AB Quality ALLEN-BRADLEY 1791 User Manual page 60

Analog block i/o input/output modules
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Important: You can calibrate all four inputs simultaneously by wiring
them in parallel.
2.
Verify normal operation.
3.
Select calibration mode, voltage input mode and the input channels
you want to calibrate.
For example, to calibrate input channel 0, set bits 15 (17), 14 (16)
and 01 of BTW word 0 (C001h).
4.
Apply 0.000V to inputs.
5.
Set the EX bit (bit 07 of BTW word 0).
For PLC systems: Monitor the DN bit (BTR word 0, bit 07) until it
is set (1).
For SLC systems: Allow at least 5 seconds before continuing.
6.
Reset (0) the EX bit (BTW word 0, bit 07) and set (1) the HL bit
(BTW word 0, bit 06).
7.
Apply full scale voltage (+10.000V) to the inputs you are calibrating.
8.
Set (1) the EX bit.
For PLC systems: Monitor the DN bit (BTR word 0, bit 07) until it
is set (1).
For SLC systems: Allow at least 5 seconds before continuing.
9.
Verify the input calibration by doing the following:
Make sure your terminal is in decimal radix mode
Important: Input values are scaled in millivolts.
Vary the input reference over +10V range.
Ensure the module input indications in the appropriate BTR words
are within acceptable limits.
Repeat steps 3–9 if necessary
Important: At this point, if you are not satisfied with your calibration, you
can cycle power to the block to restore the previous calibration constants.
If you move on to Step 10 of this procedure, the present calibration data
constants will overwrite the previous constants, making the previous
constants inaccessible.
Chapter 7
Module Calibration
7-5

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