Rockwell Automation 1732E-IR4IM12R ArmorBlock Dual-Port EtherNet/IP 4-Point Thermocouple and RTD - Manual (Page 47)

Rockwell Automation Publication 1732E-UM004A-EN-E - July 2012 39
Configurable Features for the Thermocouple and RTD Input Modules Chapter 4
channels. Typically, this option should always be enabled except for systems that
have no thermoelectric effect, such as test equipment in a controlled lab.
When this parameter is set for a channel, compensation is derived from one or
more thermistors attached to the module. If not set (disabled), compensation will
come from a user-entered value (CJC Offset).
In most applications, we recommend that you use the cold junction
compensation enable option with the recommended thermistor based terminal
blocks attached to the module..
Cold Junction Compensation (CJC) Mode
When CJC is enabled, CJC Mode determines where the temperature
measurement source (thermistor) is located. The following options are available
for the user:
• Average Selected
• Channel Independent
When CJC Mode is Average Selected, all sensor channels will use an average of
the compensation determined by thermistor(s) attached to the user-selected
channel(s).
When CJC Mode is Channel Independent, each sensor channel uses the
compensation derived from a thermistor attached to the channel.
The produced cold junction compensation data is the temperature value read by
the thermistor(s), in °C, which is being applied to the reading on any channel
configured for thermistor compensation.
Cold Junction Compensation Offset
When no thermistor is attached to the module or channel, the user can specify
the CJC Offset value to be added to the CJC input during temperature
calculation. CJC Offset compensates for any inaccuracies of the CJC sensor.
Valid values range from 0…70 °C, with 0 °C as default value.
CJC Offset parameter is enabled for configuration when the CJC Enable
parameter is not checked for that channel.
Data Tables The data structure of each Assembly instance used by the Thermocouple and
RTD Input modules is defined in the tables below.
IMPORTANT If a thermistor is not detected from the specified channel(s), the produced
cold junction data indicates an error (0x8000) and no compensation is
applied.