Spectrum Controls 1769sc-IF8u - Manual (Page 49)

Chapter 4: Module Data, Status, and Configuration 39
CJC Display
If enabled (default is disabled), all channel data is overridden with that
channel’s CJC temperature. If disabled, channel data is presented in the
input table as normal.
Cyclic Calibration
If enabled (default), the module’s internal calibration for the ADC is run
once every 5 minutes. If disabled, it is executed only once at power on/
reset and not again. Enabling this will allow the module to readjust for
environmental changes such as variations in temperature. However, the
module throughput is reduced somewhat during the calibration operation.
The user may choose to forgo calibration (and its resulting better accuracy
over time) in favor of better throughput.
CJC Sensor
If enabled (default), the CJC is read once every other module scan, and its
value updated in the CJC status word. This value is also used for
thermocouple cold junction compensation. If disabled, the CJC sensor
value is not acquired, and the CJC temperature is fixed at 25°C for all
channels. The CJC will also be fixed at 25°C for all channels if it is
determined to be broken (short or open circuit).
Configuration (Word 1)
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Ch7 Ch6 Ch5 Ch4 Ch3 Ch2 Ch1 Ch0
0 0 0 0 0 0 0 0
1 1 1 1 1 1 1 1
CH7 CH6 CH5 CH4 CH3 CH2 CH1 CH0
0 0 0 0 0 0 0 0
1 1 1 1 1 1 1 1
0 Volt CJC Adjus t
Perform CJC
No CJC Adjustment
Ope n Circuit Dis able
Enabled
Disabled
Open Circuit Disable
Setting the bit to 1 disables the open circuit detect for the associated
channel.
By default, open circuit detection is applied.
0 Volt CJC Adjust
Cold Junction Compensation (CJC) is performed by default by taking the
CJC sensor temperature value for a given channel, converting that to a
thermocouple voltage, and adding that voltage from the measured value
prior to converting to a user value.
If this bit is set for a given channel, the signal value is directly converted to
a user value (No cold junction compensation performed).