The MSC Pre-Processor logic block provides configuration for the Multistage Controller. This block also filters the Process Variable of a PID when it is used in conjunction with the Multistage Controller to control staged (discrete) devices.
The MSC Pre-Processor is connected between the PID Pre-Processor and the PID to adjust the default tuning data based on the constraints of controlling a set of staged devices.
An external deadband is required for the process variable when using the MSC with the adaptive tuning feature of the PID. For proper configuration of the PID Pre-Processor with the MSC Pre-Processor and PID, see the Cooling Staged Outputs v51 and Heating Staged Outputs v51 modules (that is, view their logic).
The MSC Pre-Processor passes the reliability of the Process Variable input to the Present Value output. For all outputs, the last reliable value is passed when the block is unreliable.
- Reliable: Process Variable input is reliable and no error in MSC Pre-Processor algorithm.
- Unreliable: Process Variable input is not reliable at the start of MSC Pre-Processor algorithm.
The following table describes the inputs and outputs of the MSC Pre-Processor logic block.
|
Name |
Data Type |
Exposed for Connection by Default |
Description |
Default Value |
|---|---|---|---|---|
|
Inputs |
||||
|
Max Capacity Fraction |
Float |
No |
Indicates the ratio of the largest capacity device to the sum of all of the device capacities. This value is obtained from the MSC module. |
0.33% Display Precision: 100ths |
|
Min Off Time |
Float |
No |
Indicates the requested minimum time that an output must remain Off before being reactivated to an On condition following deactivation. |
120 Seconds |
|
Min On Time |
Float |
No |
Indicates the requested minimum time interval that an output must remain On before being deactivated to an Off condition following activation. |
240 Seconds |
|
Minimum Tune Band |
Float |
Yes |
Provides a value used to determine the Eff Min Tune Band if User Overwrite Minimum Tune Band is set to True. |
0.0 |
|
Process Range |
Float |
Yes |
Indicates the range of the process. |
22, 40 |
|
Process Variable |
Float |
Yes |
Indicates the value from the area being controlled. This value typically comes from a sensor or after some signal processing is passed to the MSC Pre-Processor block. |
0.0 |
|
Time Constant |
Float |
Yes |
Indicates the dominant time constant of the process. |
720 Seconds |
|
Units |
Enum |
No |
Contains the units for the Process Variable, Process Range, Minimum Tune Band, Present Value, and Eff Min Tune Band. |
°C, °F |
|
Outputs |
||||
|
Eff Min Off Time |
Float |
No |
Indicates the minimum time interval that an output must remain Off before being reactivated to an On condition following deactivation. This value is always greater than or equal to the Min Off Time. |
120 Seconds |
|
Eff Min On Time |
Float |
No |
Indicates the minimum time interval that an output must remain On before being deactivated to an Off condition following activation. This value is always greater than or equal to the Min On Time. |
240 Seconds |
|
Eff Min Tune Band |
Float |
No |
Provides the Minimum Tune Band used by the PID algorithm and the control band used by the PMAC algorithm. |
16 |
|
Eff Time Constant |
Float |
No |
Provides the time constant used by the PID and PMAC algorithms. |
720 Seconds |
|
Interval |
Float |
No |
Indicates the period for this block and for the MSC's PMAC Period. The calculation for the Interval must truncate the resulting value to an integer. |
24 Seconds |
|
Present Value 1 |
Float |
Yes |
Indicates the current output of the MSC Pre-Processor block. This value is the filtered Process Variable. |
0.0 |
|
Properties |
||||
|
Settling Time 2 |
Number |
N/A |
Indicates the amount of time for the process output to achieve ±5% of its final value. |
720 Seconds |
|
Standard Minimum Tune Band |
Boolean |
N/A |
Indicates whether to use the default calculation for the Eff Min Tune Band or to use the user-defined Minimum Tune Band to determine the Eff Min Tune Band. |
True |