Weidmuller AMS400A - Universal interface device - Handbuch (Seite 32)

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•AnaloguetoAnalogue(“AA”)configuration
General
The PLC/computer/DCS connection to the AMS400A is an analogue
signal, i.e., a proportional current or voltage based signal. This signal
controls the analogue output to the field device in automatic mode. In
manual mode, the operator controls the output from the front panel
keypad.
Handovermode
If the controller loses control over the process, as it does when the
element is under manual control, it will compensate by adjusting its
output to either zero or full scale according to feedback it receives.
To return smoothly to automatic control after a period of manual
control, the AMS400A enters a special “handover” mode. It remains in
handover mode until its output level and the controller’s are sufficiently
close.
There are two ways to handover control back to automatic. The
AMS400A can either hold the output or ramp the output value towards
the automatic value at a predefined rate. When the two values are
close enough it can switch to automatic control.
StatusfeedbackfortheControlDevice
There are two digital connections that signal the controlling equipment
about the operating mode, i.e., auto or manual and the handover
status.
Modeshiftcontrols
The AMS400A has two mode shift inputs from the controlling
equipment. One shifts the AMS400A from Auto to Manual mode and
the other changes it from Manual to Handover mode.