Rockwell Automation Publication 1756-UM540E-EN-P - December 2017
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1756-OF8I Isolated Analog Output Module
Chapter 5
The table describes the types of ramping that are possible.
The maximum rate of change in outputs is expressed in engineering units per
second (Engineering Units/second) and called the maximum ramp rate.
To see where to set Ramping, see
.
Hold for Initialization
Hold for Initialization causes outputs to hold present state until the value
commanded by the controller matches the value at the output screw terminal
within 0.1% of full scale, providing a bumpless transfer.
If Hold for Initialization is selected, outputs hold if there is an occurrence of any
of these three conditions:
•
Initial connection is established after power up.
•
A new connection is established after a communication fault occurs.
•
There is a transition to Run mode from Program state.
The
I.Ch[x].InHold
tag for a channel indicates that the channel is holding.
Clamping/Limiting
Clamping limits the output from the analog module to remain within a range
configured by the controller, even when the controller commands an output
outside that range. This safety feature sets a high clamp and a low clamp.
Once clamps are determined for a module and enabled, any data received from
the controller that exceeds those clamps sets an appropriate limit alarm and
transitions the output to that limit but not beyond the requested value.
For example, an application can set the high clamp on a module for 8V and the
low clamp for -8V. If a controller sends a value corresponding to 9V to the
module, the module applies only 8V to its screw terminals.
Ramping type
Description
Run mode ramping
When the module is in Run mode, ramping occurs to all new output values at
the MaxRampRate.
Ramp to Program mode
When the present output value changes to the Program value after a Program
command is received from the controller.
Ramp to Fault mode
When the present output value changes to the Fault value after a
communication fault occurs.
