Channel diagnostics, Channel diagnostics -4, Out-of-range detection (input modules only) – Rockwell Automation 1790D-NOV2/TNOV2 CompactBlock LDX Analog Modules User Manual
Page 58: Open-circuit detection (input module only)
Publication 1790-UM001A-EN-P - March 2002
5-4 Module Diagnostics and Troubleshooting
Channel Diagnostics
When an input or output module channel is enabled, the module
performs a diagnostic check to see that the channel has been properly
configured. In addition, the module checks each channel on every
scan for configuration errors, under-range, open-circuit (input module
in 4 to 20 mA range only).
Out-of-Range Detection (Input Modules Only)
An out-of-range low test is performed on all channels configured for
4-20mA inputs. Whenever an out-of-range low condition occurs, the
status bit for that channel is set in input data word 4.
Open-Circuit Detection (Input Module Only)
The module performs an open-circuit test on all channels configured
for 4 to 20 mA inputs. Whenever an open-circuit condition occurs, the
status bit for that channel is set in input data word 4.
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 be installed on the configured
channel