Publication 1769-UM002B-EN-P - July 2005
5-2 Module Diagnostics and Troubleshooting
Stand Clear of the Machine
When troubleshooting any system problem, have all personnel remain clear of
the machine. 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 to the machine.
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 program on an EEPROM or UVPROM memory module.
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 operations at two levels:
• module level
• channel level
Module-level operations include functions such as power-up, configuration,
and communication with a bus master, such as a MicroLogix 1500 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 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.
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