The Analog Output (AO) function block assigns an output value to a field device through a specified I/O channel. The block supports mode control, signal status calculation, and simulation.
In Manual mode, the value of the output parameter (OUT) is set manually.
In Automatic mode, OUT is set automatically based on the value specified by the setpoint (SP) in engineering units and the I/O options parameter (IO_OPTS). In addition, you can limit the SP value and the rate at which a change in the SP is passed to OUT.
In Cascade mode, the cascade input connection (CAS_IN) is used to update the SP. The back calculation output (BKCAL_OUT) is wired to the back calculation input (BKCAL_IN) of the upstream block that provides CAS_IN. This provides bumpless transfer on mode changes and windup protection in the upstream block. The OUT parameter or an analog read-back value, such as valve position, is shown by the process value (PV) parameter in engineering units.
To support testing, you can enable simulation. This allows the channel feedback to be set manually.
There are no standard alarms in the Analog Output function block. Custom alarms are supported in this function block.
CAS_IN is the remote setpoint value from another function block.
BKCAL_OUT is the value and status required by the BKCAL_IN input of another block to prevent reset windup and to provide bumpless transfer to closed loop control.
OUT is the block output and status.
The following diagram shows the internal components of the Analog Output function block. The parameters may vary slightly for extended blocks.
