Spectrum Controls 1769sc-IF8u User Manual
Page 70
60
Compact IO
™
Universal Input module
Open-Circuit Detection
On every other module scan, the module performs an open-circuit test on
all enabled channels. Whenever an open-circuit condition occurs, the
open-circuit bit for that channel is set in input data word 8. Possible causes
of an open circuit include:
•
the input device is broken
•
a wire is loose or cut
•
the input device is not installed on the configured channel
•
A thermocouple or RTD is installed incorrectly
!
Attention! When using a 4-wire RTD, an open circuit
condition is detected only if the excitation or the return are
broken.
!
Attention! Open circuit detection is not applicable to
the +/- 10 Volt range.
Non-critical vs.
Critical Module
Errors
Non-critical module errors are typically recoverable. Channel errors (over-
range or under-range errors) are non-critical. Non-critical error conditions
are indicated in the module input data table.
Critical module errors are conditions that may prevent normal or
recoverable operation of the system. When these types of errors occur,
the system typically leaves the run or program mode of operation until the
error can be dealt with. Critical module errors are indicated in Table 5.3
Extended Error Codes.