The CASCADE_MASTER template has a PID function block and seven alarm parameters (only PV Bad is enabled by default). It also includes a module block representing the module created from the CASCADE_SLAVE module template.
The CASCADE_SLAVE module template is part of the CASCADE_MASTER template. To configure the slave loop from the CASCADE_SLAVE template, expand the CASCADE_MASTER template and drag and drop the CASCADE_SLAVE template to the target area.
After the slave loop module has been edited, create the master loop module from CASCADE_MASTER. The procedure for customizing the master loop module is similar to that of the slave loop with one added step: the module block on the master loop's function block diagram must be converted to point to the actual slave loop module rather than to the CASCADE_SLAVE library template. To convert the module, follow these steps:
Select and right-click the module block.
Click Convert to Existing Object from the context menu.
Browse for the slave loop module you created from CASCADE_SLAVE. You might want to rename the module block to match the tag of the slave loop module, but this is optional.
The execution rate for the module created from CASCADE_MASTER is 2 seconds by default, and the slave module created from CASCADE_SLAVE defaults to 0.5 seconds.
|
Parameter |
Description |
|---|---|
|
CONTROL_OPTS |
The only control option enabled as a default is SP-PV Track in Man. Use this parameter to set the control action to Direct, when necessary. You might want to enable the option SP-PV Track in LO or IMan. |
|
GAIN |
Proportional gain tuning parameter. The default is 0.5. You might want to set a better default based on the actual loop type prior to tuning. |
|
HI_LIM |
The high alarm limit value in engineering units. This is a Quick Config parameter because the HI_ALM alarm parameter is initially disabled. |
|
IO_IN |
An I/O Reference parameter for configuring the DST for the process variable input. |
|
LO_LIM |
The low alarm limit value in engineering units. This is a Quick Config parameter because the LO_ALM alarm parameter is initially disabled. |
|
PV_SCALE |
This parameter is used to set the engineering unit value at 0 percent and 100 percent of scale for the process variable. The engineering unit descriptor can be selected from a list and the number of decimal places to be displayed can be set. Note that the number of decimal places to be displayed is applicable only for the faceplate and detail displays. The valid values for these displays are 0 to 3 decimal places. |
|
OUT_SCALE |
This parameter is used to set the engineering unit value at 0 percent and 100 percent of scale for the control output. Make sure that OUT_SCALE in the cascade master loop matches PV_SCALE in the cascade slave loop. |
|
OUT_HI_LIM |
The high limit for the control output. Typically, this value should be changed when the EU 100 percent value is changed from the default in OUT_SCALE. |
|
OUT_LO_LIM |
The low limit for the control output. Typically, this value should be changed when the EU 0 percent value is changed from the default in OUT_SCALE. |
|
RESET |
The integral time constant tuning parameter in seconds (seconds per repeat). The default is 10 seconds. You might want to set a better default based on the actual loop type prior to tuning. |
|
SP_HI_LIM |
The high limit for the setpoint. Typically, this value should be changed when the EU 100 percent value is changed from the default in PV_SCALE. |
|
SP_LO_LIM |
The low limit for the setpoint. Typically, this value should be changed when the EU 0 percent value is changed from the default in PV_SCALE. |