A Digital Input may be configured to be read as ON when no voltage is
applied to the input and be considered OFF when the LED associated with the
input is actually illuminated. This is the case when the input is 'Inverted'.
The inversion can be accomplished in two different ways. The input signal
may be inverted as it is sampled by the system. It can also be inverted as
it is reported by the system. The difference is in how other input features
perceive the input state.
The input Debounce, Latching, Counting, Metering, and Logging features
operate on the input state as it is sampled. When Inversion is applied
to the sampled input all of these features see and respond to the inverted
input state. This is useful in accommodating an input signal whose voltage
works with opposite meaning (5VDC means not active for instance).
When an application uses an input state in a sense opposite in meaning to
the signal itself, it may be appropriate to invert the reported state. In
this case input features work logically and the application is still
satisfied. In this case the Inversion is applied as a form of state
Conditioning prior to reporting.
State Alarming reflects the reported state. Counting and Metering (Usage)
alarms result from the sampled state.
Both Counting and Metering can be configured to respond to either a '0'
or '1' state. In effect these each have their own type of inversion. There
is sufficient flexibility to accommodate whatever is needed.
HELP Topics: IO/Inputs/[DIN]/Inversion