Rockwell Automation 1762-IT4 Thermocouple/mV Input Module - Manual (Page 70)

Publication 1762-UM002A-EN-P - July 2002
4-2 Diagnostics and Troubleshooting
Stand Clear of Equipment
When troubleshooting any system problem, have all personnel remain
clear of the equipment. The problem could be intermittent, and
sudden unexpected machine motion could occur. Have someone
ready to operate an emergency stop switch in case it becomes
necessary to shut off power.
Program Alteration
There are several possible causes of alteration to the user program,
including extreme environmental conditions, Electromagnetic
Interference (EMI), improper grounding, improper wiring
connections, and unauthorized tampering. If you suspect a program
has been altered, check it against a previously saved master program.
Safety Circuits
Circuits installed on the machine for safety reasons, like over-travel
limit switches, stop push buttons, and interlocks, should always be
hard-wired to the master control relay. These devices must be wired
in series so that when any one device opens, the master control relay
is de-energized, thereby removing power to the machine. Never alter
these circuits to defeat their function. Serious injury or machine
damage could result.
Module Operation vs.
Channel Operation The module performs diagnostic operations at both the module level
and the channel level. Module-level operations include functions such
as power-up, configuration, and communication with a MicroLogix
1200 controller.
Channel-level operations describe channel related functions, such as
data conversion and over- or under-range detection.
Internal diagnostics are performed at both levels of operation. When
detected, module error conditions are immediately indicated by the
module status LED. Both module hardware and channel configuration
error conditions are reported to the controller. Channel over-range or
under-range and open-circuit conditions are reported in the module’s
input data table. Module hardware errors are typically reported in the
controller’s I/O status file. Refer to your controller manual for details.