Micromod MOD: 30ML Functions Data Base Reference - Manual (Page 79)

MOD 30ML Functions
BUILT-IN ANALOG INPUT BLOCK
40 CJC Mode (CJCMODE) ..................................................................................................... CWR
The mode of the cold junction compensation function is determined by configuring and/or
writing this attribute. Switching the CJC mode between auto and manual is a reportable
event. The available modes are as follows:
MANUAL 0 The cold junction compensation value can be set by the operator.
The manual mode causes CJC Result Quality to be good. The CJC
value is read from the built in circuit but is not used to update the
CJC Result.
AUTO 1 The cold junction compensation input from the sensor in the built-in
circuit is calculated and stored in the FCJC result and CJC result
fields where it is available for correction of the thermocouple input
value.
LOCAL 2 The cold junction compensation value can only be changed by the
operator. A compensation value is not read from the built-in circuit.
EXTERNAL 3 The cold junction compensation value is obtained from an external
source.
The applicability and switching functionality of the CJC Mode attribute is restricted as follows:
• The EXTERNAL mode applies only when the Input Type is THERMOCOUPLE. The
external mode is invoked by bringing a CJC signal into the AIN block from an external
source via a softwiring connection; it does not appear as a selection choice on the AIN
block edit display.
• The AUTO, MANUAL, and LOCAL modes apply only to Input 1 when the Input Type is
TC+CJC.
• The LOCAL mode is the only mode allowed for Input 2 when the Input Type is TC+CJC.
• Switching between the LOCAL mode and the AUTO or MANUAL modes by writing to the
CJC Mode attribute is not allowed.
41 Initial CJC Result (CJC) .................................................................................................... CWR
This attribute applies only when the input type is TC +CJC and CJC mode is not external.
The initial result is the value used when the block is initially downloaded. This value is
overwritten when the block first executes. Subsequent values are the result of block
evaluation. The CJC value is in degrees Celsius. However, when connected to a TI block,
the input will automatically be converted to the appropriate units. The value is writeable only
when the block is in manual, I/O is locked, or the instrument state is not run.
42 CJC Result Quality (CJCQ) ..............................................................................................– WR
This quality check is applicable only when the Input Type is TC + CJC and the CJC mode is
not LOCAL or EXTERNAL. This data quality field will go BAD if any of the block diagnostic
errors become active while the block is in auto. Writeable only when the block is in manual,
the I/O is locked or the instrument state is not run.
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