GE VersaMax IC200PWR001 User Manual page 483

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 °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, defined in engineering units, which is provided in configuration
parameter Reference Junction Value.

Local Cold Junction Compensation: The best way to provide local
compensation is with an Interposing Thermocouple I/O Terminals.
(IC200CHS014), 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 I/O Terminals unit is not used, a separate thermistor must
be installed directly at the module's I/O Carrier. The thermistor must be
that supplied in kit # IC690ACC905. The thermistor must be installed at
the carrier's thermistor (+) and (–) terminals (the thermistor itself does not
have (+) and (–) markings; its orientation does not matter). Note: If Local
Compensation is selected but an Interposing Thermocouple I/O Terminals
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".
GFK-1504N Chapter 14 Temperature Sensing Modules
Analog Input, 16 Bit Thermocouple, 7 Channels
14
IC200ALG630
14-15