Rockwell Automation 1746-NT4 Series B,D17466.6.1 SLC 500 4-Channel Thermocouple/mV Input Module User Manual - Manual (Page 93)

Publication 1746-UM007C-EN-P - July 2004
Application Examples 8-7
Program Setup and Operation Summary
1. Set up two configuration words in memory for each channel,
one for °C and the other for °F. In addition, set up two
configuration words to monitor the thermocouple’s CJC
temperature. Monitoring the CJC temperature gives a good
indication of the temperature inside of the control cabinet the
SLC is mounted in. The table below shows the configuration
word allocation summary.
2. When the positions of the degrees selector switch or
ambient/cabinet selector switch change, write the appropriate
channel configurations to the NT4 module. Note that the use of
the OSR instruction (one-shot rising) makes these configuration
changes edge-triggered, i.e. the NT4 is reconfigured only when a
selector switch changes position.
3. Monitor the channel 0 status word to determine which
temperature is being displayed (ambient or cabinet) and
energize the appropriate pilot light.
4. Convert the individual thermocouple data words to BCD and
send the data to the respective LED displays.
Program Listing
The first six rungs of the program starting on the next page send the
correct channel setup information to the NT4 module based on the
position of the two selector switches.
Channel Configuration Word Allocation
°F °C
1 N10:0 N10:4
2 N10:1 N10:5
3 N10:2 N10:6
4 N10:3 N10:7
CJC N10:8 N10:9
C F
Ambient
Cabinet
Selector Switches:
° °