Rockwell Automation Publication 1715-UM001J-EN-P - December 2020 257
Appendix B
1715-IB16D Digital Input Module Diagnostics
Threshold Values for Digital
Inputs
This section describes how to calculate and set threshold values for digital
inputs.
The module determines the channel state and the line fault status by
comparing the channel input voltage with defined threshold values. Line
faults, such as short circuit and wire off, can be determined by using different
input voltage values.
With this module, you can define custom threshold values or use a set of preset
default values. The types of threshold values you choose initially for the module
become inherent in each channel; you can define different thresholds for
individual channels later.
The threshold values determine which end-of-line (EOL) resistor value you
choose, and vice versa, depending on whether you choose the threshold values
first, or the EOL resistor values first.
By considering these two components—EOL resistor values and the threshold
values, we can arrive at the diagnostic settings for the module.
Figure 74 - Common EOL Device Scenario
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