Exponentially Weighted Moving Averages (EWMA) - Johnson Controls - Metasys - LIT-12011147 - Software Application - Controller Configuration Tool - 16.0

Controller Tool Help

Brand
Johnson Controls
Metasys
Product name
Controller Configuration Tool
Document type
User Guide
Document number
LIT-12011147
Version
16.0
Revision date
2023-10-02
Language
English

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.

Table 1. EWMA Block Inputs and Outputs

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

1 This input or output is the Default Element of the block.
2 Appears when simulating or commissioning a controller.