User Manual

Rockwell Automation Publication 1756-UM540A-EN-P - May 2014 95
1756-OF8I Isolated Analog Output Module Chapter 5
Ramping/Rate Limiting
Ramping limits the speed at which an analog output signal can change. This
prevents fast transitions in the output from damaging the devices that an output
module controls. Ramping is also known as rate limiting.
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 page 133
.
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.
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.