Rockwell Automation 1794-IT8,D17946.5.7 Thermocouple/Millivolt Input Module - Manual (Page 48)

6–6 Calibrating Your Module
Publication 1794-6.5.7 – April 1997
Read/Write Words for Calibration
Dec. Bit 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
Octal Bit 17 16 15 14 13 12 11 10 07 06 05 04 03 02 01 00
Read Word 10 0 0 0 0 0
Bad
Cal
Cal
Done
Cal
Range
0 Diagnostic Status
Pwr
Up
Bad
Struct
CJC
over CJC
Under
Write Word 0 8-Bit Calibration Mask
Cal
Clk Cal hi
Cal lo
Filter Cutoff FDF Data Type
Offset Calibration
Inputs can be calibrated one at a time or all at once. To calibrate the
offsets for all inputs at once, proceed as follows:
1. Apply power to the module for 40 minutes before calibrating.
2. Connect 0.000V across each input channel. Connect all high
signal terminals together and attach to the positive lead from the
precision voltage source. Connect all low signal terminals
together and attach to the negative lead.
3. After the connections stabilize, use a block transfer write to set
the bit(s) in the calibration mask that correspond to the channel(s)
you want to calibrate to 1. (Bits 08 through 15 in write word 0.)
4. Send another block transfer write to set the cal-clk bit (07 in write
word 0) to 1.
5. Monitor the cal-done bit (09 in read word 10). If the calibration is
successful, the cal-done bit will be set to 1. Verify that the bad-cal
bit (10 in read word 10) and the cal-range bit (08 in read word 10)
are not set (0).
6. Send another block transfer write to set the cal-clk bit (07 in write
word 0) to 0.
7. Monitor the cal-done bit (09 in read word 10). The cal-done bit
will be reset to 0.
8. If the calibration is successful, proceed to the gain calibration.