Allen-Bradley SLC 500 1746-NR4, User Manual

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Chapter 7
Module Diagnostics and Troubleshooting
7–5
Out–Of–Range 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 14 of
the channel status word is set.
Important: There is no under range error for a direct resistance input
(default scaling).
For a review of the temperature range or resistance range limitations for your
input device, refer to the temperature ranges provided in Table 5.C to
Table 5.I or the user–specified range in configuration words 4–7 if
proportional counts is used.
Possible causes of an out–of–range condition include:
•
The temperature is too hot or too cold for the RTD being used.
•
Wrong RTD used for type/configuration selected.
•
Bad potentiometer or RTD.
•
Signal input from either potentiometer or RTD is beyond the user–set
scaling range.
Module Status LED (Green)
The module status LED is used to indicate module–related diagnostic or
operating errors. These non–recoverable errors may be detected at power up
or during module operation. Once in a module error state, the RTD module
no longer communicates with the SLC processor. Channels are disabled and
data words are cleared (0).
Failure of any diagnostic test places the module in a non–recoverable state.
To exit this state, cycle power. If the power cycle does not work, then call
your local distributor or Allen–Bradley for assistance.