29
10 Digital Input Operation
Depending on your model, the digital input can be used
to perform one of the available functions as shown in
the table below.
High = Open contacts (and 2 to 24Vdc for the isolated
digital input).
Low = Closed contacts (and <0.8Vdc for the isolated
digital input).
Controller
Digital Input
State Transition
Functions
High to
Low
Low to
High
Reset Latched Alarm(s) No Action Reset*
Control Enable/Disable Disable Enable
Auto/Manual Manual Automatic
Pre-Tune Start/Stop Stop Start*
Tune at SP Start/Stop Stop Start*
*Alarm outputs only reset if the alarm condition is no-
longer present and tuning will only start if the settings
and current process conditions allow (see tuning sec-
tion for more details)
Limiter
Digital Input State
Transition
Function
High to
Low
Low to
High
Reset Latched Limit &
Alarm(s)
No Action Reset*
*Limit and Alarm outputs only reset if the limit exceed
and/or alarm conditions are no longer present.
When the instrument is turned on, a change in the digi-
tal input signal from High Low, or Low to High will
cause the function to change (unless it is already in the
state dictated by the signal change).
The keypad can also be used to change the status of
the same function via the relevant menu. The most
recent digital input or keypad instruction will be
implemented.
The digital input is “edge sensitive”, which
means that it only reacts to a detected
transition in the input state. The device
cannot detect a status change made
when it is turned off. It also means that
if it is in the “ON” state, but the current
condition of the unit is the “OFF” state
(either because a keypad instruction or
it has powered up that way) the digital
input would first have to be set first to
OFF and then ON again before it would
set the function ON.
However, on the Limiter model if the Digital Input is in
an “ON” state at power-up it gives a Reset signal. Once
powered up the Limiter model behaves the same way
to a transition.
To Next Page
Loading...
Need help?
General
