Rockwell Automation Allen-Bradley 1794-IRT8K, User Manual

Page: 61 / 86

Publication 1794-6.5.12 - September 2011
Calibrate Your Module
49
Cold Junction Calibration
Both cold junction compensation inputs must be calibrated at at the same
time. To calibrate both at once, proceed as follows:
1. Connect 10 K
Ω
, 0.5% resistors across terminals 37 and 39 (CJC 1) and
terminals 46 and 48 (CJC 2).
2. Apply power to the module for 20 minutes before calibrating.
3. Initiate a write to the module with 2404 (hex) value in the EDT
command location (word 3, bits 00…15).
4. Monitor the EDT response location (read word 11, bits 00…15) for an
echo of the EDT command.
If the EDT response word reads 80FF (hex), repeat step 3. Make sure that
sufficient time is allowed for the module to respond to your request. If there is
no change, calibration has failed. Check the wiring and try again.
Channel Loop Compensation Calibration
Each 2-wire RTD can be calibrated individually, or at the same time. Proceed
as follows.
1. Short circuit the end of each input cable at the RTD element. Do this
for all the channels to be calibrated.
2. Apply power to the module for 20 minutes before calibrating.
3. Initiate a write to the module with 2403(hex) (calibrate all channels) in
the EDT command location (write word 3, bits 00…15). For individual
channel calibrations, use 04X3 (hex) (0403, 0413, 0423, ...0473).
4. Monitor the EDT response location (read word 1X, bits 00…15) for an
echo of the EDT command.
If the EDT response word reads 80FF (hex), repeat step 3. Make sure that
sufficient time is allowed for the module to respond to your request. If there is
no change, calibration has failed. Check the wiring and try again.
Chapter Summary
This chapter provided the user with instructions on how to calibrate your
FLEX I/O Thermocouple, RTD, and mV input module.