The EWMA logic block provides both signed (Input A - Input B) and absolute (ABS [Input A - Input B]) EWMA statistics for estimating a time series of values.
Use EWMA blocks for forecasting, control charts, and fault detection. The response of the calculation can be set by choosing an appropriate Process ID or by directly configuring the Time Constant of the process data (if Process ID = other).
The EWMA calculation is active when Update EWMA is set to True (in other words, when Update EWMA is False, the logic block holds the last value).
The following table describes the inputs and outputs of the EWMA logic block.
|
Name |
Data Type |
Exposed for Connection by Default |
Description |
Default Value |
|---|---|---|---|---|
|
Inputs |
||||
|
Input A |
Float |
Yes |
Indicates the value of the first input, Input A, used in the EWMA equation as previously described. |
0.0 |
|
Input B |
Float |
Yes |
Indicates the value of the second input, Input B, used in the EWMA equation as previously described. |
0.0 |
|
Process ID |
Enum |
No |
Identifies the process that the EWMA is being used to evaluate. If the Process ID is any value other than Other, the EWMA looks up the Eff Time Constant. Otherwise, the Time Constant input directly sets the Eff Time Constant. |
ZN-T |
|
Time Constant |
Float |
No |
Indicates the time required for a system to reach 63% of its final magnitude given a 100% step change. When the Process ID is Other, this input is used to specify the Eff Time Constant and thereby calculates the Interval; otherwise, it is ignored. |
720 Seconds |
|
Update EWMA |
Boolean |
No |
Indicates if the logic block should hold the last value or perform the EWMA calculations. |
True |
|
Outputs |
||||
|
Absolute EWMA |
Float |
Yes |
Indicates the second output of the EWMA block. |
0.0 |
|
EWMA 1 |
Float |
Yes |
Indicates the first output of the EWMA block. |
0.0 |
|
Properties |
||||
|
Eff Time Constant 2 |
Float |
N/A |
Indicates the actual value used for the Time Constant in determining the Interval. |
|
|
Interval2 |
Number |
N/A |
Indicates the time between expected executions. When the Eff Time Constant is changed, the EWMA re-calculates the Interval so that it is equal to 1/6th of the Time Constant (rounded to the nearest second). |
|
|
Setup Type |
Enum |
N/A |
Determines the type of calculation for the EWMA. |
Control Accuracy Set Name: EWMA Setup Type |
|
Smoothing Constant |
Float |
N/A |
Indicates the value used in the EWMA calculation. |
3.703704 E-031/270 |