Rockwell Automation 1771-IL/B , D17716.5.91 ISOLATED ANALOG INPUT Module - Manual (Page 41)

Chapter 6
6-1
Module Calibration
In this chapter we tell you how to calibrate your module.
To calibrate your input module you will need the following tools
and equipment:
Tool or Equipment Description Model/Type Available from:
Precision Voltage Source
0-10V, 1
µ
V resolution;
Accuracy of better than 2mV
Analogic 3100, Data Precision 8200
or equivalent
Industrial Terminal and
Interconnect Cable Programming terminal for A-B
family processors Cat. No. 1770-T3 or Cat. No.
1784-T45, -T47, -T50, etc. Allen-Bradley Company
Highland Heights, OH
The analog input module is shipped already calibrated. If it becomes
necessary to recalibrate the module, you must calibrate the module in an I/O
chassis. The module must communicate with the processor and industrial
terminal.
Before calibrating the module, you must enter ladder logic into the processor
memory, so that you can send data to the module (BTW), and the processor can
read data from the module (BTR).
Calibration is accomplished using a method called “auto-calibration.”
Auto-calibration calibrates the input by generating offset and gain correction
values and storing them in EEPROM in the module. These values are read out
of EEPROM and placed in RAM memory at initialization of the module.
The auto-calibration routine operates as follows:
- Whenever a block transfer write (BTW) of length 37 is performed to the
module (any time after the module has been powered up), it interrogates
word 37 for a request for auto-calibration.
- The request can be for the following: offset calibration, gain calibration,
save operation (save to EEPROM). Note that only one bit may be set at
one time. To completely calibrate the module, three BTWs must be sent:
one for each offset, gain and save operations.
Chapter Objective
Tools and Equipment
Calibrating your Input
Module
About Auto-calibration