Rockwell Automation 1746-NI8 SLC 500 Analog Input Modules User Manual - Manual (Page 62)

7–3 Module Diagnostics and Troubleshooting
Publication 1746Ć6.8 - April 1997
Channel Status LEDs (Green)
The channel status LED is used to indicate channel status and related
error information contained in the channel status word. This
includes conditions such as:
•
normal operation
•
channel-related configuration errors
•
open-circuit errors
•
out-of-range errors
All channel errors are recoverable errors and after corrective action,
normal operation resumes.
Invalid Channel Configuration
Whenever a channel’s configuration word is improperly defined, the
channel status LED blinks and bit 15 of the channel status word is
set. Configuration errors occur when the data format (bits 3–5 in the
channel configuration word) is invalid, or when the open-circuit state
selection (bits 6 and 7) is invalid.
OpenĆCircuit Detection
An open-circuit test is performed on all enabled channels configured
for 4–20 mA input. Whenever an open-circuit condition occurs (see
possible causes listed below), the channel status LED blinks and bit
12 of the channel status word is set.
Possible causes of an open-circuit include:
•
The sensing device may be broken.
•
A wire may be loose or cut.
•
The sensing device may not have been installed on the configured
channel.
If an open-circuit is detected, the channel data word reflects input
data as defined by the open-circuit bits (6 and 7) in the channel
configuration word.
OutĆOfĆRange Detection
Whenever the data received at the channel data word is out of the
defined operating range, an over-range or under-range error is
indicated and bit 13 (over-range) or bit 14 (under-range) of the
channel status word is set.