposing Thermocouple Carrier or local thermistor is
not used, erroneous temperatures may be reported and a thermistor
error will be reported in the fault table.
Range Selection:
The module is configurable for any of six different
millivolt ranges (+/
–): 19.5mV, 39mV, 78.125mV, 156.25mV, 312.5mV,
and 625mV. All but the last provide input readings in hundredths of
millivolts. For the 625mV range, inputs are in tenths of millivolts. When
used to read millivolts, the Thermocouple Type configuration parameter
must be set to “none”.
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