Output Clamping
Output 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.
IMPORTANT:
Output clamping does not apply during
Program Mode and Communication Fault Mode.
Once clamp values are set, if data received from the controller exceeds those clamps, the
following events occur:
- The output value transitions to the clamp limit but not to the requested value.
- The appropriate limit alarm is triggered.
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.
Clamping alarms are enabled by default. You can disable the alarms or configure latching
behavior of the alarms on a per channel basis.
IMPORTANT:
Clamp Limit values are in engineering units and must be recalculated when the scaling
parameters are changed. Recalculate Units in the Module Properties dialog helps to
recalculate the Clamp Limit values and all other configurations with engineering
units. Failure to update the Clamp Limit values can cause clamping not to take
effect or generate a small output signal that could be misinterpreted as a hardware
problem.
For example, an analog output module channel that uses Current (mA) output type with
Clamping enabled has the following configuration parameters:
- Scaling values:
- High Engineering = 100.0000%
- Low Engineering = 0.0000%
- Clamp Limits:
- High Clamp = 100.0000%
- Low Clamp = 0.0000%
If you change the scaling High/Low Engineering values to 2 Bar/0 Bar, the Recalculate
Units suggest changing the High/Low Clamp Limit values to 2/0 to make sure that the
application continues to operate as expected.
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