Allen-Bradley 1794-IRT8 - Offset Calibration

Publication 1794-6.5.12 - November 1997
6-6 Calibrating Your Module
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 20 minutes before calibrating.
2. Connect a precision millivolt source across each input channel. Set
the source to –320.00mV for a gain of 1. Connect all (L) signal termi-
nals together and attach to the positive lead from the precision voltage
source. Connect all (–) signal terminals together and attach to the neg-
ative lead.
3. Initiate a BTW to the module with the appropriate value in BTW
word 3, bits 00-15, as shown above.
4. Monitor the block transfer read word 10 bits 00-15 for an echo of the
EDT command.
1 7 gain= 128, input = –2.0 mV
1 8-15 not used
Gain Calibration all Channels 2 0 gain= 1, input = 320 mV
2 1 gain= 2, input = 320 mV
2 2 gain= 4, input = 110 mV
2 3 gain= 8, input = 70 mV
2 4 gain= 16, input = 29 mV
2 5 gain= 32, input = 19 mV
2 6 gain= 64, input = 4.0 mV
2 7 gain= 128, input = 2.0 mV
2 8-15 not used
Command Meaning
Data
(up nibble)
Data
(low nibble)
Meaning
Gain Selected Input (mV)
EDT Command
Hex Decimal
1 –320.00±0.160mV 2410 9232
2 0.000±0.001mV 2411 9233
4 –50.00±0.025mV 2412 9234
8 –10.00±0.005mV 2413 9235
16 –9.00±0.005mV 2414 9236
32 1.000±0.001mV 2415 9237
64 –4.000±0.002mV 2416 9238
128 –2.000±0.001mV 2417 9239
Allen-Bradley PLCs