Cold Junctions - GE Mark VIeS System Manual

Cold Junctions

Two Cold Junction temperature sensors located on the SUAA terminal board provide local cold junction temperature for Cold
Junction compensation for Thermocouple inputs. The YUAA products also supports the ability for the user to configure and
use a Remote Cold Junction. The configuration between Local/Remote Cold Junction is determined by the ColdJuncType
parameter on the YUAA Parameters tab (remote or local). The Remote cold junction value is provided by the application by
using the CJRemote variable in the Variables tab. From the Parameters tab, the TempUnits determines if the application is
using °F or °C.
In addition, support is provided for the user to specify a Backup cold junction that gets used if either the Local or Remote
Cold Junction is deemed unhealthy (out of range). The Backup Cold junction value is provided by the application by using the
CJBackup variable in the Variables tab.
The temperature units for both BackupCJ and RemoteCJ will be assumed as equivalent to the setting of the TempUnits
parameter on the Parameters tab.
Normal operation uses the two internal CJC sensors. Due to package heating variation for varying channel assignments, the
accuracy of the CJC is best when other channels are NOT assigned to high power modes such as mA outputs or internal fed
mA inputs.
Caution
YUAA Universal I/O Modules
For best accuracy it is recommended that remote cold junctions be used due to heat
dissipation from analog outputs and input modes. The remote cold junction value may
be from either RTD channels on the same YUAA with variables passed to application
code or from other devices read by the application code such as another YUAA.
Public Information
GEH-6855_Vol_II System Guide 193