Allen-Bradley SLC 500 1746-NR4, User Manual

Page: 101 / 134

Chapter 7
Module Diagnostics and Troubleshooting
7–2
A failure of any channel diagnostic test causes the faulted channel status
LED to blink. All channel faults are indicated in bits 13–15 of the channel’s
status word. Channel faults are self–clearing (bits 13 and 14 of status word).
Bit 15 is not cleared until the user makes the correct change to the channel
configuration. The channel LED stops blinking and resumes steady
illumination when the fault conditions are corrected.
Important: If you clear (0) a channel enable bit (11), all channel status
information (including error information) is reset (0).
The RTD module has five LEDs (Figure 7.1). Four of these are channel
status LEDs numbered to correspond to each of the RTD/resistance input
channels, and one is a module status LED.
Figure 7.1
LED Display
0
1
2
3
INPUT
Channel LEDs
Module Status LED MODULE STATUS
CHANNEL
RTD/resistance
STATUS
Table 7.A explains the function of the channel status LEDs while the module
status LED is turned on.
Table 7.A
LED Status Description
If Module
Status
LED is:
And
Channel
Status LED
is:
Indicated Condition: Corrective Action:
On Channel Enabled No action required.
Blinking
Broken Input Condition
(open circuit for RTD or resistance
input, and short circuit for RTD
inputs only)
To determine the exact error, check the error bits
13 to 15 in the input image. Check the channel
configuration word for valid data. Make sure that
the input type is indicated correctly in bits 0–3.
ON
linkin
Out–of–Range Condition
the input type is indicated correctly in bits 0–3.
Refer to the troubleshooting flowchart on page
7–6 and to ha t r 5 for mor information.
ON
Channel Configuration Error
R f r to th troubl shootin flow hart on a
7–6 and to chapter 5 for more information.
Power–Up No action required.
Off
Channel Not Enabled
No action required. For an example of how to
enable a channel refer to chapter 6, Ladder
Programming Examples.
LED Indicators
AB Spares